<?xml version="1.0" encoding="US-ASCII" standalone="no"?>
    <!-- Field: Doc-Info; Name: Generator; Value: GoXBRL; Version: 3.4b -->
    <!-- Field: Doc-Info; Name: VendorURI; Value: http://www.novaworks.co -->
    <!-- Field: Doc-Info; Name: Source; Value: vista_10kMar312013.xfr; Date: 2013/07/17T17:28:20 -->
    <!-- Field: Doc-Info; Name: Status; Value: 0x8002004B -->
<link:linkbase xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:link="http://www.xbrl.org/2003/linkbase" xmlns:xbrldt="http://xbrl.org/2005/xbrldt" xmlns:xbrli="http://www.xbrl.org/2003/instance" xsi:schemaLocation="http://www.xbrl.org/2003/linkbase http://www.xbrl.org/2003/xbrl-linkbase-2003-12-31.xsd">
    <link:roleRef roleURI="http://vistagen.com/role/DocumentAndEntityInformation" xlink:href="vsta-20130331.xsd#DocumentAndEntityInformation" xlink:type="simple" />
    <link:roleRef roleURI="http://vistagen.com/role/ConsolidatedBalanceSheets" xlink:href="vsta-20130331.xsd#ConsolidatedBalanceSheets" xlink:type="simple" />
    <link:roleRef roleURI="http://vistagen.com/role/CondensedBalanceSheetsParenthetical" xlink:href="vsta-20130331.xsd#CondensedBalanceSheetsParenthetical" xlink:type="simple" />
    <link:roleRef roleURI="http://vistagen.com/role/ConsolidatedStatementsOfOperationsAndComprehensiveLoss" xlink:href="vsta-20130331.xsd#ConsolidatedStatementsOfOperationsAndComprehensiveLoss" xlink:type="simple" />
    <link:roleRef roleURI="http://vistagen.com/role/ConsolidatedStatementsOfCashFlows" xlink:href="vsta-20130331.xsd#ConsolidatedStatementsOfCashFlows" xlink:type="simple" />
    <link:roleRef roleURI="http://vistagen.com/role/ConsolidatedStatementsOfPreferredStock" xlink:href="vsta-20130331.xsd#ConsolidatedStatementsOfPreferredStock" xlink:type="simple" />
    <link:roleRef roleURI="http://vistagen.com/role/ConsolidatedStatementsOfStockholdersDeficit" xlink:href="vsta-20130331.xsd#ConsolidatedStatementsOfStockholdersDeficit" xlink:type="simple" />
    <link:roleRef roleURI="http://vistagen.com/role/DescriptionOfBusiness" xlink:href="vsta-20130331.xsd#DescriptionOfBusiness" xlink:type="simple" />
    <link:roleRef roleURI="http://vistagen.com/role/BasisOfPresentationAndGoingConcern" xlink:href="vsta-20130331.xsd#BasisOfPresentationAndGoingConcern" xlink:type="simple" />
    <link:roleRef roleURI="http://vistagen.com/role/SummaryOfSignificantAccountingPolicies" xlink:href="vsta-20130331.xsd#SummaryOfSignificantAccountingPolicies" xlink:type="simple" />
    <link:roleRef roleURI="http://vistagen.com/role/FairValueMeasurements" xlink:href="vsta-20130331.xsd#FairValueMeasurements" xlink:type="simple" />
    <link:roleRef roleURI="http://vistagen.com/role/PropertyAndEquipment" xlink:href="vsta-20130331.xsd#PropertyAndEquipment" xlink:type="simple" />
    <link:roleRef roleURI="http://vistagen.com/role/Av-101Acquisition" xlink:href="vsta-20130331.xsd#Av-101Acquisition" xlink:type="simple" />
    <link:roleRef roleURI="http://vistagen.com/role/AccruedExpenses" xlink:href="vsta-20130331.xsd#AccruedExpenses" xlink:type="simple" />
    <link:roleRef roleURI="http://vistagen.com/role/ConvertiblePromissoryNotesAndOtherNotesPayable" xlink:href="vsta-20130331.xsd#ConvertiblePromissoryNotesAndOtherNotesPayable" xlink:type="simple" />
    <link:roleRef roleURI="http://vistagen.com/role/CapitalStock" xlink:href="vsta-20130331.xsd#CapitalStock" xlink:type="simple" />
    <link:roleRef roleURI="http://vistagen.com/role/ResearchAndDevelopmentExpenses" xlink:href="vsta-20130331.xsd#ResearchAndDevelopmentExpenses" xlink:type="simple" />
    <link:roleRef roleURI="http://vistagen.com/role/IncomeTaxes" xlink:href="vsta-20130331.xsd#IncomeTaxes" xlink:type="simple" />
    <link:roleRef roleURI="http://vistagen.com/role/LicensingAndCollaborativeAgreements" xlink:href="vsta-20130331.xsd#LicensingAndCollaborativeAgreements" xlink:type="simple" />
    <link:roleRef roleURI="http://vistagen.com/role/StockOptionPlansAnd401KPlan" xlink:href="vsta-20130331.xsd#StockOptionPlansAnd401KPlan" xlink:type="simple" />
    <link:roleRef roleURI="http://vistagen.com/role/RelatedPartyTransactions" xlink:href="vsta-20130331.xsd#RelatedPartyTransactions" xlink:type="simple" />
    <link:roleRef roleURI="http://vistagen.com/role/CommitmentsContingenciesGuaranteesAndIndemnifications" xlink:href="vsta-20130331.xsd#CommitmentsContingenciesGuaranteesAndIndemnifications" xlink:type="simple" />
    <link:roleRef roleURI="http://vistagen.com/role/SubsequentEvents" xlink:href="vsta-20130331.xsd#SubsequentEvents" xlink:type="simple" />
    <link:roleRef roleURI="http://vistagen.com/role/SupplementalFinancialInformation" xlink:href="vsta-20130331.xsd#SupplementalFinancialInformation" xlink:type="simple" />
    <link:roleRef roleURI="http://vistagen.com/role/SummaryOfSignificantAccountingPoliciesPolicies" xlink:href="vsta-20130331.xsd#SummaryOfSignificantAccountingPoliciesPolicies" xlink:type="simple" />
    <link:roleRef roleURI="http://vistagen.com/role/SummaryOfSignificantAccountingPoliciesTables" xlink:href="vsta-20130331.xsd#SummaryOfSignificantAccountingPoliciesTables" xlink:type="simple" />
    <link:roleRef roleURI="http://vistagen.com/role/FairValueMeasurementsTables" xlink:href="vsta-20130331.xsd#FairValueMeasurementsTables" xlink:type="simple" />
    <link:roleRef roleURI="http://vistagen.com/role/PropertyAndEquipmentTables" xlink:href="vsta-20130331.xsd#PropertyAndEquipmentTables" xlink:type="simple" />
    <link:roleRef roleURI="http://vistagen.com/role/AccruedExpensesTables" xlink:href="vsta-20130331.xsd#AccruedExpensesTables" xlink:type="simple" />
    <link:roleRef roleURI="http://vistagen.com/role/ConvertiblePromissoryNotesAndOtherNotesPayableTables" xlink:href="vsta-20130331.xsd#ConvertiblePromissoryNotesAndOtherNotesPayableTables" xlink:type="simple" />
    <link:roleRef roleURI="http://vistagen.com/role/CapitalStockTables" xlink:href="vsta-20130331.xsd#CapitalStockTables" xlink:type="simple" />
    <link:roleRef roleURI="http://vistagen.com/role/IncomeTaxesTables" xlink:href="vsta-20130331.xsd#IncomeTaxesTables" xlink:type="simple" />
    <link:roleRef roleURI="http://vistagen.com/role/StockOptionPlansAnd401KPlanTables" xlink:href="vsta-20130331.xsd#StockOptionPlansAnd401KPlanTables" xlink:type="simple" />
    <link:roleRef roleURI="http://vistagen.com/role/CommitmentsContingenciesGuaranteesAndIndemnificationsTables" xlink:href="vsta-20130331.xsd#CommitmentsContingenciesGuaranteesAndIndemnificationsTables" xlink:type="simple" />
    <link:roleRef roleURI="http://vistagen.com/role/SubsequentEventsTables" xlink:href="vsta-20130331.xsd#SubsequentEventsTables" xlink:type="simple" />
    <link:roleRef roleURI="http://vistagen.com/role/SupplementalFinancialInformationTables" xlink:href="vsta-20130331.xsd#SupplementalFinancialInformationTables" xlink:type="simple" />
    <link:roleRef roleURI="http://vistagen.com/role/DescriptionOfBusinessDetailsTextuals" xlink:href="vsta-20130331.xsd#DescriptionOfBusinessDetailsTextuals" xlink:type="simple" />
    <link:roleRef roleURI="http://vistagen.com/role/BasisOfPresentationAndGoingConcernDetailsTextuals" xlink:href="vsta-20130331.xsd#BasisOfPresentationAndGoingConcernDetailsTextuals" xlink:type="simple" />
    <link:roleRef roleURI="http://vistagen.com/role/SummaryOfSignificantAccountingPoliciesDetails" xlink:href="vsta-20130331.xsd#SummaryOfSignificantAccountingPoliciesDetails" xlink:type="simple" />
    <link:roleRef roleURI="http://vistagen.com/role/FairValueMeasurementsDetails" xlink:href="vsta-20130331.xsd#FairValueMeasurementsDetails" xlink:type="simple" />
    <link:roleRef roleURI="http://vistagen.com/role/FairValueMeasurementsDetailsTextuals" xlink:href="vsta-20130331.xsd#FairValueMeasurementsDetailsTextuals" xlink:type="simple" />
    <link:roleRef roleURI="http://vistagen.com/role/PropertyAndEquipmentDetails" xlink:href="vsta-20130331.xsd#PropertyAndEquipmentDetails" xlink:type="simple" />
    <link:roleRef roleURI="http://vistagen.com/role/Av-101AcquisitionDetailsTextuals" xlink:href="vsta-20130331.xsd#Av-101AcquisitionDetailsTextuals" xlink:type="simple" />
    <link:roleRef roleURI="http://vistagen.com/role/AccruedExpensesDetails" xlink:href="vsta-20130331.xsd#AccruedExpensesDetails" xlink:type="simple" />
    <link:roleRef roleURI="http://vistagen.com/role/ConvertiblePromissoryNotesAndOtherNotesPayableDetails" xlink:href="vsta-20130331.xsd#ConvertiblePromissoryNotesAndOtherNotesPayableDetails" xlink:type="simple" />
    <link:roleRef roleURI="http://vistagen.com/role/ConvertiblePromissoryNotesAndOtherNotesPayableDetails2" xlink:href="vsta-20130331.xsd#ConvertiblePromissoryNotesAndOtherNotesPayableDetails2" xlink:type="simple" />
    <link:roleRef roleURI="http://vistagen.com/role/ConvertiblePromissoryNotesAndOtherNotesPayableDetails1" xlink:href="vsta-20130331.xsd#ConvertiblePromissoryNotesAndOtherNotesPayableDetails1" xlink:type="simple" />
    <link:roleRef roleURI="http://vistagen.com/role/ConvertiblePromissoryNotesAndOtherNotesPayableDetailsTextuals" xlink:href="vsta-20130331.xsd#ConvertiblePromissoryNotesAndOtherNotesPayableDetailsTextuals" xlink:type="simple" />
    <link:roleRef roleURI="http://vistagen.com/role/ConvertiblePromissoryNotesAndOtherNotesPayableDetailsTextuals2" xlink:href="vsta-20130331.xsd#ConvertiblePromissoryNotesAndOtherNotesPayableDetailsTextuals2" xlink:type="simple" />
    <link:roleRef roleURI="http://vistagen.com/role/CapitalStockDetails" xlink:href="vsta-20130331.xsd#CapitalStockDetails" xlink:type="simple" />
    <link:roleRef roleURI="http://vistagen.com/role/CapitalStockDetails1" xlink:href="vsta-20130331.xsd#CapitalStockDetails1" xlink:type="simple" />
    <link:roleRef roleURI="http://vistagen.com/role/CapitalStockDetails2" xlink:href="vsta-20130331.xsd#CapitalStockDetails2" xlink:type="simple" />
    <link:roleRef roleURI="http://vistagen.com/role/CapitalStockDetailsTextuals" xlink:href="vsta-20130331.xsd#CapitalStockDetailsTextuals" xlink:type="simple" />
    <link:roleRef roleURI="http://vistagen.com/role/ResearchAndDevelopmentExpensesDetailsNarrative" xlink:href="vsta-20130331.xsd#ResearchAndDevelopmentExpensesDetailsNarrative" xlink:type="simple" />
    <link:roleRef roleURI="http://vistagen.com/role/IncomeTaxesDetails" xlink:href="vsta-20130331.xsd#IncomeTaxesDetails" xlink:type="simple" />
    <link:roleRef roleURI="http://vistagen.com/role/IncomeTaxesDetails1" xlink:href="vsta-20130331.xsd#IncomeTaxesDetails1" xlink:type="simple" />
    <link:roleRef roleURI="http://vistagen.com/role/IncomeTaxesDetailsNarrative" xlink:href="vsta-20130331.xsd#IncomeTaxesDetailsNarrative" xlink:type="simple" />
    <link:roleRef roleURI="http://vistagen.com/role/StockOptionPlansAnd401KPlanDetails" xlink:href="vsta-20130331.xsd#StockOptionPlansAnd401KPlanDetails" xlink:type="simple" />
    <link:roleRef roleURI="http://vistagen.com/role/StockOptionPlansAnd401KPlanDetails1" xlink:href="vsta-20130331.xsd#StockOptionPlansAnd401KPlanDetails1" xlink:type="simple" />
    <link:roleRef roleURI="http://vistagen.com/role/RelatedPartyTransactionsDetailsTextuals" xlink:href="vsta-20130331.xsd#RelatedPartyTransactionsDetailsTextuals" xlink:type="simple" />
    <link:roleRef roleURI="http://vistagen.com/role/CommitmentsContingenciesGuaranteesAndIndemnificationsDetails" xlink:href="vsta-20130331.xsd#CommitmentsContingenciesGuaranteesAndIndemnificationsDetails" xlink:type="simple" />
    <link:roleRef roleURI="http://vistagen.com/role/CommitmentsContingenciesGuaranteesAndIndemnificationsDetails1" xlink:href="vsta-20130331.xsd#CommitmentsContingenciesGuaranteesAndIndemnificationsDetails1" xlink:type="simple" />
    <link:roleRef roleURI="http://vistagen.com/role/CommitmentsContingenciesGuaranteesAndIndemnificationsDetails2" xlink:href="vsta-20130331.xsd#CommitmentsContingenciesGuaranteesAndIndemnificationsDetails2" xlink:type="simple" />
    <link:roleRef roleURI="http://vistagen.com/role/CommitmentsContingenciesGuaranteesAndIndemnificationsDetailsNarrative" xlink:href="vsta-20130331.xsd#CommitmentsContingenciesGuaranteesAndIndemnificationsDetailsNarrative" xlink:type="simple" />
    <link:roleRef roleURI="http://vistagen.com/role/SubsequentEventsDetails" xlink:href="vsta-20130331.xsd#SubsequentEventsDetails" xlink:type="simple" />
    <link:roleRef roleURI="http://vistagen.com/role/SupplementalFinancialInformationDetailsNarrative" xlink:href="vsta-20130331.xsd#SupplementalFinancialInformationDetailsNarrative" xlink:type="simple" />
    <link:roleRef roleURI="http://vistagen.com/role/SupplementalFinancialInformationDetails" xlink:href="vsta-20130331.xsd#SupplementalFinancialInformationDetails" xlink:type="simple" />
    <link:arcroleRef xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#hypercube-dimension" arcroleURI="http://xbrl.org/int/dim/arcrole/hypercube-dimension" />
    <link:arcroleRef xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#dimension-domain" arcroleURI="http://xbrl.org/int/dim/arcrole/dimension-domain" />
    <link:arcroleRef xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#domain-member" arcroleURI="http://xbrl.org/int/dim/arcrole/domain-member" />
    <link:arcroleRef xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#all" arcroleURI="http://xbrl.org/int/dim/arcrole/all" />
    <link:arcroleRef xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#notAll" arcroleURI="http://xbrl.org/int/dim/arcrole/notAll" />
    <link:arcroleRef xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#dimension-default" arcroleURI="http://xbrl.org/int/dim/arcrole/dimension-default" />
    <link:definitionLink xlink:type="extended" xlink:role="http://vistagen.com/role/DocumentAndEntityInformation" xlink:title="0001 - Document - Document and Entity Information" />
    <link:definitionLink xlink:type="extended" xlink:role="http://vistagen.com/role/ConsolidatedBalanceSheets" xlink:title="0002 - Statement - CONSOLIDATED BALANCE SHEETS" />
    <link:definitionLink xlink:type="extended" xlink:role="http://vistagen.com/role/CondensedBalanceSheetsParenthetical" xlink:title="0003 - Statement - CONDENSED BALANCE SHEETS (Parenthetical)" />
    <link:definitionLink xlink:type="extended" xlink:role="http://vistagen.com/role/ConsolidatedStatementsOfOperationsAndComprehensiveLoss" xlink:title="0004 - Statement - CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS" />
    <link:definitionLink xlink:type="extended" xlink:role="http://vistagen.com/role/ConsolidatedStatementsOfCashFlows" xlink:title="0005 - Statement - CONSOLIDATED STATEMENTS OF CASH FLOWS" />
    <link:definitionLink xlink:type="extended" xlink:role="http://vistagen.com/role/ConsolidatedStatementsOfPreferredStock" xlink:title="0006 - Statement - CONSOLIDATED STATEMENTS OF PREFERRED STOCK">
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_StatementLineItems" xlink:label="loc_VSTAStatementLineItems" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_StatementTable" xlink:label="loc_VSTAStatementTable" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xbrldt:contextElement="segment" xlink:from="loc_VSTAStatementLineItems" xlink:to="loc_VSTAStatementTable" xlink:type="arc" order="10" xbrldt:closed="true" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_StatementEquityComponentsAxis" xlink:label="loc_VSTAStatementEquityComponentsAxis" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_VSTAStatementTable" xlink:to="loc_VSTAStatementEquityComponentsAxis" xlink:type="arc" order="1" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_EquityComponentDomain" xlink:label="loc_VSTAEquityComponentDomain" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_VSTAStatementEquityComponentsAxis" xlink:to="loc_VSTAEquityComponentDomain" xlink:type="arc" order="20" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_EquityComponentDomain" xlink:label="loc_VSTAEquityComponentDomain_10" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xbrldt:contextElement="segment" xlink:from="loc_VSTAStatementEquityComponentsAxis" xlink:to="loc_VSTAEquityComponentDomain_10" xlink:type="arc" order="30" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_PreferredStockMember" xlink:label="loc_VSTAPreferredStockMember_0" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAEquityComponentDomain" xlink:to="loc_VSTAPreferredStockMember_0" xlink:type="arc" order="1" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_SeriesAPreferredStockMember" xlink:label="loc_VSTASeriesAPreferredStockMember_10" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAEquityComponentDomain" xlink:to="loc_VSTASeriesAPreferredStockMember_10" xlink:type="arc" order="11" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_SeriesBPreferredStockMember" xlink:label="loc_VSTASeriesBPreferredStockMember_20" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAEquityComponentDomain" xlink:to="loc_VSTASeriesBPreferredStockMember_20" xlink:type="arc" order="21" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_SeriesB1PreferredStockMember" xlink:label="loc_VSTASeriesB1PreferredStockMember_30" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAEquityComponentDomain" xlink:to="loc_VSTASeriesB1PreferredStockMember_30" xlink:type="arc" order="31" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_SeriesCPreferredStockMember" xlink:label="loc_VSTASeriesCPreferredStockMember_40" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAEquityComponentDomain" xlink:to="loc_VSTASeriesCPreferredStockMember_40" xlink:type="arc" order="41" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_StockholdersEquityForPreferredStock" xlink:label="loc_VSTAStockholdersEquityForPreferredStock_70" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAStatementLineItems" xlink:to="loc_VSTAStockholdersEquityForPreferredStock_70" xlink:type="arc" order="2" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_SharesIssuedForPreferredStock" xlink:label="loc_VSTASharesIssuedForPreferredStock_70" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAStatementLineItems" xlink:to="loc_VSTASharesIssuedForPreferredStock_70" xlink:type="arc" order="3" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_IssuanceOfSeriesaPreferredStockAt2.302PerShareForCashNetOfIssuanceCostsOf24000Amount" xlink:label="loc_VSTAIssuanceOfSeriesaPreferredStockAt2.302PerShareForCashNetOfIssuanceCostsOf24000Amount_70" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAStatementLineItems" xlink:to="loc_VSTAIssuanceOfSeriesaPreferredStockAt2.302PerShareForCashNetOfIssuanceCostsOf24000Amount_70" xlink:type="arc" order="5" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_IssuanceOfSeriesaPreferredStockAt2.302PerShareForCashNetOfIssuanceCostsOf24000Shares" xlink:label="loc_VSTAIssuanceOfSeriesaPreferredStockAt2.302PerShareForCashNetOfIssuanceCostsOf24000Shares_70" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAStatementLineItems" xlink:to="loc_VSTAIssuanceOfSeriesaPreferredStockAt2.302PerShareForCashNetOfIssuanceCostsOf24000Shares_70" xlink:type="arc" order="6" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_IssuanceOfSeriesaPreferredStockAt2.302PerShareForCashNetOfIssuanceCostsOf5500Amount" xlink:label="loc_VSTAIssuanceOfSeriesaPreferredStockAt2.302PerShareForCashNetOfIssuanceCostsOf5500Amount_70" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAStatementLineItems" xlink:to="loc_VSTAIssuanceOfSeriesaPreferredStockAt2.302PerShareForCashNetOfIssuanceCostsOf5500Amount_70" xlink:type="arc" order="7" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_IssuanceOfSeriesaPreferredStockAt2.302PerShareForCashNetOfIssuanceCostsOf5500Shares" xlink:label="loc_VSTAIssuanceOfSeriesaPreferredStockAt2.302PerShareForCashNetOfIssuanceCostsOf5500Shares_70" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAStatementLineItems" xlink:to="loc_VSTAIssuanceOfSeriesaPreferredStockAt2.302PerShareForCashNetOfIssuanceCostsOf5500Shares_70" xlink:type="arc" order="8" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_IssuanceOfSeriesBPreferredStockat5.545PerShareForCashIncludingConversionOf575000FaceValueOf7ConvertibleNotesPlusAccruedInterestOf3800NetOfUnamortizedDiscountOf70800AndIssuanceCostsOf39800Amount" xlink:label="loc_VSTAIssuanceOfSeriesBPreferredStockat5.545PerShareForCashIncludingConversionOf575000FaceValueOf7ConvertibleNotesPlusAccruedInterestOf3800NetOfUnamortizedDiscountOf70800AndIssuanceCostsOf39800Amount_70" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAStatementLineItems" xlink:to="loc_VSTAIssuanceOfSeriesBPreferredStockat5.545PerShareForCashIncludingConversionOf575000FaceValueOf7ConvertibleNotesPlusAccruedInterestOf3800NetOfUnamortizedDiscountOf70800AndIssuanceCostsOf39800Amount_70" xlink:type="arc" order="9" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_IssuanceOfSeriesBPreferredStockat5.545PerShareForCashIncludingConversionOf575000FaceValueOf7ConvertibleNotesPlusAccruedInterestOf3800NetOfUnamortizedDiscountOf70800AndIssuanceCostsOf39800Shares" xlink:label="loc_VSTAIssuanceOfSeriesBPreferredStockat5.545PerShareForCashIncludingConversionOf575000FaceValueOf7ConvertibleNotesPlusAccruedInterestOf3800NetOfUnamortizedDiscountOf70800AndIssuanceCostsOf39800Shares_70" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAStatementLineItems" xlink:to="loc_VSTAIssuanceOfSeriesBPreferredStockat5.545PerShareForCashIncludingConversionOf575000FaceValueOf7ConvertibleNotesPlusAccruedInterestOf3800NetOfUnamortizedDiscountOf70800AndIssuanceCostsOf39800Shares_70" xlink:type="arc" order="10" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_IssuanceOfSeriesbPreferredStockat5.545PerShareForCashNetOfissuanceCostsOf97200Amount" xlink:label="loc_VSTAIssuanceOfSeriesbPreferredStockat5.545PerShareForCashNetOfissuanceCostsOf97200Amount_70" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAStatementLineItems" xlink:to="loc_VSTAIssuanceOfSeriesbPreferredStockat5.545PerShareForCashNetOfissuanceCostsOf97200Amount_70" xlink:type="arc" order="11" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_IssuanceOfSeriesbPreferredStockat5.545PerShareForCashNetOfissuanceCostsOf97200Shares" xlink:label="loc_VSTAIssuanceOfSeriesbPreferredStockat5.545PerShareForCashNetOfissuanceCostsOf97200Shares_70" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAStatementLineItems" xlink:to="loc_VSTAIssuanceOfSeriesbPreferredStockat5.545PerShareForCashNetOfissuanceCostsOf97200Shares_70" xlink:type="arc" order="12" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_IssuanceOfSeriesb1PreferredStockat5.545ForAcquiredInprocessresearchAndDevelopmentAmount" xlink:label="loc_VSTAIssuanceOfSeriesb1PreferredStockat5.545ForAcquiredInprocessresearchAndDevelopmentAmount_70" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAStatementLineItems" xlink:to="loc_VSTAIssuanceOfSeriesb1PreferredStockat5.545ForAcquiredInprocessresearchAndDevelopmentAmount_70" xlink:type="arc" order="13" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_IssuanceOfSeriesb1PreferredStockat5.545ForAcquiredInprocessresearchAndDevelopmentShares" xlink:label="loc_VSTAIssuanceOfSeriesb1PreferredStockat5.545ForAcquiredInprocessresearchAndDevelopmentShares_70" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAStatementLineItems" xlink:to="loc_VSTAIssuanceOfSeriesb1PreferredStockat5.545ForAcquiredInprocessresearchAndDevelopmentShares_70" xlink:type="arc" order="14" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_IssuanceOfSeriesCPreferredStockAt6.00PerShareForCashIncludingConversionOf1655000FaceValueOf10ConvertibleNotesPlusAccruedInterestOf408600NetOfUnamortizedNote" xlink:label="loc_VSTAIssuanceOfSeriesCPreferredStockAt6.00PerShareForCashIncludingConversionOf1655000FaceValueOf10ConvertibleNotesPlusAccruedInterestOf408600NetOfUnamortizedNote_70" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAStatementLineItems" xlink:to="loc_VSTAIssuanceOfSeriesCPreferredStockAt6.00PerShareForCashIncludingConversionOf1655000FaceValueOf10ConvertibleNotesPlusAccruedInterestOf408600NetOfUnamortizedNote_70" xlink:type="arc" order="15" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_IssuanceOfSeriesCPreferredStockAt6.00PerShareForCashIncludingConversionOf1655000FaceValueOf10ConvertibleNotesPlusAccruedInterestOf408600NetOfUnamortizedShares" xlink:label="loc_VSTAIssuanceOfSeriesCPreferredStockAt6.00PerShareForCashIncludingConversionOf1655000FaceValueOf10ConvertibleNotesPlusAccruedInterestOf408600NetOfUnamortizedShares_70" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAStatementLineItems" xlink:to="loc_VSTAIssuanceOfSeriesCPreferredStockAt6.00PerShareForCashIncludingConversionOf1655000FaceValueOf10ConvertibleNotesPlusAccruedInterestOf408600NetOfUnamortizedShares_70" xlink:type="arc" order="16" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_ProceedsAllocatedToWarrantsIssuedInConnectionWithSeriesCPreferredstockAmount" xlink:label="loc_VSTAProceedsAllocatedToWarrantsIssuedInConnectionWithSeriesCPreferredstockAmount_70" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAStatementLineItems" xlink:to="loc_VSTAProceedsAllocatedToWarrantsIssuedInConnectionWithSeriesCPreferredstockAmount_70" xlink:type="arc" order="17" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_ProceedsAllocatedToWarrantsIssuedInConnectionWithSeriesCPreferredstockShares" xlink:label="loc_VSTAProceedsAllocatedToWarrantsIssuedInConnectionWithSeriesCPreferredstockShares_70" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAStatementLineItems" xlink:to="loc_VSTAProceedsAllocatedToWarrantsIssuedInConnectionWithSeriesCPreferredstockShares_70" xlink:type="arc" order="18" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_IssuanceOfSeriescPreferredStockat6.00PerShareForCashNetOfissuanceCostsOf20700Amount" xlink:label="loc_VSTAIssuanceOfSeriescPreferredStockat6.00PerShareForCashNetOfissuanceCostsOf20700Amount_70" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAStatementLineItems" xlink:to="loc_VSTAIssuanceOfSeriescPreferredStockat6.00PerShareForCashNetOfissuanceCostsOf20700Amount_70" xlink:type="arc" order="19" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_IssuanceOfSeriescPreferredStockat6.00PerShareForCashNetOfissuanceCostsOf20700Shares" xlink:label="loc_VSTAIssuanceOfSeriescPreferredStockat6.00PerShareForCashNetOfissuanceCostsOf20700Shares_70" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAStatementLineItems" xlink:to="loc_VSTAIssuanceOfSeriescPreferredStockat6.00PerShareForCashNetOfissuanceCostsOf20700Shares_70" xlink:type="arc" order="20" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_IssuanceOfSeriescPreferredStockAt6.00PerShareForServicesAndInPaymentOfInterestOnLineOfCreditAmount" xlink:label="loc_VSTAIssuanceOfSeriescPreferredStockAt6.00PerShareForServicesAndInPaymentOfInterestOnLineOfCreditAmount_70" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAStatementLineItems" xlink:to="loc_VSTAIssuanceOfSeriescPreferredStockAt6.00PerShareForServicesAndInPaymentOfInterestOnLineOfCreditAmount_70" xlink:type="arc" order="21" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_IssuanceOfSeriescPreferredStockAt6.00PerShareForServicesAndInPaymentOfInterestOnLineOfCreditShares" xlink:label="loc_VSTAIssuanceOfSeriescPreferredStockAt6.00PerShareForServicesAndInPaymentOfInterestOnLineOfCreditShares_70" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAStatementLineItems" xlink:to="loc_VSTAIssuanceOfSeriescPreferredStockAt6.00PerShareForServicesAndInPaymentOfInterestOnLineOfCreditShares_70" xlink:type="arc" order="22" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_ConversionOfAllSeriesOfPreferredStockIntoVistagenCommonStockInConnectionWithMergerAmount" xlink:label="loc_VSTAConversionOfAllSeriesOfPreferredStockIntoVistagenCommonStockInConnectionWithMergerAmount_70" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAStatementLineItems" xlink:to="loc_VSTAConversionOfAllSeriesOfPreferredStockIntoVistagenCommonStockInConnectionWithMergerAmount_70" xlink:type="arc" order="23" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_ConversionOfAllSeriesOfPreferredStockIntoVistagenCommonStockInConnectionWithMergerShares" xlink:label="loc_VSTAConversionOfAllSeriesOfPreferredStockIntoVistagenCommonStockInConnectionWithMergerShares_70" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAStatementLineItems" xlink:to="loc_VSTAConversionOfAllSeriesOfPreferredStockIntoVistagenCommonStockInConnectionWithMergerShares_70" xlink:type="arc" order="24" />
    </link:definitionLink>
    <link:definitionLink xlink:type="extended" xlink:role="http://vistagen.com/role/ConsolidatedStatementsOfStockholdersDeficit" xlink:title="0007 - Statement - CONSOLIDATED STATEMENTS OF STOCKHOLDERS' DEFICIT">
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_StatementLineItems" xlink:label="loc_VSTAStatementLineItems" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_StatementTable" xlink:label="loc_VSTAStatementTable" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xbrldt:contextElement="segment" xlink:from="loc_VSTAStatementLineItems" xlink:to="loc_VSTAStatementTable" xlink:type="arc" order="10" xbrldt:closed="true" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_StatementEquityComponentsAxis" xlink:label="loc_VSTAStatementEquityComponentsAxis" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_VSTAStatementTable" xlink:to="loc_VSTAStatementEquityComponentsAxis" xlink:type="arc" order="1" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_EquityComponentDomain" xlink:label="loc_VSTAEquityComponentDomain" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_VSTAStatementEquityComponentsAxis" xlink:to="loc_VSTAEquityComponentDomain" xlink:type="arc" order="20" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_EquityComponentDomain" xlink:label="loc_VSTAEquityComponentDomain_10" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xbrldt:contextElement="segment" xlink:from="loc_VSTAStatementEquityComponentsAxis" xlink:to="loc_VSTAEquityComponentDomain_10" xlink:type="arc" order="30" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_SeriesAPreferredStockMember" xlink:label="loc_VSTASeriesAPreferredStockMember_0" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAEquityComponentDomain" xlink:to="loc_VSTASeriesAPreferredStockMember_0" xlink:type="arc" order="1" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_CommonStockMember" xlink:label="loc_VSTACommonStockMember_10" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAEquityComponentDomain" xlink:to="loc_VSTACommonStockMember_10" xlink:type="arc" order="11" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_AdditionalPaidInCapitalMember" xlink:label="loc_VSTAAdditionalPaidInCapitalMember_20" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAEquityComponentDomain" xlink:to="loc_VSTAAdditionalPaidInCapitalMember_20" xlink:type="arc" order="21" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_TreasuryStockMember" xlink:label="loc_VSTATreasuryStockMember_30" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAEquityComponentDomain" xlink:to="loc_VSTATreasuryStockMember_30" xlink:type="arc" order="31" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_NotesReceivableFromSaleOfStockMember" xlink:label="loc_VSTANotesReceivableFromSaleOfStockMember_40" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAEquityComponentDomain" xlink:to="loc_VSTANotesReceivableFromSaleOfStockMember_40" xlink:type="arc" order="41" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_DeficitAccumulatedDuringTheDevelopmentStageMember" xlink:label="loc_VSTADeficitAccumulatedDuringTheDevelopmentStageMember_50" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAEquityComponentDomain" xlink:to="loc_VSTADeficitAccumulatedDuringTheDevelopmentStageMember_50" xlink:type="arc" order="51" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_StockholdersEquity" xlink:label="loc_VSTAStockholdersEquity_80" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAStatementLineItems" xlink:to="loc_VSTAStockholdersEquity_80" xlink:type="arc" order="2" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_SharesIssued" xlink:label="loc_VSTASharesIssued_80" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAStatementLineItems" xlink:to="loc_VSTASharesIssued_80" xlink:type="arc" order="3" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_InitialSaleOfCommonStockForCashToFounderAmount" xlink:label="loc_VSTAInitialSaleOfCommonStockForCashToFounderAmount_80" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAStatementLineItems" xlink:to="loc_VSTAInitialSaleOfCommonStockForCashToFounderAmount_80" xlink:type="arc" order="5" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_InitialSaleOfCommonStockForCashToFounderShares" xlink:label="loc_VSTAInitialSaleOfCommonStockForCashToFounderShares_80" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAStatementLineItems" xlink:to="loc_VSTAInitialSaleOfCommonStockForCashToFounderShares_80" xlink:type="arc" order="6" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_FairValueOfCommonStockIssuedForServicesAmount" xlink:label="loc_VSTAFairValueOfCommonStockIssuedForServicesAmount_80" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAStatementLineItems" xlink:to="loc_VSTAFairValueOfCommonStockIssuedForServicesAmount_80" xlink:type="arc" order="7" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_FairValueOfCommonStockIssuedForServicesShares" xlink:label="loc_VSTAFairValueOfCommonStockIssuedForServicesShares_80" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAStatementLineItems" xlink:to="loc_VSTAFairValueOfCommonStockIssuedForServicesShares_80" xlink:type="arc" order="8" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_EffectOfMergerAmount" xlink:label="loc_VSTAEffectOfMergerAmount_80" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAStatementLineItems" xlink:to="loc_VSTAEffectOfMergerAmount_80" xlink:type="arc" order="9" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_EffectOfMergerShares" xlink:label="loc_VSTAEffectOfMergerShares_80" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAStatementLineItems" xlink:to="loc_VSTAEffectOfMergerShares_80" xlink:type="arc" order="10" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_SaleOfCommonStockForCashAmount" xlink:label="loc_VSTASaleOfCommonStockForCashAmount_80" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAStatementLineItems" xlink:to="loc_VSTASaleOfCommonStockForCashAmount_80" xlink:type="arc" order="11" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_SaleOfCommonStockForCashShares" xlink:label="loc_VSTASaleOfCommonStockForCashShares_80" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAStatementLineItems" xlink:to="loc_VSTASaleOfCommonStockForCashShares_80" xlink:type="arc" order="12" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_FairValueOfWarrantsIssuedForServices" xlink:label="loc_VSTAFairValueOfWarrantsIssuedForServices_80" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAStatementLineItems" xlink:to="loc_VSTAFairValueOfWarrantsIssuedForServices_80" xlink:type="arc" order="13" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_CommonStockIssuedUponExerciseOfOptionsFrom1999StockIncentivePlanAmount" xlink:label="loc_VSTACommonStockIssuedUponExerciseOfOptionsFrom1999StockIncentivePlanAmount_80" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAStatementLineItems" xlink:to="loc_VSTACommonStockIssuedUponExerciseOfOptionsFrom1999StockIncentivePlanAmount_80" xlink:type="arc" order="14" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_CommonStockIssuedUponExerciseOfOptionsFrom1999StockIncentivePlanShares" xlink:label="loc_VSTACommonStockIssuedUponExerciseOfOptionsFrom1999StockIncentivePlanShares_80" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAStatementLineItems" xlink:to="loc_VSTACommonStockIssuedUponExerciseOfOptionsFrom1999StockIncentivePlanShares_80" xlink:type="arc" order="15" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_ProceedsAllocatedToWarrantsIssuedInConnectionWith7ConvertibleNotes" xlink:label="loc_VSTAProceedsAllocatedToWarrantsIssuedInConnectionWith7ConvertibleNotes_80" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAStatementLineItems" xlink:to="loc_VSTAProceedsAllocatedToWarrantsIssuedInConnectionWith7ConvertibleNotes_80" xlink:type="arc" order="16" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_ProceedsAllocatedToWarrantsIssuedInConnectionWith10ConvertibleNotes" xlink:label="loc_VSTAProceedsAllocatedToWarrantsIssuedInConnectionWith10ConvertibleNotes_80" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAStatementLineItems" xlink:to="loc_VSTAProceedsAllocatedToWarrantsIssuedInConnectionWith10ConvertibleNotes_80" xlink:type="arc" order="17" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_ProceedsAllocatedToWarrantsIssuedInConnectionWithSeriescPreferredStock" xlink:label="loc_VSTAProceedsAllocatedToWarrantsIssuedInConnectionWithSeriescPreferredStock_80" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAStatementLineItems" xlink:to="loc_VSTAProceedsAllocatedToWarrantsIssuedInConnectionWithSeriescPreferredStock_80" xlink:type="arc" order="18" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_CommonStockIssuedUponExerciseOfOptionsFrom1999StockIncentivePlanAndWarrantsForCashAmount" xlink:label="loc_VSTACommonStockIssuedUponExerciseOfOptionsFrom1999StockIncentivePlanAndWarrantsForCashAmount_80" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAStatementLineItems" xlink:to="loc_VSTACommonStockIssuedUponExerciseOfOptionsFrom1999StockIncentivePlanAndWarrantsForCashAmount_80" xlink:type="arc" order="19" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_CommonStockIssuedUponExerciseOfOptionsFrom1999StockIncentivePlanAndWarrantsForCashShares" xlink:label="loc_VSTACommonStockIssuedUponExerciseOfOptionsFrom1999StockIncentivePlanAndWarrantsForCashShares_80" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAStatementLineItems" xlink:to="loc_VSTACommonStockIssuedUponExerciseOfOptionsFrom1999StockIncentivePlanAndWarrantsForCashShares_80" xlink:type="arc" order="20" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_CommonStockIssuedUponExerciseOfOptionsFrom1999StockIncentivePlanAndWarrantsForDebtCancellationAmount" xlink:label="loc_VSTACommonStockIssuedUponExerciseOfOptionsFrom1999StockIncentivePlanAndWarrantsForDebtCancellationAmount_80" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAStatementLineItems" xlink:to="loc_VSTACommonStockIssuedUponExerciseOfOptionsFrom1999StockIncentivePlanAndWarrantsForDebtCancellationAmount_80" xlink:type="arc" order="21" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_CommonStockIssuedUponExerciseOfOptionsFrom1999StockIncentivePlanAndWarrantsForDebtCancellationShares" xlink:label="loc_VSTACommonStockIssuedUponExerciseOfOptionsFrom1999StockIncentivePlanAndWarrantsForDebtCancellationShares_80" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAStatementLineItems" xlink:to="loc_VSTACommonStockIssuedUponExerciseOfOptionsFrom1999StockIncentivePlanAndWarrantsForDebtCancellationShares_80" xlink:type="arc" order="22" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_CommonStockIssuedUponExerciseOfOptionsFrom1999StockIncentivePlanAndWarrantsForNotesReceivableAmount" xlink:label="loc_VSTACommonStockIssuedUponExerciseOfOptionsFrom1999StockIncentivePlanAndWarrantsForNotesReceivableAmount_80" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAStatementLineItems" xlink:to="loc_VSTACommonStockIssuedUponExerciseOfOptionsFrom1999StockIncentivePlanAndWarrantsForNotesReceivableAmount_80" xlink:type="arc" order="23" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_CommonStockIssuedUponExerciseOfOptionsFrom1999StockIncentivePlanAndWarrantsForNotesReceivableShares" xlink:label="loc_VSTACommonStockIssuedUponExerciseOfOptionsFrom1999StockIncentivePlanAndWarrantsForNotesReceivableShares_80" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAStatementLineItems" xlink:to="loc_VSTACommonStockIssuedUponExerciseOfOptionsFrom1999StockIncentivePlanAndWarrantsForNotesReceivableShares_80" xlink:type="arc" order="24" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_SharebasedCompensationExpense" xlink:label="loc_VSTASharebasedCompensationExpense_80" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAStatementLineItems" xlink:to="loc_VSTASharebasedCompensationExpense_80" xlink:type="arc" order="25" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_ForgivenessOfAccruedCompensationAndAccruedInterestPayableToOfficers" xlink:label="loc_VSTAForgivenessOfAccruedCompensationAndAccruedInterestPayableToOfficers_80" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAStatementLineItems" xlink:to="loc_VSTAForgivenessOfAccruedCompensationAndAccruedInterestPayableToOfficers_80" xlink:type="arc" order="26" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_CommonStockIssuedUponSettlementOfEmploymentContractAmount" xlink:label="loc_VSTACommonStockIssuedUponSettlementOfEmploymentContractAmount_80" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAStatementLineItems" xlink:to="loc_VSTACommonStockIssuedUponSettlementOfEmploymentContractAmount_80" xlink:type="arc" order="27" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_CommonStockIssuedUponSettlementOfEmploymentContractShares" xlink:label="loc_VSTACommonStockIssuedUponSettlementOfEmploymentContractShares_80" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAStatementLineItems" xlink:to="loc_VSTACommonStockIssuedUponSettlementOfEmploymentContractShares_80" xlink:type="arc" order="28" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_ProceedsAllocatedToWarrantsIssuedInConnectionWithPlatinumNotes" xlink:label="loc_VSTAProceedsAllocatedToWarrantsIssuedInConnectionWithPlatinumNotes_80" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAStatementLineItems" xlink:to="loc_VSTAProceedsAllocatedToWarrantsIssuedInConnectionWithPlatinumNotes_80" xlink:type="arc" order="29" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_AccruedInterestOnNotesReceivable" xlink:label="loc_VSTAAccruedInterestOnNotesReceivable_80" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAStatementLineItems" xlink:to="loc_VSTAAccruedInterestOnNotesReceivable_80" xlink:type="arc" order="30" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_CommonStockIssuedUponExerciseOfOptionsFrom2008StockIncentivePlanAndScientificAdvisoryPlanAmount" xlink:label="loc_VSTACommonStockIssuedUponExerciseOfOptionsFrom2008StockIncentivePlanAndScientificAdvisoryPlanAmount_80" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAStatementLineItems" xlink:to="loc_VSTACommonStockIssuedUponExerciseOfOptionsFrom2008StockIncentivePlanAndScientificAdvisoryPlanAmount_80" xlink:type="arc" order="31" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_CommonStockIssuedUponExerciseOfOptionsFrom2008StockIncentivePlanAndScientificAdvisoryPlanShares" xlink:label="loc_VSTACommonStockIssuedUponExerciseOfOptionsFrom2008StockIncentivePlanAndScientificAdvisoryPlanShares_80" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAStatementLineItems" xlink:to="loc_VSTACommonStockIssuedUponExerciseOfOptionsFrom2008StockIncentivePlanAndScientificAdvisoryPlanShares_80" xlink:type="arc" order="32" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_ProceedsAllocatedToWarrantsIssuedInConnectionWithPlatinumNotesAndIncrementalFairValueOfWarrantModification" xlink:label="loc_VSTAProceedsAllocatedToWarrantsIssuedInConnectionWithPlatinumNotesAndIncrementalFairValueOfWarrantModification_80" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAStatementLineItems" xlink:to="loc_VSTAProceedsAllocatedToWarrantsIssuedInConnectionWithPlatinumNotesAndIncrementalFairValueOfWarrantModification_80" xlink:type="arc" order="33" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_EffectOfReverseStockSplit" xlink:label="loc_VSTAEffectOfReverseStockSplit_80" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAStatementLineItems" xlink:to="loc_VSTAEffectOfReverseStockSplit_80" xlink:type="arc" order="34" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_CumulativeEffectOfAdoptingNewAccountingStandard" xlink:label="loc_VSTACumulativeEffectOfAdoptingNewAccountingStandard_80" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAStatementLineItems" xlink:to="loc_VSTACumulativeEffectOfAdoptingNewAccountingStandard_80" xlink:type="arc" order="35" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_CommonStockIssuedUponExerciseOfWarrantAmount" xlink:label="loc_VSTACommonStockIssuedUponExerciseOfWarrantAmount_80" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAStatementLineItems" xlink:to="loc_VSTACommonStockIssuedUponExerciseOfWarrantAmount_80" xlink:type="arc" order="36" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_CommonStockIssuedUponExerciseOfWarrantShares" xlink:label="loc_VSTACommonStockIssuedUponExerciseOfWarrantShares_80" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAStatementLineItems" xlink:to="loc_VSTACommonStockIssuedUponExerciseOfWarrantShares_80" xlink:type="arc" order="37" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_CommonStockIssuedForCancellationOfAccountsPayableAndAccruedInterestAmount" xlink:label="loc_VSTACommonStockIssuedForCancellationOfAccountsPayableAndAccruedInterestAmount_80" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAStatementLineItems" xlink:to="loc_VSTACommonStockIssuedForCancellationOfAccountsPayableAndAccruedInterestAmount_80" xlink:type="arc" order="38" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_CommonStockIssuedForCancellationOfAccountsPayableAndAccruedInterestShares" xlink:label="loc_VSTACommonStockIssuedForCancellationOfAccountsPayableAndAccruedInterestShares_80" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAStatementLineItems" xlink:to="loc_VSTACommonStockIssuedForCancellationOfAccountsPayableAndAccruedInterestShares_80" xlink:type="arc" order="39" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_IncrementalFairValueOfNoteConversionOptionsFromDebtModification" xlink:label="loc_VSTAIncrementalFairValueOfNoteConversionOptionsFromDebtModification_80" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAStatementLineItems" xlink:to="loc_VSTAIncrementalFairValueOfNoteConversionOptionsFromDebtModification_80" xlink:type="arc" order="40" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_CommonStockIssuedForServicesAmount" xlink:label="loc_VSTACommonStockIssuedForServicesAmount_80" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAStatementLineItems" xlink:to="loc_VSTACommonStockIssuedForServicesAmount_80" xlink:type="arc" order="41" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_CommonStockIssuedForServicesShares" xlink:label="loc_VSTACommonStockIssuedForServicesShares_80" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAStatementLineItems" xlink:to="loc_VSTACommonStockIssuedForServicesShares_80" xlink:type="arc" order="42" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_FairValueOfWarrantsIssuedForServicesAndIncrementalFairValueOfWarrantModification" xlink:label="loc_VSTAFairValueOfWarrantsIssuedForServicesAndIncrementalFairValueOfWarrantModification_80" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAStatementLineItems" xlink:to="loc_VSTAFairValueOfWarrantsIssuedForServicesAndIncrementalFairValueOfWarrantModification_80" xlink:type="arc" order="43" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_FairValueOfWarrantsIssuedInConnectionWith7.5Notes" xlink:label="loc_VSTAFairValueOfWarrantsIssuedInConnectionWith7.5Notes_80" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAStatementLineItems" xlink:to="loc_VSTAFairValueOfWarrantsIssuedInConnectionWith7.5Notes_80" xlink:type="arc" order="44" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_FairValueOfWarrantsIssuedInConnectionWithAugust2010ShorttermNotes" xlink:label="loc_VSTAFairValueOfWarrantsIssuedInConnectionWithAugust2010ShorttermNotes_80" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAStatementLineItems" xlink:to="loc_VSTAFairValueOfWarrantsIssuedInConnectionWithAugust2010ShorttermNotes_80" xlink:type="arc" order="45" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_ReclassificationOfWarrantLiabilityToEquity" xlink:label="loc_VSTAReclassificationOfWarrantLiabilityToEquity_80" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAStatementLineItems" xlink:to="loc_VSTAReclassificationOfWarrantLiabilityToEquity_80" xlink:type="arc" order="46" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_IncrementalValueOfPlatinumNoteModification" xlink:label="loc_VSTAIncrementalValueOfPlatinumNoteModification_80" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAStatementLineItems" xlink:to="loc_VSTAIncrementalValueOfPlatinumNoteModification_80" xlink:type="arc" order="47" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_IncrementalValueOfMorrisonFoersterWarrantModification" xlink:label="loc_VSTAIncrementalValueOfMorrisonFoersterWarrantModification_80" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAStatementLineItems" xlink:to="loc_VSTAIncrementalValueOfMorrisonFoersterWarrantModification_80" xlink:type="arc" order="48" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_StockIssuedInMay2011PrivatePlacementNetOf202000PlacementFeesAmount" xlink:label="loc_VSTAStockIssuedInMay2011PrivatePlacementNetOf202000PlacementFeesAmount_80" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAStatementLineItems" xlink:to="loc_VSTAStockIssuedInMay2011PrivatePlacementNetOf202000PlacementFeesAmount_80" xlink:type="arc" order="49" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_StockIssuedInMay2011PrivatePlacementNetOf202000PlacementFeesShares" xlink:label="loc_VSTAStockIssuedInMay2011PrivatePlacementNetOf202000PlacementFeesShares_80" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAStatementLineItems" xlink:to="loc_VSTAStockIssuedInMay2011PrivatePlacementNetOf202000PlacementFeesShares_80" xlink:type="arc" order="50" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_PaymentsOnNoteReceivableForSaleOfStock" xlink:label="loc_VSTAPaymentsOnNoteReceivableForSaleOfStock_80" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAStatementLineItems" xlink:to="loc_VSTAPaymentsOnNoteReceivableForSaleOfStock_80" xlink:type="arc" order="51" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_StockIssuedUponConversionOfConvertiblePromissoryNotesAmount" xlink:label="loc_VSTAStockIssuedUponConversionOfConvertiblePromissoryNotesAmount_80" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAStatementLineItems" xlink:to="loc_VSTAStockIssuedUponConversionOfConvertiblePromissoryNotesAmount_80" xlink:type="arc" order="52" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_StockIssuedUponConversionOfConvertiblePromissoryNotesShares" xlink:label="loc_VSTAStockIssuedUponConversionOfConvertiblePromissoryNotesShares_80" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAStatementLineItems" xlink:to="loc_VSTAStockIssuedUponConversionOfConvertiblePromissoryNotesShares_80" xlink:type="arc" order="53" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_StockIssuedUponConversionOfAllSeriesOfPreferredStockAmount" xlink:label="loc_VSTAStockIssuedUponConversionOfAllSeriesOfPreferredStockAmount_80" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAStatementLineItems" xlink:to="loc_VSTAStockIssuedUponConversionOfAllSeriesOfPreferredStockAmount_80" xlink:type="arc" order="54" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_StockIssuedUponConversionOfAllSeriesOfPreferredStockShares" xlink:label="loc_VSTAStockIssuedUponConversionOfAllSeriesOfPreferredStockShares_80" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAStatementLineItems" xlink:to="loc_VSTAStockIssuedUponConversionOfAllSeriesOfPreferredStockShares_80" xlink:type="arc" order="55" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_FairValueOfStockIssuedForServicesPriorToMergerAmount" xlink:label="loc_VSTAFairValueOfStockIssuedForServicesPriorToMergerAmount_80" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAStatementLineItems" xlink:to="loc_VSTAFairValueOfStockIssuedForServicesPriorToMergerAmount_80" xlink:type="arc" order="56" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_FairValueOfStockIssuedForServicesPriorToMergerShares" xlink:label="loc_VSTAFairValueOfStockIssuedForServicesPriorToMergerShares_80" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAStatementLineItems" xlink:to="loc_VSTAFairValueOfStockIssuedForServicesPriorToMergerShares_80" xlink:type="arc" order="57" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_ForgivenessOfNotesAtTheMergerAmount" xlink:label="loc_VSTAForgivenessOfNotesAtTheMergerAmount_80" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAStatementLineItems" xlink:to="loc_VSTAForgivenessOfNotesAtTheMergerAmount_80" xlink:type="arc" order="58" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_ForgivenessOfNotesAtTheMergerShares" xlink:label="loc_VSTAForgivenessOfNotesAtTheMergerShares_80" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAStatementLineItems" xlink:to="loc_VSTAForgivenessOfNotesAtTheMergerShares_80" xlink:type="arc" order="59" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_StockIssuedUponExerciseOfModifiedWarrantsIncludesPlatinumExercisesAmount" xlink:label="loc_VSTAStockIssuedUponExerciseOfModifiedWarrantsIncludesPlatinumExercisesAmount_80" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAStatementLineItems" xlink:to="loc_VSTAStockIssuedUponExerciseOfModifiedWarrantsIncludesPlatinumExercisesAmount_80" xlink:type="arc" order="60" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_StockIssuedUponExerciseOfModifiedWarrantsIncludesPlatinumExercisesShares" xlink:label="loc_VSTAStockIssuedUponExerciseOfModifiedWarrantsIncludesPlatinumExercisesShares_80" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAStatementLineItems" xlink:to="loc_VSTAStockIssuedUponExerciseOfModifiedWarrantsIncludesPlatinumExercisesShares_80" xlink:type="arc" order="61" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_IncrementalValueOfWarrantModificationsIncludingModificationOfPlatinumWarrants" xlink:label="loc_VSTAIncrementalValueOfWarrantModificationsIncludingModificationOfPlatinumWarrants_80" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAStatementLineItems" xlink:to="loc_VSTAIncrementalValueOfWarrantModificationsIncludingModificationOfPlatinumWarrants_80" xlink:type="arc" order="62" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_FairValueOfBonusWarrantsUnderDiscountedWarrantExerciseProgram" xlink:label="loc_VSTAFairValueOfBonusWarrantsUnderDiscountedWarrantExerciseProgram_80" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAStatementLineItems" xlink:to="loc_VSTAFairValueOfBonusWarrantsUnderDiscountedWarrantExerciseProgram_80" xlink:type="arc" order="63" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_StockIssuedInFall2011FollowonOfferingAmount" xlink:label="loc_VSTAStockIssuedInFall2011FollowonOfferingAmount_80" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAStatementLineItems" xlink:to="loc_VSTAStockIssuedInFall2011FollowonOfferingAmount_80" xlink:type="arc" order="64" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_StockIssuedInFall2011FollowonOfferingShares" xlink:label="loc_VSTAStockIssuedInFall2011FollowonOfferingShares_80" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAStatementLineItems" xlink:to="loc_VSTAStockIssuedInFall2011FollowonOfferingShares_80" xlink:type="arc" order="65" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_StockIssuedUponExerciseOfOptionsFrom1999StockIncentivePlanAmount" xlink:label="loc_VSTAStockIssuedUponExerciseOfOptionsFrom1999StockIncentivePlanAmount_80" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAStatementLineItems" xlink:to="loc_VSTAStockIssuedUponExerciseOfOptionsFrom1999StockIncentivePlanAmount_80" xlink:type="arc" order="66" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_StockIssuedUponExerciseOfOptionsFrom1999StockIncentivePlanShares" xlink:label="loc_VSTAStockIssuedUponExerciseOfOptionsFrom1999StockIncentivePlanShares_80" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAStatementLineItems" xlink:to="loc_VSTAStockIssuedUponExerciseOfOptionsFrom1999StockIncentivePlanShares_80" xlink:type="arc" order="67" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_FairValueOfStockIssuedForServicesFollowingMergerAmount" xlink:label="loc_VSTAFairValueOfStockIssuedForServicesFollowingMergerAmount_80" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAStatementLineItems" xlink:to="loc_VSTAFairValueOfStockIssuedForServicesFollowingMergerAmount_80" xlink:type="arc" order="68" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_FairValueOfStockIssuedForServicesFollowingMergerShares" xlink:label="loc_VSTAFairValueOfStockIssuedForServicesFollowingMergerShares_80" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAStatementLineItems" xlink:to="loc_VSTAFairValueOfStockIssuedForServicesFollowingMergerShares_80" xlink:type="arc" order="69" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_PlacementFeesOn12ConvertibleNotes" xlink:label="loc_VSTAPlacementFeesOn12ConvertibleNotes_80" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAStatementLineItems" xlink:to="loc_VSTAPlacementFeesOn12ConvertibleNotes_80" xlink:type="arc" order="70" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_ProceedsAllocatedToWarrantsIssuedAndBeneficialConversionFeatureInConnectionWith12ConvertibleNotes" xlink:label="loc_VSTAProceedsAllocatedToWarrantsIssuedAndBeneficialConversionFeatureInConnectionWith12ConvertibleNotes_80" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAStatementLineItems" xlink:to="loc_VSTAProceedsAllocatedToWarrantsIssuedAndBeneficialConversionFeatureInConnectionWith12ConvertibleNotes_80" xlink:type="arc" order="71" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_StockIssuedInConnectionWithNoteTermExtensionAmount" xlink:label="loc_VSTAStockIssuedInConnectionWithNoteTermExtensionAmount_80" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAStatementLineItems" xlink:to="loc_VSTAStockIssuedInConnectionWithNoteTermExtensionAmount_80" xlink:type="arc" order="72" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_StockIssuedInConnectionWithNoteTermExtensionShares" xlink:label="loc_VSTAStockIssuedInConnectionWithNoteTermExtensionShares_80" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAStatementLineItems" xlink:to="loc_VSTAStockIssuedInConnectionWithNoteTermExtensionShares_80" xlink:type="arc" order="73" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_StockIssuedUponConversionOfPlatinumNoteToEquityNetOfPlatinumWarrantExerciseReflectedAboveAmount" xlink:label="loc_VSTAStockIssuedUponConversionOfPlatinumNoteToEquityNetOfPlatinumWarrantExerciseReflectedAboveAmount_80" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAStatementLineItems" xlink:to="loc_VSTAStockIssuedUponConversionOfPlatinumNoteToEquityNetOfPlatinumWarrantExerciseReflectedAboveAmount_80" xlink:type="arc" order="74" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_StockIssuedUponConversionOfPlatinumNoteToEquityNetOfPlatinumWarrantExerciseReflectedAboveShares" xlink:label="loc_VSTAStockIssuedUponConversionOfPlatinumNoteToEquityNetOfPlatinumWarrantExerciseReflectedAboveShares_80" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAStatementLineItems" xlink:to="loc_VSTAStockIssuedUponConversionOfPlatinumNoteToEquityNetOfPlatinumWarrantExerciseReflectedAboveShares_80" xlink:type="arc" order="75" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_CommonStockExchangedForSeriesPreferredUnderAgreementsWithPlatinumCommonStockExchangeAgreementAmount" xlink:label="loc_VSTACommonStockExchangedForSeriesPreferredUnderAgreementsWithPlatinumCommonStockExchangeAgreementAmount_80" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAStatementLineItems" xlink:to="loc_VSTACommonStockExchangedForSeriesPreferredUnderAgreementsWithPlatinumCommonStockExchangeAgreementAmount_80" xlink:type="arc" order="76" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_CommonStockExchangedForSeriesPreferredUnderAgreementsWithPlatinumCommonStockExchangeAgreementShares" xlink:label="loc_VSTACommonStockExchangedForSeriesPreferredUnderAgreementsWithPlatinumCommonStockExchangeAgreementShares_80" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAStatementLineItems" xlink:to="loc_VSTACommonStockExchangedForSeriesPreferredUnderAgreementsWithPlatinumCommonStockExchangeAgreementShares_80" xlink:type="arc" order="77" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_CommonStockExchangedForSeriesPreferredUnderAgreementsWithPlatinumNoteAndWarrantExchangeAgreementAmount" xlink:label="loc_VSTACommonStockExchangedForSeriesPreferredUnderAgreementsWithPlatinumNoteAndWarrantExchangeAgreementAmount_80" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAStatementLineItems" xlink:to="loc_VSTACommonStockExchangedForSeriesPreferredUnderAgreementsWithPlatinumNoteAndWarrantExchangeAgreementAmount_80" xlink:type="arc" order="78" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_CommonStockExchangedForSeriesPreferredUnderAgreementsWithPlatinumNoteAndWarrantExchangeAgreementShares" xlink:label="loc_VSTACommonStockExchangedForSeriesPreferredUnderAgreementsWithPlatinumNoteAndWarrantExchangeAgreementShares_80" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAStatementLineItems" xlink:to="loc_VSTACommonStockExchangedForSeriesPreferredUnderAgreementsWithPlatinumNoteAndWarrantExchangeAgreementShares_80" xlink:type="arc" order="79" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_FairValueOfWarrantsIssuedUponExerciseOfModifiedWarrants" xlink:label="loc_VSTAFairValueOfWarrantsIssuedUponExerciseOfModifiedWarrants_80" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAStatementLineItems" xlink:to="loc_VSTAFairValueOfWarrantsIssuedUponExerciseOfModifiedWarrants_80" xlink:type="arc" order="80" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_FairValueOfSharesIssuedInSettlementOfAccountsPayable" xlink:label="loc_VSTAFairValueOfSharesIssuedInSettlementOfAccountsPayable_80" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAStatementLineItems" xlink:to="loc_VSTAFairValueOfSharesIssuedInSettlementOfAccountsPayable_80" xlink:type="arc" order="81" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_FairValueOfSharesIssuedInSettlementOfAccountsPayableShares" xlink:label="loc_VSTAFairValueOfSharesIssuedInSettlementOfAccountsPayableShares_80" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAStatementLineItems" xlink:to="loc_VSTAFairValueOfSharesIssuedInSettlementOfAccountsPayableShares_80" xlink:type="arc" order="82" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_ModificationOfNoteReceivableFromSaleOfStock" xlink:label="loc_VSTAModificationOfNoteReceivableFromSaleOfStock_80" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAStatementLineItems" xlink:to="loc_VSTAModificationOfNoteReceivableFromSaleOfStock_80" xlink:type="arc" order="83" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_FairValueOfWarrantIssuedToCatoHoldingCompanyInConnectionWithNotePayableRestructure" xlink:label="loc_VSTAFairValueOfWarrantIssuedToCatoHoldingCompanyInConnectionWithNotePayableRestructure_80" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAStatementLineItems" xlink:to="loc_VSTAFairValueOfWarrantIssuedToCatoHoldingCompanyInConnectionWithNotePayableRestructure_80" xlink:type="arc" order="84" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_FairValueOfWarrantIssuedInConnectionWithAccountsPayableRestructure" xlink:label="loc_VSTAFairValueOfWarrantIssuedInConnectionWithAccountsPayableRestructure_80" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAStatementLineItems" xlink:to="loc_VSTAFairValueOfWarrantIssuedInConnectionWithAccountsPayableRestructure_80" xlink:type="arc" order="85" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_FairValueOfWarrantIssued2InConnectionWithAccountsPayableRestructure" xlink:label="loc_VSTAFairValueOfWarrantIssued2InConnectionWithAccountsPayableRestructure_80" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAStatementLineItems" xlink:to="loc_VSTAFairValueOfWarrantIssued2InConnectionWithAccountsPayableRestructure_80" xlink:type="arc" order="86" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_FairValueOfWarrantsIssuedInConnectionWithAccruedInterestOnUnderlyingNotes" xlink:label="loc_VSTAFairValueOfWarrantsIssuedInConnectionWithAccruedInterestOnUnderlyingNotes_80" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAStatementLineItems" xlink:to="loc_VSTAFairValueOfWarrantsIssuedInConnectionWithAccruedInterestOnUnderlyingNotes_80" xlink:type="arc" order="87" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_SaleOfUnitsInWinter2012PrivatePlacementNetAmount" xlink:label="loc_VSTASaleOfUnitsInWinter2012PrivatePlacementNetAmount_80" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAStatementLineItems" xlink:to="loc_VSTASaleOfUnitsInWinter2012PrivatePlacementNetAmount_80" xlink:type="arc" order="88" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_SaleOfUnitsInWinter2012PrivatePlacementNetShares" xlink:label="loc_VSTASaleOfUnitsInWinter2012PrivatePlacementNetShares_80" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAStatementLineItems" xlink:to="loc_VSTASaleOfUnitsInWinter2012PrivatePlacementNetShares_80" xlink:type="arc" order="89" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_ExchangeOfFebruary2012ConvertibleNotesAmount" xlink:label="loc_VSTAExchangeOfFebruary2012ConvertibleNotesAmount_80" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAStatementLineItems" xlink:to="loc_VSTAExchangeOfFebruary2012ConvertibleNotesAmount_80" xlink:type="arc" order="90" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_ExchangeOfFebruary2012ConvertibleNotesShares" xlink:label="loc_VSTAExchangeOfFebruary2012ConvertibleNotesShares_80" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAStatementLineItems" xlink:to="loc_VSTAExchangeOfFebruary2012ConvertibleNotesShares_80" xlink:type="arc" order="91" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_FairValueOfWarrantsIssuedToBankerInConnectionWithExchangeOfFebruary2012ConvertibleNotes" xlink:label="loc_VSTAFairValueOfWarrantsIssuedToBankerInConnectionWithExchangeOfFebruary2012ConvertibleNotes_80" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAStatementLineItems" xlink:to="loc_VSTAFairValueOfWarrantsIssuedToBankerInConnectionWithExchangeOfFebruary2012ConvertibleNotes_80" xlink:type="arc" order="92" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_PremiumOfFairValueOverFaceValueOfExchangeNoteIssuedToPlatinum" xlink:label="loc_VSTAPremiumOfFairValueOverFaceValueOfExchangeNoteIssuedToPlatinum_80" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAStatementLineItems" xlink:to="loc_VSTAPremiumOfFairValueOverFaceValueOfExchangeNoteIssuedToPlatinum_80" xlink:type="arc" order="93" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_IncreaseDecreaseInDerivativeLiabilities" xlink:label="loc_VSTAIncreaseDecreaseInDerivativeLiabilities_80" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAStatementLineItems" xlink:to="loc_VSTAIncreaseDecreaseInDerivativeLiabilities_80" xlink:type="arc" order="94" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_ProceedsAllocatedToBeneficialConversionFeatureOfInvestmentNotesIssuedToPlatinumInOctober2012February2013AndMarch2013" xlink:label="loc_VSTAProceedsAllocatedToBeneficialConversionFeatureOfInvestmentNotesIssuedToPlatinumInOctober2012February2013AndMarch2013_80" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAStatementLineItems" xlink:to="loc_VSTAProceedsAllocatedToBeneficialConversionFeatureOfInvestmentNotesIssuedToPlatinumInOctober2012February2013AndMarch2013_80" xlink:type="arc" order="95" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_IncrementalFairValueOfWarrantModificationsInFeburary2013" xlink:label="loc_VSTAIncrementalFairValueOfWarrantModificationsInFeburary2013_80" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAStatementLineItems" xlink:to="loc_VSTAIncrementalFairValueOfWarrantModificationsInFeburary2013_80" xlink:type="arc" order="96" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_NetIncomeLoss" xlink:label="loc_VSTANetIncomeLoss_80" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAStatementLineItems" xlink:to="loc_VSTANetIncomeLoss_80" xlink:type="arc" order="98" />
    </link:definitionLink>
    <link:definitionLink xlink:type="extended" xlink:role="http://vistagen.com/role/DescriptionOfBusiness" xlink:title="0008 - Disclosure - Description of Business" />
    <link:definitionLink xlink:type="extended" xlink:role="http://vistagen.com/role/BasisOfPresentationAndGoingConcern" xlink:title="0009 - Disclosure - Basis of Presentation and Going Concern" />
    <link:definitionLink xlink:type="extended" xlink:role="http://vistagen.com/role/SummaryOfSignificantAccountingPolicies" xlink:title="0010 - Disclosure - Summary of Significant Accounting Policies" />
    <link:definitionLink xlink:type="extended" xlink:role="http://vistagen.com/role/FairValueMeasurements" xlink:title="0011 - Disclosure - Fair Value Measurements" />
    <link:definitionLink xlink:type="extended" xlink:role="http://vistagen.com/role/PropertyAndEquipment" xlink:title="0012 - Disclosure - Property and Equipment" />
    <link:definitionLink xlink:type="extended" xlink:role="http://vistagen.com/role/Av-101Acquisition" xlink:title="0013 - Disclosure - AV-101 Acquisition" />
    <link:definitionLink xlink:type="extended" xlink:role="http://vistagen.com/role/AccruedExpenses" xlink:title="0014 - Disclosure - Accrued Expenses" />
    <link:definitionLink xlink:type="extended" xlink:role="http://vistagen.com/role/ConvertiblePromissoryNotesAndOtherNotesPayable" xlink:title="0015 - Disclosure - Convertible Promissory Notes and Other Notes Payable" />
    <link:definitionLink xlink:type="extended" xlink:role="http://vistagen.com/role/CapitalStock" xlink:title="0016 - Disclosure - Capital Stock" />
    <link:definitionLink xlink:type="extended" xlink:role="http://vistagen.com/role/ResearchAndDevelopmentExpenses" xlink:title="0017 - Disclosure - Research and Development Expenses" />
    <link:definitionLink xlink:type="extended" xlink:role="http://vistagen.com/role/IncomeTaxes" xlink:title="0018 - Disclosure - Income Taxes" />
    <link:definitionLink xlink:type="extended" xlink:role="http://vistagen.com/role/LicensingAndCollaborativeAgreements" xlink:title="0019 - Disclosure - Licensing and Collaborative Agreements" />
    <link:definitionLink xlink:type="extended" xlink:role="http://vistagen.com/role/StockOptionPlansAnd401KPlan" xlink:title="0020 - Disclosure - Stock Option Plans and 401(k) Plan" />
    <link:definitionLink xlink:type="extended" xlink:role="http://vistagen.com/role/RelatedPartyTransactions" xlink:title="0021 - Disclosure - Related Party Transactions" />
    <link:definitionLink xlink:type="extended" xlink:role="http://vistagen.com/role/CommitmentsContingenciesGuaranteesAndIndemnifications" xlink:title="0022 - Disclosure - Commitments, Contingencies, Guarantees and Indemnifications" />
    <link:definitionLink xlink:type="extended" xlink:role="http://vistagen.com/role/SubsequentEvents" xlink:title="0023 - Disclosure - Subsequent Events" />
    <link:definitionLink xlink:type="extended" xlink:role="http://vistagen.com/role/SupplementalFinancialInformation" xlink:title="0024 - Disclosure - Supplemental Financial Information" />
    <link:definitionLink xlink:type="extended" xlink:role="http://vistagen.com/role/SummaryOfSignificantAccountingPoliciesPolicies" xlink:title="0025 - Disclosure - Summary of Significant Accounting Policies (Policies)" />
    <link:definitionLink xlink:type="extended" xlink:role="http://vistagen.com/role/SummaryOfSignificantAccountingPoliciesTables" xlink:title="0026 - Disclosure - Summary of Significant Accounting Policies (Tables)" />
    <link:definitionLink xlink:type="extended" xlink:role="http://vistagen.com/role/FairValueMeasurementsTables" xlink:title="0027 - Disclosure - Fair Value Measurements (Tables)" />
    <link:definitionLink xlink:type="extended" xlink:role="http://vistagen.com/role/PropertyAndEquipmentTables" xlink:title="0028 - Disclosure - Property and Equipment (Tables)" />
    <link:definitionLink xlink:type="extended" xlink:role="http://vistagen.com/role/AccruedExpensesTables" xlink:title="0029 - Disclosure - Accrued Expenses (Tables)" />
    <link:definitionLink xlink:type="extended" xlink:role="http://vistagen.com/role/ConvertiblePromissoryNotesAndOtherNotesPayableTables" xlink:title="0030 - Disclosure - Convertible Promissory Notes and Other Notes Payable (Tables)" />
    <link:definitionLink xlink:type="extended" xlink:role="http://vistagen.com/role/CapitalStockTables" xlink:title="0031 - Disclosure - Capital Stock (Tables)" />
    <link:definitionLink xlink:type="extended" xlink:role="http://vistagen.com/role/IncomeTaxesTables" xlink:title="0032 - Disclosure - Income Taxes (Tables)" />
    <link:definitionLink xlink:type="extended" xlink:role="http://vistagen.com/role/StockOptionPlansAnd401KPlanTables" xlink:title="0033 - Disclosure - Stock Option Plans and 401(k) Plan (Tables)" />
    <link:definitionLink xlink:type="extended" xlink:role="http://vistagen.com/role/CommitmentsContingenciesGuaranteesAndIndemnificationsTables" xlink:title="0034 - Disclosure - Commitments, Contingencies, Guarantees and Indemnifications (Tables)" />
    <link:definitionLink xlink:type="extended" xlink:role="http://vistagen.com/role/SubsequentEventsTables" xlink:title="0035 - Disclosure - Subsequent Events (Tables)" />
    <link:definitionLink xlink:type="extended" xlink:role="http://vistagen.com/role/SupplementalFinancialInformationTables" xlink:title="0036 - Disclosure - Supplemental Financial Information (Tables)" />
    <link:definitionLink xlink:type="extended" xlink:role="http://vistagen.com/role/DescriptionOfBusinessDetailsTextuals" xlink:title="0037 - Disclosure - Description of Business (Details Textuals)" />
    <link:definitionLink xlink:type="extended" xlink:role="http://vistagen.com/role/BasisOfPresentationAndGoingConcernDetailsTextuals" xlink:title="0038 - Disclosure - Basis of Presentation and Going Concern (Details Textuals)" />
    <link:definitionLink xlink:type="extended" xlink:role="http://vistagen.com/role/SummaryOfSignificantAccountingPoliciesDetails" xlink:title="0039 - Disclosure - Summary of Significant Accounting Policies (Details)" />
    <link:definitionLink xlink:type="extended" xlink:role="http://vistagen.com/role/FairValueMeasurementsDetails" xlink:title="0040 - Disclosure - Fair Value Measurements (Details)">
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_StatementLineItems" xlink:label="loc_VSTAStatementLineItems" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_StatementTable" xlink:label="loc_VSTAStatementTable" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xbrldt:contextElement="segment" xlink:from="loc_VSTAStatementLineItems" xlink:to="loc_VSTAStatementTable" xlink:type="arc" order="10" xbrldt:closed="true" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_FairValueByFairValueHierarchyLevelAxis" xlink:label="loc_VSTAFairValueByFairValueHierarchyLevelAxis" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_VSTAStatementTable" xlink:to="loc_VSTAFairValueByFairValueHierarchyLevelAxis" xlink:type="arc" order="1" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain" xlink:label="loc_VSTAFairValueMeasurementsFairValueHierarchyDomain" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_VSTAFairValueByFairValueHierarchyLevelAxis" xlink:to="loc_VSTAFairValueMeasurementsFairValueHierarchyDomain" xlink:type="arc" order="20" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain" xlink:label="loc_VSTAFairValueMeasurementsFairValueHierarchyDomain_10" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xbrldt:contextElement="segment" xlink:from="loc_VSTAFairValueByFairValueHierarchyLevelAxis" xlink:to="loc_VSTAFairValueMeasurementsFairValueHierarchyDomain_10" xlink:type="arc" order="30" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_FairValueInputsLevel1Member" xlink:label="loc_VSTAFairValueInputsLevel1Member_0" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAFairValueMeasurementsFairValueHierarchyDomain" xlink:to="loc_VSTAFairValueInputsLevel1Member_0" xlink:type="arc" order="1" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_FairValueInputsLevel2Member" xlink:label="loc_VSTAFairValueInputsLevel2Member_20" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAFairValueMeasurementsFairValueHierarchyDomain" xlink:to="loc_VSTAFairValueInputsLevel2Member_20" xlink:type="arc" order="21" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_FairValueInputsLevel3Member" xlink:label="loc_VSTAFairValueInputsLevel3Member_40" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAFairValueMeasurementsFairValueHierarchyDomain" xlink:to="loc_VSTAFairValueInputsLevel3Member_40" xlink:type="arc" order="41" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_LiabilitiesFairValueDisclosureAbstract" xlink:label="loc_VSTALiabilitiesFairValueDisclosureAbstract_90" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAStatementLineItems" xlink:to="loc_VSTALiabilitiesFairValueDisclosureAbstract_90" xlink:type="arc" order="0" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationsRecurringBasisLiabilityValue" xlink:label="loc_VSTAFairValueMeasurementWithUnobservableInputsReconciliationsRecurringBasisLiabilityValue_90" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTALiabilitiesFairValueDisclosureAbstract_90" xlink:to="loc_VSTAFairValueMeasurementWithUnobservableInputsReconciliationsRecurringBasisLiabilityValue_90" xlink:type="arc" order="1" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_FairValueMeasurementWithUnobservableInputsReconciliationsRecurringBasisLiabilityValue1" xlink:label="loc_VSTAFairValueMeasurementWithUnobservableInputsReconciliationsRecurringBasisLiabilityValue1_90" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTALiabilitiesFairValueDisclosureAbstract_90" xlink:to="loc_VSTAFairValueMeasurementWithUnobservableInputsReconciliationsRecurringBasisLiabilityValue1_90" xlink:type="arc" order="2" />
    </link:definitionLink>
    <link:definitionLink xlink:type="extended" xlink:role="http://vistagen.com/role/FairValueMeasurementsDetailsTextuals" xlink:title="0041 - Disclosure - Fair Value Measurements (Details Textuals)" />
    <link:definitionLink xlink:type="extended" xlink:role="http://vistagen.com/role/PropertyAndEquipmentDetails" xlink:title="0042 - Disclosure - Property and Equipment (Details)" />
    <link:definitionLink xlink:type="extended" xlink:role="http://vistagen.com/role/Av-101AcquisitionDetailsTextuals" xlink:title="0043 - Disclosure - AV-101 Acquisition (Details Textuals)" />
    <link:definitionLink xlink:type="extended" xlink:role="http://vistagen.com/role/AccruedExpensesDetails" xlink:title="0044 - Disclosure - Accrued Expenses (Details)" />
    <link:definitionLink xlink:type="extended" xlink:role="http://vistagen.com/role/ConvertiblePromissoryNotesAndOtherNotesPayableDetails" xlink:title="0045 - Disclosure - 7. Convertible Promissory Notes and Other Notes Payable (Details)">
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_StatementLineItems" xlink:label="loc_VSTAStatementLineItems" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_StatementTable" xlink:label="loc_VSTAStatementTable" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xbrldt:contextElement="segment" xlink:from="loc_VSTAStatementLineItems" xlink:to="loc_VSTAStatementTable" xlink:type="arc" order="10" xbrldt:closed="true" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_RelatedPartyTransactionsByRelatedPartyAxis" xlink:label="loc_VSTARelatedPartyTransactionsByRelatedPartyAxis" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_VSTAStatementTable" xlink:to="loc_VSTARelatedPartyTransactionsByRelatedPartyAxis" xlink:type="arc" order="1" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_RelatedPartyDomain" xlink:label="loc_VSTARelatedPartyDomain" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_VSTARelatedPartyTransactionsByRelatedPartyAxis" xlink:to="loc_VSTARelatedPartyDomain" xlink:type="arc" order="20" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_RelatedPartyDomain" xlink:label="loc_VSTARelatedPartyDomain_10" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xbrldt:contextElement="segment" xlink:from="loc_VSTARelatedPartyTransactionsByRelatedPartyAxis" xlink:to="loc_VSTARelatedPartyDomain_10" xlink:type="arc" order="30" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_SeniorNote1Member" xlink:label="loc_VSTASeniorNote1Member_0" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTARelatedPartyDomain" xlink:to="loc_VSTASeniorNote1Member_0" xlink:type="arc" order="1" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_SeniorNote2Member" xlink:label="loc_VSTASeniorNote2Member_10" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTARelatedPartyDomain" xlink:to="loc_VSTASeniorNote2Member_10" xlink:type="arc" order="11" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_SeniorNote3Member" xlink:label="loc_VSTASeniorNote3Member_20" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTARelatedPartyDomain" xlink:to="loc_VSTASeniorNote3Member_20" xlink:type="arc" order="21" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_SeniorNote4Member" xlink:label="loc_VSTASeniorNote4Member_30" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTARelatedPartyDomain" xlink:to="loc_VSTASeniorNote4Member_30" xlink:type="arc" order="31" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_SeniorNote5Member" xlink:label="loc_VSTASeniorNote5Member_40" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTARelatedPartyDomain" xlink:to="loc_VSTASeniorNote5Member_40" xlink:type="arc" order="41" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_NoteDiscountMember" xlink:label="loc_VSTANoteDiscountMember_50" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTARelatedPartyDomain" xlink:to="loc_VSTANoteDiscountMember_50" xlink:type="arc" order="51" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_SevenPercentNotesPayableAprilTwoThousandElevenMember" xlink:label="loc_VSTASevenPercentNotesPayableAprilTwoThousandElevenMember_60" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTARelatedPartyDomain" xlink:to="loc_VSTASevenPercentNotesPayableAprilTwoThousandElevenMember_60" xlink:type="arc" order="61" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_SevenPercentNotesPayableAugustTwoThousandTwelveMember" xlink:label="loc_VSTASevenPercentNotesPayableAugustTwoThousandTwelveMember_70" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTARelatedPartyDomain" xlink:to="loc_VSTASevenPercentNotesPayableAugustTwoThousandTwelveMember_70" xlink:type="arc" order="71" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_SevenPercentNotesPayableMember" xlink:label="loc_VSTASevenPercentNotesPayableMember_80" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTARelatedPartyDomain" xlink:to="loc_VSTASevenPercentNotesPayableMember_80" xlink:type="arc" order="81" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_CurrentPortionMember" xlink:label="loc_VSTACurrentPortionMember_90" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTARelatedPartyDomain" xlink:to="loc_VSTACurrentPortionMember_90" xlink:type="arc" order="91" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_SevenPercentNotesPayableNonCurrentPortionMember" xlink:label="loc_VSTASevenPercentNotesPayableNonCurrentPortionMember_100" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTARelatedPartyDomain" xlink:to="loc_VSTASevenPercentNotesPayableNonCurrentPortionMember_100" xlink:type="arc" order="101" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_BurrPilgerMayerMember" xlink:label="loc_VSTABurrPilgerMayerMember_110" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTARelatedPartyDomain" xlink:to="loc_VSTABurrPilgerMayerMember_110" xlink:type="arc" order="111" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_DesjardinsMember" xlink:label="loc_VSTADesjardinsMember_120" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTARelatedPartyDomain" xlink:to="loc_VSTADesjardinsMember_120" xlink:type="arc" order="121" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_McCarthyTetraultMember" xlink:label="loc_VSTAMcCarthyTetraultMember_130" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTARelatedPartyDomain" xlink:to="loc_VSTAMcCarthyTetraultMember_130" xlink:type="arc" order="131" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_MayTwoThousandElevenMorrisonFoersterMember" xlink:label="loc_VSTAMayTwoThousandElevenMorrisonFoersterMember_140" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTARelatedPartyDomain" xlink:to="loc_VSTAMayTwoThousandElevenMorrisonFoersterMember_140" xlink:type="arc" order="141" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_AugustTwoThousandTwelveMorrisonAndFoersterNoteAMember" xlink:label="loc_VSTAAugustTwoThousandTwelveMorrisonAndFoersterNoteAMember_150" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTARelatedPartyDomain" xlink:to="loc_VSTAAugustTwoThousandTwelveMorrisonAndFoersterNoteAMember_150" xlink:type="arc" order="151" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_AugustTwoThousandTwelveMorrisonAndFoersterNoteBMember" xlink:label="loc_VSTAAugustTwoThousandTwelveMorrisonAndFoersterNoteBMember_160" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTARelatedPartyDomain" xlink:to="loc_VSTAAugustTwoThousandTwelveMorrisonAndFoersterNoteBMember_160" xlink:type="arc" order="161" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_NoteDiscountOneMember" xlink:label="loc_VSTANoteDiscountOneMember_170" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTARelatedPartyDomain" xlink:to="loc_VSTANoteDiscountOneMember_170" xlink:type="arc" order="171" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_SevenPointFivePercentNotesPayableMember" xlink:label="loc_VSTASevenPointFivePercentNotesPayableMember_180" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTARelatedPartyDomain" xlink:to="loc_VSTASevenPointFivePercentNotesPayableMember_180" xlink:type="arc" order="181" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_CurrentPortionOneMember" xlink:label="loc_VSTACurrentPortionOneMember_190" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTARelatedPartyDomain" xlink:to="loc_VSTACurrentPortionOneMember_190" xlink:type="arc" order="191" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_NonCurrentPortionAndDiscountMember" xlink:label="loc_VSTANonCurrentPortionAndDiscountMember_200" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTARelatedPartyDomain" xlink:to="loc_VSTANonCurrentPortionAndDiscountMember_200" xlink:type="arc" order="201" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_FivePointEightPercentAndEightPercentNotesPayableToInsurancePremiumFinancingCompanyCurrentMember" xlink:label="loc_VSTAFivePointEightPercentAndEightPercentNotesPayableToInsurancePremiumFinancingCompanyCurrentMember_210" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTARelatedPartyDomain" xlink:to="loc_VSTAFivePointEightPercentAndEightPercentNotesPayableToInsurancePremiumFinancingCompanyCurrentMember_210" xlink:type="arc" order="211" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_TenPercentNotesPayableToVendorsForAccountsPayableConvertedToNotesPayableMember" xlink:label="loc_VSTATenPercentNotesPayableToVendorsForAccountsPayableConvertedToNotesPayableMember_220" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTARelatedPartyDomain" xlink:to="loc_VSTATenPercentNotesPayableToVendorsForAccountsPayableConvertedToNotesPayableMember_220" xlink:type="arc" order="221" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_CurrentPortionTwoMember" xlink:label="loc_VSTACurrentPortionTwoMember_230" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTARelatedPartyDomain" xlink:to="loc_VSTACurrentPortionTwoMember_230" xlink:type="arc" order="231" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_NonCurrentPortionMember" xlink:label="loc_VSTANonCurrentPortionMember_240" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTARelatedPartyDomain" xlink:to="loc_VSTANonCurrentPortionMember_240" xlink:type="arc" order="241" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_TenPercentNotesPayableToUnrelatedPartiesMember" xlink:label="loc_VSTATenPercentNotesPayableToUnrelatedPartiesMember_250" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTARelatedPartyDomain" xlink:to="loc_VSTATenPercentNotesPayableToUnrelatedPartiesMember_250" xlink:type="arc" order="251" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_CurrentPortionThreeMember" xlink:label="loc_VSTACurrentPortionThreeMember_260" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTARelatedPartyDomain" xlink:to="loc_VSTACurrentPortionThreeMember_260" xlink:type="arc" order="261" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_NonCurrentPortionAndDiscountOneMember" xlink:label="loc_VSTANonCurrentPortionAndDiscountOneMember_270" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTARelatedPartyDomain" xlink:to="loc_VSTANonCurrentPortionAndDiscountOneMember_270" xlink:type="arc" order="271" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_SevenPercentNotePayableToCatoHoldingMember" xlink:label="loc_VSTASevenPercentNotePayableToCatoHoldingMember_280" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTARelatedPartyDomain" xlink:to="loc_VSTASevenPercentNotePayableToCatoHoldingMember_280" xlink:type="arc" order="281" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_NoteDiscountTwoMember" xlink:label="loc_VSTANoteDiscountTwoMember_290" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTARelatedPartyDomain" xlink:to="loc_VSTANoteDiscountTwoMember_290" xlink:type="arc" order="291" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_NotesPayableToRelatedPartiesMember" xlink:label="loc_VSTANotesPayableToRelatedPartiesMember_300" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTARelatedPartyDomain" xlink:to="loc_VSTANotesPayableToRelatedPartiesMember_300" xlink:type="arc" order="301" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_CurrentPortionFourMember" xlink:label="loc_VSTACurrentPortionFourMember_310" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTARelatedPartyDomain" xlink:to="loc_VSTACurrentPortionFourMember_310" xlink:type="arc" order="311" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_NonCurrentPortionAndDiscountTwoMember" xlink:label="loc_VSTANonCurrentPortionAndDiscountTwoMember_320" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTARelatedPartyDomain" xlink:to="loc_VSTANonCurrentPortionAndDiscountTwoMember_320" xlink:type="arc" order="321" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_IssuedToPlatinumOnTwoJulyTwoThousandTwelveMember" xlink:label="loc_VSTAIssuedToPlatinumOnTwoJulyTwoThousandTwelveMember_330" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTARelatedPartyDomain" xlink:to="loc_VSTAIssuedToPlatinumOnTwoJulyTwoThousandTwelveMember_330" xlink:type="arc" order="331" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_IssuedToPlatinumOnThirtyAugustTwoThousandTwelveMember" xlink:label="loc_VSTAIssuedToPlatinumOnThirtyAugustTwoThousandTwelveMember_340" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTARelatedPartyDomain" xlink:to="loc_VSTAIssuedToPlatinumOnThirtyAugustTwoThousandTwelveMember_340" xlink:type="arc" order="341" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_SeniorNotesNonCurrentMember" xlink:label="loc_VSTASeniorNotesNonCurrentMember_350" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTARelatedPartyDomain" xlink:to="loc_VSTASeniorNotesNonCurrentMember_350" xlink:type="arc" order="351" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_FebruaryTwoThousandTwelveTwelvePercentConvertiblePromissoryNotesMember" xlink:label="loc_VSTAFebruaryTwoThousandTwelveTwelvePercentConvertiblePromissoryNotesMember_360" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTARelatedPartyDomain" xlink:to="loc_VSTAFebruaryTwoThousandTwelveTwelvePercentConvertiblePromissoryNotesMember_360" xlink:type="arc" order="361" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_TwelvePercentConvertibleNotesNetNnonCurrentMember" xlink:label="loc_VSTATwelvePercentConvertibleNotesNetNnonCurrentMember_380" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTARelatedPartyDomain" xlink:to="loc_VSTATwelvePercentConvertibleNotesNetNnonCurrentMember_380" xlink:type="arc" order="381" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_DebtInstrumentFaceAmount" xlink:label="loc_VSTADebtInstrumentFaceAmount_670" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAStatementLineItems" xlink:to="loc_VSTADebtInstrumentFaceAmount_670" xlink:type="arc" order="1" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_InterestPayableCurrentAndNoncurrent" xlink:label="loc_VSTAInterestPayableCurrentAndNoncurrent_670" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAStatementLineItems" xlink:to="loc_VSTAInterestPayableCurrentAndNoncurrent_670" xlink:type="arc" order="2" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_DebtInstrumentCarryingAmount" xlink:label="loc_VSTADebtInstrumentCarryingAmount_670" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAStatementLineItems" xlink:to="loc_VSTADebtInstrumentCarryingAmount_670" xlink:type="arc" order="3" />
    </link:definitionLink>
    <link:definitionLink xlink:type="extended" xlink:role="http://vistagen.com/role/ConvertiblePromissoryNotesAndOtherNotesPayableDetails2" xlink:title="0046 - Disclosure - 7. Convertible Promissory Notes and Other Notes Payable (Details 2)">
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_StatementLineItems" xlink:label="loc_VSTAStatementLineItems" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_StatementTable" xlink:label="loc_VSTAStatementTable" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xbrldt:contextElement="segment" xlink:from="loc_VSTAStatementLineItems" xlink:to="loc_VSTAStatementTable" xlink:type="arc" order="10" xbrldt:closed="true" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_DebtInstrumentAxis" xlink:label="loc_VSTADebtInstrumentAxis" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_VSTAStatementTable" xlink:to="loc_VSTADebtInstrumentAxis" xlink:type="arc" order="1" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_DebtInstrumentNameDomain" xlink:label="loc_VSTADebtInstrumentNameDomain" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_VSTADebtInstrumentAxis" xlink:to="loc_VSTADebtInstrumentNameDomain" xlink:type="arc" order="20" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_DebtInstrumentNameDomain" xlink:label="loc_VSTADebtInstrumentNameDomain_10" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xbrldt:contextElement="segment" xlink:from="loc_VSTADebtInstrumentAxis" xlink:to="loc_VSTADebtInstrumentNameDomain_10" xlink:type="arc" order="30" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_ExchangeWarrantMember" xlink:label="loc_VSTAExchangeWarrantMember_0" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTADebtInstrumentNameDomain" xlink:to="loc_VSTAExchangeWarrantMember_0" xlink:type="arc" order="1" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_Oct112012WarrantMember" xlink:label="loc_VSTAOct112012WarrantMember_10" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTADebtInstrumentNameDomain" xlink:to="loc_VSTAOct112012WarrantMember_10" xlink:type="arc" order="11" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_Oct192012WarrantMember" xlink:label="loc_VSTAOct192012WarrantMember_20" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTADebtInstrumentNameDomain" xlink:to="loc_VSTAOct192012WarrantMember_20" xlink:type="arc" order="21" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_Feb222013WarrantMember" xlink:label="loc_VSTAFeb222013WarrantMember_30" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTADebtInstrumentNameDomain" xlink:to="loc_VSTAFeb222013WarrantMember_30" xlink:type="arc" order="31" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_Mar122013WarrantMember" xlink:label="loc_VSTAMar122013WarrantMember_40" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTADebtInstrumentNameDomain" xlink:to="loc_VSTAMar122013WarrantMember_40" xlink:type="arc" order="41" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_ExchangeWarrantAssumptionsAbstract" xlink:label="loc_VSTAExchangeWarrantAssumptionsAbstract_60" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAStatementLineItems" xlink:to="loc_VSTAExchangeWarrantAssumptionsAbstract_60" xlink:type="arc" order="1" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_EquityIssuancePerShareAmount" xlink:label="loc_VSTAEquityIssuancePerShareAmount_60" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAExchangeWarrantAssumptionsAbstract_60" xlink:to="loc_VSTAEquityIssuancePerShareAmount_60" xlink:type="arc" order="2" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_ExercisePriceInvestmentWarrants" xlink:label="loc_VSTAExercisePriceInvestmentWarrants_60" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAExchangeWarrantAssumptionsAbstract_60" xlink:to="loc_VSTAExercisePriceInvestmentWarrants_60" xlink:type="arc" order="3" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_FairValueAssumptionsRiskFreeInterestRate" xlink:label="loc_VSTAFairValueAssumptionsRiskFreeInterestRate_60" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAExchangeWarrantAssumptionsAbstract_60" xlink:to="loc_VSTAFairValueAssumptionsRiskFreeInterestRate_60" xlink:type="arc" order="4" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_FairValueAssumptionsWeightedAverageVolatilityRate" xlink:label="loc_VSTAFairValueAssumptionsWeightedAverageVolatilityRate_60" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAExchangeWarrantAssumptionsAbstract_60" xlink:to="loc_VSTAFairValueAssumptionsWeightedAverageVolatilityRate_60" xlink:type="arc" order="5" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_FairValueAssumptionsExpectedDividendRate" xlink:label="loc_VSTAFairValueAssumptionsExpectedDividendRate_60" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAExchangeWarrantAssumptionsAbstract_60" xlink:to="loc_VSTAFairValueAssumptionsExpectedDividendRate_60" xlink:type="arc" order="6" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_FairValueInputsPriceEarningsRatioMultiple" xlink:label="loc_VSTAFairValueInputsPriceEarningsRatioMultiple_60" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAExchangeWarrantAssumptionsAbstract_60" xlink:to="loc_VSTAFairValueInputsPriceEarningsRatioMultiple_60" xlink:type="arc" order="7" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_ExchangeWarrantNumberOfShares" xlink:label="loc_VSTAExchangeWarrantNumberOfShares_60" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAExchangeWarrantAssumptionsAbstract_60" xlink:to="loc_VSTAExchangeWarrantNumberOfShares_60" xlink:type="arc" order="8" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_FairValueAtDateOfIssuance" xlink:label="loc_VSTAFairValueAtDateOfIssuance_60" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAExchangeWarrantAssumptionsAbstract_60" xlink:to="loc_VSTAFairValueAtDateOfIssuance_60" xlink:type="arc" order="9" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_ComponentsOfDiscountAndEffectiveInterestRateForInvestmentNotes" xlink:label="loc_VSTAComponentsOfDiscountAndEffectiveInterestRateForInvestmentNotes_60" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAStatementLineItems" xlink:to="loc_VSTAComponentsOfDiscountAndEffectiveInterestRateForInvestmentNotes_60" xlink:type="arc" order="11" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_DebtConversionConvertedInstrumentAmount1" xlink:label="loc_VSTADebtConversionConvertedInstrumentAmount1_60" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAComponentsOfDiscountAndEffectiveInterestRateForInvestmentNotes_60" xlink:to="loc_VSTADebtConversionConvertedInstrumentAmount1_60" xlink:type="arc" order="12" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_DiscountAttributableToFairValueOfWarrant" xlink:label="loc_VSTADiscountAttributableToFairValueOfWarrant_60" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAComponentsOfDiscountAndEffectiveInterestRateForInvestmentNotes_60" xlink:to="loc_VSTADiscountAttributableToFairValueOfWarrant_60" xlink:type="arc" order="13" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_DiscountAttributableToBeneficialConversionFeature" xlink:label="loc_VSTADiscountAttributableToBeneficialConversionFeature_60" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAComponentsOfDiscountAndEffectiveInterestRateForInvestmentNotes_60" xlink:to="loc_VSTADiscountAttributableToBeneficialConversionFeature_60" xlink:type="arc" order="14" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_InceptionDateCarryingValue" xlink:label="loc_VSTAInceptionDateCarryingValue_60" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAComponentsOfDiscountAndEffectiveInterestRateForInvestmentNotes_60" xlink:to="loc_VSTAInceptionDateCarryingValue_60" xlink:type="arc" order="15" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_DebtInstrumentConvertibleEffectiveInterestRate" xlink:label="loc_VSTADebtInstrumentConvertibleEffectiveInterestRate_60" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAComponentsOfDiscountAndEffectiveInterestRateForInvestmentNotes_60" xlink:to="loc_VSTADebtInstrumentConvertibleEffectiveInterestRate_60" xlink:type="arc" order="16" />
    </link:definitionLink>
    <link:definitionLink xlink:type="extended" xlink:role="http://vistagen.com/role/ConvertiblePromissoryNotesAndOtherNotesPayableDetails1" xlink:title="0047 - Disclosure - 7. Convertible Promissory Notes and Other Notes Payable (Details 1)">
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_StatementLineItems" xlink:label="loc_VSTAStatementLineItems" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_StatementTable" xlink:label="loc_VSTAStatementTable" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xbrldt:contextElement="segment" xlink:from="loc_VSTAStatementLineItems" xlink:to="loc_VSTAStatementTable" xlink:type="arc" order="10" xbrldt:closed="true" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_ShortTermDebtTypeAxis" xlink:label="loc_VSTAShortTermDebtTypeAxis" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_VSTAStatementTable" xlink:to="loc_VSTAShortTermDebtTypeAxis" xlink:type="arc" order="1" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_ShortTermDebtTypeDomain" xlink:label="loc_VSTAShortTermDebtTypeDomain" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_VSTAShortTermDebtTypeAxis" xlink:to="loc_VSTAShortTermDebtTypeDomain" xlink:type="arc" order="20" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_ShortTermDebtTypeDomain" xlink:label="loc_VSTAShortTermDebtTypeDomain_10" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xbrldt:contextElement="segment" xlink:from="loc_VSTAShortTermDebtTypeAxis" xlink:to="loc_VSTAShortTermDebtTypeDomain_10" xlink:type="arc" order="30" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_PreModificationMember" xlink:label="loc_VSTAPreModificationMember_0" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAShortTermDebtTypeDomain" xlink:to="loc_VSTAPreModificationMember_0" xlink:type="arc" order="1" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_PostModificationMember" xlink:label="loc_VSTAPostModificationMember_10" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAShortTermDebtTypeDomain" xlink:to="loc_VSTAPostModificationMember_10" xlink:type="arc" order="11" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_MarketPricePerShare" xlink:label="loc_VSTAMarketPricePerShare_30" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAStatementLineItems" xlink:to="loc_VSTAMarketPricePerShare_30" xlink:type="arc" order="0" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_FairValueAssumptionsExercisePrice1" xlink:label="loc_VSTAFairValueAssumptionsExercisePrice1_30" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAStatementLineItems" xlink:to="loc_VSTAFairValueAssumptionsExercisePrice1_30" xlink:type="arc" order="1" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_FairValueAssumptionsRiskFreeInterestRate" xlink:label="loc_VSTAFairValueAssumptionsRiskFreeInterestRate_30" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAStatementLineItems" xlink:to="loc_VSTAFairValueAssumptionsRiskFreeInterestRate_30" xlink:type="arc" order="2" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_FairValueAssumptionsExpectedTerm" xlink:label="loc_VSTAFairValueAssumptionsExpectedTerm_30" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAStatementLineItems" xlink:to="loc_VSTAFairValueAssumptionsExpectedTerm_30" xlink:type="arc" order="3" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_FairValueAssumptionsExpectedVolatilityRate" xlink:label="loc_VSTAFairValueAssumptionsExpectedVolatilityRate_30" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAStatementLineItems" xlink:to="loc_VSTAFairValueAssumptionsExpectedVolatilityRate_30" xlink:type="arc" order="4" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_FairValueAssumptionsExpectedDividendRate" xlink:label="loc_VSTAFairValueAssumptionsExpectedDividendRate_30" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAStatementLineItems" xlink:to="loc_VSTAFairValueAssumptionsExpectedDividendRate_30" xlink:type="arc" order="5" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_FairValuePerShare" xlink:label="loc_VSTAFairValuePerShare_30" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAStatementLineItems" xlink:to="loc_VSTAFairValuePerShare_30" xlink:type="arc" order="6" />
    </link:definitionLink>
    <link:definitionLink xlink:type="extended" xlink:role="http://vistagen.com/role/ConvertiblePromissoryNotesAndOtherNotesPayableDetailsTextuals" xlink:title="0048 - Disclosure - 7. Convertible Promissory Notes and Other Notes Payable (Details Textuals)">
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_DebtInstrumentLineItems" xlink:label="loc_VSTADebtInstrumentLineItems" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_DebtInstrumentTable" xlink:label="loc_VSTADebtInstrumentTable" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xbrldt:contextElement="segment" xlink:from="loc_VSTADebtInstrumentLineItems" xlink:to="loc_VSTADebtInstrumentTable" xlink:type="arc" order="10" xbrldt:closed="true" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_DebtInstrumentAxis" xlink:label="loc_VSTADebtInstrumentAxis" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_VSTADebtInstrumentTable" xlink:to="loc_VSTADebtInstrumentAxis" xlink:type="arc" order="1" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_DebtInstrumentNameDomain" xlink:label="loc_VSTADebtInstrumentNameDomain" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_VSTADebtInstrumentAxis" xlink:to="loc_VSTADebtInstrumentNameDomain" xlink:type="arc" order="20" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_DebtInstrumentNameDomain" xlink:label="loc_VSTADebtInstrumentNameDomain_10" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xbrldt:contextElement="segment" xlink:from="loc_VSTADebtInstrumentAxis" xlink:to="loc_VSTADebtInstrumentNameDomain_10" xlink:type="arc" order="30" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_February2012ConvertibleNotes12PercentMember" xlink:label="loc_VSTAFebruary2012ConvertibleNotes12PercentMember_0" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTADebtInstrumentNameDomain" xlink:to="loc_VSTAFebruary2012ConvertibleNotes12PercentMember_0" xlink:type="arc" order="1" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_RegistrationPaymentArrangementAccrualCarryingValue" xlink:label="loc_VSTARegistrationPaymentArrangementAccrualCarryingValue_20" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTADebtInstrumentLineItems" xlink:to="loc_VSTARegistrationPaymentArrangementAccrualCarryingValue_20" xlink:type="arc" order="1" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_July2012PlatinumNoteAmount" xlink:label="loc_VSTAJuly2012PlatinumNoteAmount_20" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTADebtInstrumentLineItems" xlink:to="loc_VSTAJuly2012PlatinumNoteAmount_20" xlink:type="arc" order="3" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_August2012PlatinumNote" xlink:label="loc_VSTAAugust2012PlatinumNote_20" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTADebtInstrumentLineItems" xlink:to="loc_VSTAAugust2012PlatinumNote_20" xlink:type="arc" order="4" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_JulyAndAugustNoteRate" xlink:label="loc_VSTAJulyAndAugustNoteRate_20" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTADebtInstrumentLineItems" xlink:to="loc_VSTAJulyAndAugustNoteRate_20" xlink:type="arc" order="5" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_ExpectedGrossNoteProceeds" xlink:label="loc_VSTAExpectedGrossNoteProceeds_20" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTADebtInstrumentLineItems" xlink:to="loc_VSTAExpectedGrossNoteProceeds_20" xlink:type="arc" order="6" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_February2012Note" xlink:label="loc_VSTAFebruary2012Note_20" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTADebtInstrumentLineItems" xlink:to="loc_VSTAFebruary2012Note_20" xlink:type="arc" order="7" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_FebruaryNoteRate" xlink:label="loc_VSTAFebruaryNoteRate_20" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTADebtInstrumentLineItems" xlink:to="loc_VSTAFebruaryNoteRate_20" xlink:type="arc" order="8" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_WarrantValue" xlink:label="loc_VSTAWarrantValue_20" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTADebtInstrumentLineItems" xlink:to="loc_VSTAWarrantValue_20" xlink:type="arc" order="9" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_AggregateShareValue" xlink:label="loc_VSTAAggregateShareValue_20" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTADebtInstrumentLineItems" xlink:to="loc_VSTAAggregateShareValue_20" xlink:type="arc" order="10" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_RegistrationRightsAgreementLiability" xlink:label="loc_VSTARegistrationRightsAgreementLiability_20" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTADebtInstrumentLineItems" xlink:to="loc_VSTARegistrationRightsAgreementLiability_20" xlink:type="arc" order="11" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_October2012PlatinumNotePrincipalAmount" xlink:label="loc_VSTAOctober2012PlatinumNotePrincipalAmount_20" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTADebtInstrumentLineItems" xlink:to="loc_VSTAOctober2012PlatinumNotePrincipalAmount_20" xlink:type="arc" order="12" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_October2012PlatinumNoteTranchAmount" xlink:label="loc_VSTAOctober2012PlatinumNoteTranchAmount_20" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTADebtInstrumentLineItems" xlink:to="loc_VSTAOctober2012PlatinumNoteTranchAmount_20" xlink:type="arc" order="13" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_October2012PlatinumNoteGrossProceeds" xlink:label="loc_VSTAOctober2012PlatinumNoteGrossProceeds_20" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTADebtInstrumentLineItems" xlink:to="loc_VSTAOctober2012PlatinumNoteGrossProceeds_20" xlink:type="arc" order="14" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_PrivatePlacements" xlink:label="loc_VSTAPrivatePlacements_20" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTADebtInstrumentLineItems" xlink:to="loc_VSTAPrivatePlacements_20" xlink:type="arc" order="15" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_ProceedsFromIssuancesOfPrivatePlacement" xlink:label="loc_VSTAProceedsFromIssuancesOfPrivatePlacement_20" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTADebtInstrumentLineItems" xlink:to="loc_VSTAProceedsFromIssuancesOfPrivatePlacement_20" xlink:type="arc" order="16" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_PrivatePlacementUnitPrice" xlink:label="loc_VSTAPrivatePlacementUnitPrice_20" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTADebtInstrumentLineItems" xlink:to="loc_VSTAPrivatePlacementUnitPrice_20" xlink:type="arc" order="17" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_FinancingRequiredToSellNote" xlink:label="loc_VSTAFinancingRequiredToSellNote_20" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTADebtInstrumentLineItems" xlink:to="loc_VSTAFinancingRequiredToSellNote_20" xlink:type="arc" order="18" />
    </link:definitionLink>
    <link:definitionLink xlink:type="extended" xlink:role="http://vistagen.com/role/ConvertiblePromissoryNotesAndOtherNotesPayableDetailsTextuals2" xlink:title="0049 - Disclosure - 7. Convertible Promissory Notes and Other Notes Payable (Details Textuals 2)">
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_DebtInstrumentLineItems" xlink:label="loc_VSTADebtInstrumentLineItems" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_DebtInstrumentTable" xlink:label="loc_VSTADebtInstrumentTable" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xbrldt:contextElement="segment" xlink:from="loc_VSTADebtInstrumentLineItems" xlink:to="loc_VSTADebtInstrumentTable" xlink:type="arc" order="10" xbrldt:closed="true" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.sec.gov/dei/2012/dei-2012-01-31.xsd#dei_LegalEntityAxis" xlink:label="loc_VSTALegalEntityAxis" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_VSTADebtInstrumentTable" xlink:to="loc_VSTALegalEntityAxis" xlink:type="arc" order="1" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.sec.gov/dei/2012/dei-2012-01-31.xsd#dei_EntityDomain" xlink:label="loc_VSTAEntityDomain" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_VSTALegalEntityAxis" xlink:to="loc_VSTAEntityDomain" xlink:type="arc" order="20" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.sec.gov/dei/2012/dei-2012-01-31.xsd#dei_EntityDomain" xlink:label="loc_VSTAEntityDomain_10" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xbrldt:contextElement="segment" xlink:from="loc_VSTALegalEntityAxis" xlink:to="loc_VSTAEntityDomain_10" xlink:type="arc" order="30" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_CatoHoldingCompanyMember" xlink:label="loc_VSTACatoHoldingCompanyMember_0" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAEntityDomain" xlink:to="loc_VSTACatoHoldingCompanyMember_0" xlink:type="arc" order="1" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_UnsecuredLongTermDebt" xlink:label="loc_VSTAUnsecuredLongTermDebt_20" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTADebtInstrumentLineItems" xlink:to="loc_VSTAUnsecuredLongTermDebt_20" xlink:type="arc" order="1" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableNumber" xlink:label="loc_VSTAShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableNumber_20" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTADebtInstrumentLineItems" xlink:to="loc_VSTAShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableNumber_20" xlink:type="arc" order="2" />
    </link:definitionLink>
    <link:definitionLink xlink:type="extended" xlink:role="http://vistagen.com/role/CapitalStockDetails" xlink:title="0050 - Disclosure - 9. Capital Stock (Details)">
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:label="loc_VSTAShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable" xlink:label="loc_VSTAScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xbrldt:contextElement="segment" xlink:from="loc_VSTAShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:to="loc_VSTAScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable" xlink:type="arc" order="10" xbrldt:closed="true" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_AwardTypeAxis" xlink:label="loc_VSTAAwardTypeAxis" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_VSTAScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable" xlink:to="loc_VSTAAwardTypeAxis" xlink:type="arc" order="1" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:label="loc_VSTAShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_VSTAAwardTypeAxis" xlink:to="loc_VSTAShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:type="arc" order="20" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:label="loc_VSTAShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_10" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xbrldt:contextElement="segment" xlink:from="loc_VSTAAwardTypeAxis" xlink:to="loc_VSTAShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_10" xlink:type="arc" order="30" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_PreModificationWarrantsMember" xlink:label="loc_VSTAPreModificationWarrantsMember_0" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:to="loc_VSTAPreModificationWarrantsMember_0" xlink:type="arc" order="1" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_PostModificationWarrantsMember" xlink:label="loc_VSTAPostModificationWarrantsMember_10" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:to="loc_VSTAPostModificationWarrantsMember_10" xlink:type="arc" order="11" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsAndMethodologyAbstract" xlink:label="loc_VSTAShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsAndMethodologyAbstract_30" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:to="loc_VSTAShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsAndMethodologyAbstract_30" xlink:type="arc" order="0" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_MarketPricePerShare" xlink:label="loc_VSTAMarketPricePerShare_30" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsAndMethodologyAbstract_30" xlink:to="loc_VSTAMarketPricePerShare_30" xlink:type="arc" order="1" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_ExercisePricePerShareWeightedAvg" xlink:label="loc_VSTAExercisePricePerShareWeightedAvg_30" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsAndMethodologyAbstract_30" xlink:to="loc_VSTAExercisePricePerShareWeightedAvg_30" xlink:type="arc" order="2" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeUpperRangeLimit" xlink:label="loc_VSTAShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeUpperRangeLimit_30" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsAndMethodologyAbstract_30" xlink:to="loc_VSTAShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeUpperRangeLimit_30" xlink:type="arc" order="3" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRateMinimum" xlink:label="loc_VSTAShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRateMinimum_30" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsAndMethodologyAbstract_30" xlink:to="loc_VSTAShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRateMinimum_30" xlink:type="arc" order="4" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRateMaximum" xlink:label="loc_VSTAShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRateMaximum_30" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsAndMethodologyAbstract_30" xlink:to="loc_VSTAShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRateMaximum_30" xlink:type="arc" order="5" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardFairValueAssumptionsExpectedTerm1" xlink:label="loc_VSTASharebasedCompensationArrangementBySharebasedPaymentAwardFairValueAssumptionsExpectedTerm1_30" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsAndMethodologyAbstract_30" xlink:to="loc_VSTASharebasedCompensationArrangementBySharebasedPaymentAwardFairValueAssumptionsExpectedTerm1_30" xlink:type="arc" order="6" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_ExpectedTermYearsMaximum" xlink:label="loc_VSTAExpectedTermYearsMaximum_30" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsAndMethodologyAbstract_30" xlink:to="loc_VSTAExpectedTermYearsMaximum_30" xlink:type="arc" order="7" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRateMinimum" xlink:label="loc_VSTAShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRateMinimum_30" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsAndMethodologyAbstract_30" xlink:to="loc_VSTAShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRateMinimum_30" xlink:type="arc" order="8" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRateMaximum" xlink:label="loc_VSTAShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRateMaximum_30" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsAndMethodologyAbstract_30" xlink:to="loc_VSTAShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRateMaximum_30" xlink:type="arc" order="9" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate" xlink:label="loc_VSTAShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate_30" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsAndMethodologyAbstract_30" xlink:to="loc_VSTAShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate_30" xlink:type="arc" order="10" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_WeightedAverageFairValuePerShare" xlink:label="loc_VSTAWeightedAverageFairValuePerShare_30" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsAndMethodologyAbstract_30" xlink:to="loc_VSTAWeightedAverageFairValuePerShare_30" xlink:type="arc" order="11" />
    </link:definitionLink>
    <link:definitionLink xlink:type="extended" xlink:role="http://vistagen.com/role/CapitalStockDetails1" xlink:title="0051 - Disclosure - 9. Capital Stock (Details 1)">
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:label="loc_VSTAShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable" xlink:label="loc_VSTAScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xbrldt:contextElement="segment" xlink:from="loc_VSTAShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:to="loc_VSTAScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable" xlink:type="arc" order="10" xbrldt:closed="true" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_RangeAxis" xlink:label="loc_VSTARangeAxis" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_VSTAScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable" xlink:to="loc_VSTARangeAxis" xlink:type="arc" order="1" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_RangeMember" xlink:label="loc_VSTARangeMember" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_VSTARangeAxis" xlink:to="loc_VSTARangeMember" xlink:type="arc" order="20" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_RangeMember" xlink:label="loc_VSTARangeMember_10" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xbrldt:contextElement="segment" xlink:from="loc_VSTARangeAxis" xlink:to="loc_VSTARangeMember_10" xlink:type="arc" order="30" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_ShareBasedCompensationWarrantsTenMember" xlink:label="loc_VSTAShareBasedCompensationWarrantsTenMember_0" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTARangeMember" xlink:to="loc_VSTAShareBasedCompensationWarrantsTenMember_0" xlink:type="arc" order="1" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_ShareBasedCompensationWarrantsOneMember" xlink:label="loc_VSTAShareBasedCompensationWarrantsOneMember_10" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTARangeMember" xlink:to="loc_VSTAShareBasedCompensationWarrantsOneMember_10" xlink:type="arc" order="11" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_ShareBasedCompensationWarrantsTwoMember" xlink:label="loc_VSTAShareBasedCompensationWarrantsTwoMember_20" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTARangeMember" xlink:to="loc_VSTAShareBasedCompensationWarrantsTwoMember_20" xlink:type="arc" order="21" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_ShareBasedCompensationWarrantsTwelveMember" xlink:label="loc_VSTAShareBasedCompensationWarrantsTwelveMember_30" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTARangeMember" xlink:to="loc_VSTAShareBasedCompensationWarrantsTwelveMember_30" xlink:type="arc" order="31" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_ShareBasedCompensationWarrantsFourMember" xlink:label="loc_VSTAShareBasedCompensationWarrantsFourMember_40" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTARangeMember" xlink:to="loc_VSTAShareBasedCompensationWarrantsFourMember_40" xlink:type="arc" order="41" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_ShareBasedCompensationWarrantsFiveMember" xlink:label="loc_VSTAShareBasedCompensationWarrantsFiveMember_50" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTARangeMember" xlink:to="loc_VSTAShareBasedCompensationWarrantsFiveMember_50" xlink:type="arc" order="51" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_ShareBasedCompensationWarrantsSixMember" xlink:label="loc_VSTAShareBasedCompensationWarrantsSixMember_60" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTARangeMember" xlink:to="loc_VSTAShareBasedCompensationWarrantsSixMember_60" xlink:type="arc" order="61" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_ShareBasedCompensationWarrantsSevenMember" xlink:label="loc_VSTAShareBasedCompensationWarrantsSevenMember_70" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTARangeMember" xlink:to="loc_VSTAShareBasedCompensationWarrantsSevenMember_70" xlink:type="arc" order="71" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_ShareBasedCompensationWarrantsEightMember" xlink:label="loc_VSTAShareBasedCompensationWarrantsEightMember_80" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTARangeMember" xlink:to="loc_VSTAShareBasedCompensationWarrantsEightMember_80" xlink:type="arc" order="81" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_ShareBasedCompensationWarrantsNineMember" xlink:label="loc_VSTAShareBasedCompensationWarrantsNineMember_90" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTARangeMember" xlink:to="loc_VSTAShareBasedCompensationWarrantsNineMember_90" xlink:type="arc" order="91" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_ShareBasedCompensationWarrantsThirteenMember" xlink:label="loc_VSTAShareBasedCompensationWarrantsThirteenMember_100" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTARangeMember" xlink:to="loc_VSTAShareBasedCompensationWarrantsThirteenMember_100" xlink:type="arc" order="101" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_ShareBasedCompensationWarrantsElevenMember" xlink:label="loc_VSTAShareBasedCompensationWarrantsElevenMember_110" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTARangeMember" xlink:to="loc_VSTAShareBasedCompensationWarrantsElevenMember_110" xlink:type="arc" order="111" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_ShareBasedCompensationWarrantsFourteenMember" xlink:label="loc_VSTAShareBasedCompensationWarrantsFourteenMember_120" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTARangeMember" xlink:to="loc_VSTAShareBasedCompensationWarrantsFourteenMember_120" xlink:type="arc" order="121" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_ShareBasedCompensationWarrantsMember" xlink:label="loc_VSTAShareBasedCompensationWarrantsMember_130" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTARangeMember" xlink:to="loc_VSTAShareBasedCompensationWarrantsMember_130" xlink:type="arc" order="131" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_WarrantsOptionAbstract" xlink:label="loc_VSTAWarrantsOptionAbstract_150" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:to="loc_VSTAWarrantsOptionAbstract_150" xlink:type="arc" order="0" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_ExercisePrice" xlink:label="loc_VSTAExercisePrice_150" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAWarrantsOptionAbstract_150" xlink:to="loc_VSTAExercisePrice_150" xlink:type="arc" order="1" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_ExpirationDate" xlink:label="loc_VSTAExpirationDate_150" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAWarrantsOptionAbstract_150" xlink:to="loc_VSTAExpirationDate_150" xlink:type="arc" order="2" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsOutstandingNumber" xlink:label="loc_VSTAShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsOutstandingNumber_150" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAWarrantsOptionAbstract_150" xlink:to="loc_VSTAShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsOutstandingNumber_150" xlink:type="arc" order="3" />
    </link:definitionLink>
    <link:definitionLink xlink:type="extended" xlink:role="http://vistagen.com/role/CapitalStockDetails2" xlink:title="0052 - Disclosure - Capital Stock (Details 2)" />
    <link:definitionLink xlink:type="extended" xlink:role="http://vistagen.com/role/CapitalStockDetailsTextuals" xlink:title="0053 - Disclosure - 9. Capital Stock (Details Textuals)">
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_StatementLineItems" xlink:label="loc_VSTAStatementLineItems" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_StatementTable" xlink:label="loc_VSTAStatementTable" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xbrldt:contextElement="segment" xlink:from="loc_VSTAStatementLineItems" xlink:to="loc_VSTAStatementTable" xlink:type="arc" order="10" xbrldt:closed="true" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_StatementEquityComponentsAxis" xlink:label="loc_VSTAStatementEquityComponentsAxis" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_VSTAStatementTable" xlink:to="loc_VSTAStatementEquityComponentsAxis" xlink:type="arc" order="1" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_EquityComponentDomain" xlink:label="loc_VSTAEquityComponentDomain" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_VSTAStatementEquityComponentsAxis" xlink:to="loc_VSTAEquityComponentDomain" xlink:type="arc" order="20" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_EquityComponentDomain" xlink:label="loc_VSTAEquityComponentDomain_10" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xbrldt:contextElement="segment" xlink:from="loc_VSTAStatementEquityComponentsAxis" xlink:to="loc_VSTAEquityComponentDomain_10" xlink:type="arc" order="30" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_InvestorRelationServicesMember" xlink:label="loc_VSTAInvestorRelationServicesMember_0" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAEquityComponentDomain" xlink:to="loc_VSTAInvestorRelationServicesMember_0" xlink:type="arc" order="1" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_InvestorRelationsAndPublicCompanyServicesMember" xlink:label="loc_VSTAInvestorRelationsAndPublicCompanyServicesMember_10" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAEquityComponentDomain" xlink:to="loc_VSTAInvestorRelationsAndPublicCompanyServicesMember_10" xlink:type="arc" order="11" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_AdditionalInvestorRelationsServicesMember" xlink:label="loc_VSTAAdditionalInvestorRelationsServicesMember_20" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAEquityComponentDomain" xlink:to="loc_VSTAAdditionalInvestorRelationsServicesMember_20" xlink:type="arc" order="21" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_WarrantModificationsMember" xlink:label="loc_VSTAWarrantModificationsMember_30" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAEquityComponentDomain" xlink:to="loc_VSTAWarrantModificationsMember_30" xlink:type="arc" order="31" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_ForegoingExercisesMember" xlink:label="loc_VSTAForegoingExercisesMember_40" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAEquityComponentDomain" xlink:to="loc_VSTAForegoingExercisesMember_40" xlink:type="arc" order="41" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_PlatinumMember" xlink:label="loc_VSTAPlatinumMember_50" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAEquityComponentDomain" xlink:to="loc_VSTAPlatinumMember_50" xlink:type="arc" order="51" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_StatementClassOfStockAxis" xlink:label="loc_VSTAStatementClassOfStockAxis" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_VSTAStatementTable" xlink:to="loc_VSTAStatementClassOfStockAxis" xlink:type="arc" order="2" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_ClassOfStockDomain" xlink:label="loc_VSTAClassOfStockDomain" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_VSTAStatementClassOfStockAxis" xlink:to="loc_VSTAClassOfStockDomain" xlink:type="arc" order="20" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_ClassOfStockDomain" xlink:label="loc_VSTAClassOfStockDomain_10" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xbrldt:contextElement="segment" xlink:from="loc_VSTAStatementClassOfStockAxis" xlink:to="loc_VSTAClassOfStockDomain_10" xlink:type="arc" order="30" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_SeriesAPreferredStockMember" xlink:label="loc_VSTASeriesAPreferredStockMember_50" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAClassOfStockDomain" xlink:to="loc_VSTASeriesAPreferredStockMember_50" xlink:type="arc" order="352" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_QualifiedFinancingMember" xlink:label="loc_VSTAQualifiedFinancingMember_60" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAClassOfStockDomain" xlink:to="loc_VSTAQualifiedFinancingMember_60" xlink:type="arc" order="362" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardSharesPurchasedForAward" xlink:label="loc_VSTAShareBasedCompensationArrangementByShareBasedPaymentAwardSharesPurchasedForAward_80" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAStatementLineItems" xlink:to="loc_VSTAShareBasedCompensationArrangementByShareBasedPaymentAwardSharesPurchasedForAward_80" xlink:type="arc" order="1" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.sec.gov/invest/2012/invest-2012-01-31.xsd#invest_InvestmentOptionsExercisePrice" xlink:label="loc_VSTAInvestmentOptionsExercisePrice_80" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAStatementLineItems" xlink:to="loc_VSTAInvestmentOptionsExercisePrice_80" xlink:type="arc" order="2" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_StockAndWarrantsIssuedDuringPeriodValuePreferredStockAndWarrants" xlink:label="loc_VSTAStockAndWarrantsIssuedDuringPeriodValuePreferredStockAndWarrants_80" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAStatementLineItems" xlink:to="loc_VSTAStockAndWarrantsIssuedDuringPeriodValuePreferredStockAndWarrants_80" xlink:type="arc" order="3" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_SharePrice1" xlink:label="loc_VSTASharePrice1_80" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAStatementLineItems" xlink:to="loc_VSTASharePrice1_80" xlink:type="arc" order="4" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_ShareBasedCompensationArrangementByShareBasedPaymentAwardPerShareWeightedAveragePriceOfSharesPurchased1" xlink:label="loc_VSTAShareBasedCompensationArrangementByShareBasedPaymentAwardPerShareWeightedAveragePriceOfSharesPurchased1_80" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAStatementLineItems" xlink:to="loc_VSTAShareBasedCompensationArrangementByShareBasedPaymentAwardPerShareWeightedAveragePriceOfSharesPurchased1_80" xlink:type="arc" order="5" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_FairValueAssumptionsRiskFreeInterestRate" xlink:label="loc_VSTAFairValueAssumptionsRiskFreeInterestRate_80" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAStatementLineItems" xlink:to="loc_VSTAFairValueAssumptionsRiskFreeInterestRate_80" xlink:type="arc" order="6" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_ContractualTerm1" xlink:label="loc_VSTAContractualTerm1_80" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAStatementLineItems" xlink:to="loc_VSTAContractualTerm1_80" xlink:type="arc" order="7" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_FairValueAssumptionsWeightedAverageVolatilityRate" xlink:label="loc_VSTAFairValueAssumptionsWeightedAverageVolatilityRate_80" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAStatementLineItems" xlink:to="loc_VSTAFairValueAssumptionsWeightedAverageVolatilityRate_80" xlink:type="arc" order="8" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_FairValueAssumptionsExpectedDividendRate" xlink:label="loc_VSTAFairValueAssumptionsExpectedDividendRate_80" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAStatementLineItems" xlink:to="loc_VSTAFairValueAssumptionsExpectedDividendRate_80" xlink:type="arc" order="9" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant1" xlink:label="loc_VSTAShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant1_80" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAStatementLineItems" xlink:to="loc_VSTAShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant1_80" xlink:type="arc" order="10" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_CommonStockValue1" xlink:label="loc_VSTACommonStockValue1_80" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAStatementLineItems" xlink:to="loc_VSTACommonStockValue1_80" xlink:type="arc" order="11" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_ProceedsFromIssuanceOfCommonStock" xlink:label="loc_VSTAProceedsFromIssuanceOfCommonStock_80" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAStatementLineItems" xlink:to="loc_VSTAProceedsFromIssuanceOfCommonStock_80" xlink:type="arc" order="13" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_AmountsDueForServices" xlink:label="loc_VSTAAmountsDueForServices_80" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAStatementLineItems" xlink:to="loc_VSTAAmountsDueForServices_80" xlink:type="arc" order="14" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_CommonStockPurchseDiscription" xlink:label="loc_VSTACommonStockPurchseDiscription_80" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAStatementLineItems" xlink:to="loc_VSTACommonStockPurchseDiscription_80" xlink:type="arc" order="15" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_IncreasedValueOfWarrantsExercised" xlink:label="loc_VSTAIncreasedValueOfWarrantsExercised_80" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAStatementLineItems" xlink:to="loc_VSTAIncreasedValueOfWarrantsExercised_80" xlink:type="arc" order="16" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_PreferredStockSharesIssued" xlink:label="loc_VSTAPreferredStockSharesIssued_80" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAStatementLineItems" xlink:to="loc_VSTAPreferredStockSharesIssued_80" xlink:type="arc" order="18" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_CommonStockOwned" xlink:label="loc_VSTACommonStockOwned_80" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAStatementLineItems" xlink:to="loc_VSTACommonStockOwned_80" xlink:type="arc" order="19" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_SecuredConvertiblePromissoryNote1" xlink:label="loc_VSTASecuredConvertiblePromissoryNote1_80" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAStatementLineItems" xlink:to="loc_VSTASecuredConvertiblePromissoryNote1_80" xlink:type="arc" order="20" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_ConvertibleNotesPayable" xlink:label="loc_VSTAConvertibleNotesPayable_80" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAStatementLineItems" xlink:to="loc_VSTAConvertibleNotesPayable_80" xlink:type="arc" order="21" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_FinancingTransactionsGrossProceeds" xlink:label="loc_VSTAFinancingTransactionsGrossProceeds_80" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAStatementLineItems" xlink:to="loc_VSTAFinancingTransactionsGrossProceeds_80" xlink:type="arc" order="22" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_InvestmentInQualifiedFinancing" xlink:label="loc_VSTAInvestmentInQualifiedFinancing_80" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAStatementLineItems" xlink:to="loc_VSTAInvestmentInQualifiedFinancing_80" xlink:type="arc" order="23" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_AmountOfCommitmentsFromOtherInvestors" xlink:label="loc_VSTAAmountOfCommitmentsFromOtherInvestors_80" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAStatementLineItems" xlink:to="loc_VSTAAmountOfCommitmentsFromOtherInvestors_80" xlink:type="arc" order="24" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_PeriodOfCommitmentsFromOtherInvestors2" xlink:label="loc_VSTAPeriodOfCommitmentsFromOtherInvestors2_80" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAStatementLineItems" xlink:to="loc_VSTAPeriodOfCommitmentsFromOtherInvestors2_80" xlink:type="arc" order="25" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_CommonStockParOrStatedValuePerShare" xlink:label="loc_VSTACommonStockParOrStatedValuePerShare_80" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAStatementLineItems" xlink:to="loc_VSTACommonStockParOrStatedValuePerShare_80" xlink:type="arc" order="26" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_CommonStockSharesOutstanding" xlink:label="loc_VSTACommonStockSharesOutstanding_80" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAStatementLineItems" xlink:to="loc_VSTACommonStockSharesOutstanding_80" xlink:type="arc" order="27" />
    </link:definitionLink>
    <link:definitionLink xlink:type="extended" xlink:role="http://vistagen.com/role/ResearchAndDevelopmentExpensesDetailsNarrative" xlink:title="0054 - Disclosure - Research and Development Expenses (Details Narrative)" />
    <link:definitionLink xlink:type="extended" xlink:role="http://vistagen.com/role/IncomeTaxesDetails" xlink:title="0055 - Disclosure - Income Taxes (Details)" />
    <link:definitionLink xlink:type="extended" xlink:role="http://vistagen.com/role/IncomeTaxesDetails1" xlink:title="0056 - Disclosure - Income Taxes (Details 1)" />
    <link:definitionLink xlink:type="extended" xlink:role="http://vistagen.com/role/IncomeTaxesDetailsNarrative" xlink:title="0057 - Disclosure - Income Taxes (Details Narrative)" />
    <link:definitionLink xlink:type="extended" xlink:role="http://vistagen.com/role/StockOptionPlansAnd401KPlanDetails" xlink:title="0058 - Disclosure - Stock Option Plans and 401(k) Plan (Details)">
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_StatementLineItems" xlink:label="loc_VSTAStatementLineItems" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_StatementTable" xlink:label="loc_VSTAStatementTable" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xbrldt:contextElement="segment" xlink:from="loc_VSTAStatementLineItems" xlink:to="loc_VSTAStatementTable" xlink:type="arc" order="10" xbrldt:closed="true" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsByReportLineAxis" xlink:label="loc_VSTAScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsByReportLineAxis" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_VSTAStatementTable" xlink:to="loc_VSTAScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsByReportLineAxis" xlink:type="arc" order="1" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeDomain" xlink:label="loc_VSTAShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeDomain" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_VSTAScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsByReportLineAxis" xlink:to="loc_VSTAShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeDomain" xlink:type="arc" order="20" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeDomain" xlink:label="loc_VSTAShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeDomain_10" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xbrldt:contextElement="segment" xlink:from="loc_VSTAScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsByReportLineAxis" xlink:to="loc_VSTAShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeDomain_10" xlink:type="arc" order="30" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_MinimumMember" xlink:label="loc_VSTAMinimumMember_0" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeDomain" xlink:to="loc_VSTAMinimumMember_0" xlink:type="arc" order="1" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_MaximumMember" xlink:label="loc_VSTAMaximumMember_10" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeDomain" xlink:to="loc_VSTAMaximumMember_10" xlink:type="arc" order="11" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_ExpectedDividendYield" xlink:label="loc_VSTAExpectedDividendYield_50" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAStatementLineItems" xlink:to="loc_VSTAExpectedDividendYield_50" xlink:type="arc" order="0" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_TemporaryEquityRedemptionPricePerShare" xlink:label="loc_VSTATemporaryEquityRedemptionPricePerShare_50" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAStatementLineItems" xlink:to="loc_VSTATemporaryEquityRedemptionPricePerShare_50" xlink:type="arc" order="1" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_SharePrice" xlink:label="loc_VSTASharePrice_50" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAStatementLineItems" xlink:to="loc_VSTASharePrice_50" xlink:type="arc" order="2" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_FairValueAssumptionsRiskFreeInterestRates" xlink:label="loc_VSTAFairValueAssumptionsRiskFreeInterestRates_50" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAStatementLineItems" xlink:to="loc_VSTAFairValueAssumptionsRiskFreeInterestRates_50" xlink:type="arc" order="3" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_ExpectedYearTerm" xlink:label="loc_VSTAExpectedYearTerm_50" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAStatementLineItems" xlink:to="loc_VSTAExpectedYearTerm_50" xlink:type="arc" order="4" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_ShareBasedCompensationArrangementByShareBasedPaymentAwardVolatilityRate" xlink:label="loc_VSTAShareBasedCompensationArrangementByShareBasedPaymentAwardVolatilityRate_50" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAStatementLineItems" xlink:to="loc_VSTAShareBasedCompensationArrangementByShareBasedPaymentAwardVolatilityRate_50" xlink:type="arc" order="5" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_FairValuePerShareAtGrantDate" xlink:label="loc_VSTAFairValuePerShareAtGrantDate_50" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAStatementLineItems" xlink:to="loc_VSTAFairValuePerShareAtGrantDate_50" xlink:type="arc" order="6" />
    </link:definitionLink>
    <link:definitionLink xlink:type="extended" xlink:role="http://vistagen.com/role/StockOptionPlansAnd401KPlanDetails1" xlink:title="0059 - Disclosure - Stock Option Plans and 401(k) Plan (Details 1)" />
    <link:definitionLink xlink:type="extended" xlink:role="http://vistagen.com/role/RelatedPartyTransactionsDetailsTextuals" xlink:title="0060 - Disclosure - Related Party Transactions (Details Textuals)">
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_StatementLineItems" xlink:label="loc_VSTAStatementLineItems" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_StatementTable" xlink:label="loc_VSTAStatementTable" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xbrldt:contextElement="segment" xlink:from="loc_VSTAStatementLineItems" xlink:to="loc_VSTAStatementTable" xlink:type="arc" order="10" xbrldt:closed="true" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.sec.gov/dei/2012/dei-2012-01-31.xsd#dei_LegalEntityAxis" xlink:label="loc_VSTALegalEntityAxis" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_VSTAStatementTable" xlink:to="loc_VSTALegalEntityAxis" xlink:type="arc" order="1" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.sec.gov/dei/2012/dei-2012-01-31.xsd#dei_EntityDomain" xlink:label="loc_VSTAEntityDomain" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_VSTALegalEntityAxis" xlink:to="loc_VSTAEntityDomain" xlink:type="arc" order="20" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.sec.gov/dei/2012/dei-2012-01-31.xsd#dei_EntityDomain" xlink:label="loc_VSTAEntityDomain_10" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xbrldt:contextElement="segment" xlink:from="loc_VSTALegalEntityAxis" xlink:to="loc_VSTAEntityDomain_10" xlink:type="arc" order="30" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_CatoBioVenturesMember" xlink:label="loc_VSTACatoBioVenturesMember_0" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAEntityDomain" xlink:to="loc_VSTACatoBioVenturesMember_0" xlink:type="arc" order="1" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_InterestIncomeExpenseNet" xlink:label="loc_VSTAInterestIncomeExpenseNet_30" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAStatementLineItems" xlink:to="loc_VSTAInterestIncomeExpenseNet_30" xlink:type="arc" order="0" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_ResearchAndDevelopmentExpenseExcludingAcquiredInProcessCost" xlink:label="loc_VSTAResearchAndDevelopmentExpenseExcludingAcquiredInProcessCost_30" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAStatementLineItems" xlink:to="loc_VSTAResearchAndDevelopmentExpenseExcludingAcquiredInProcessCost_30" xlink:type="arc" order="1" />
      <link:loc xlink:type="locator" xlink:href="vsta-20130331.xsd#VSTA_CrlNoteIntrestExpense" xlink:label="loc_VSTACrlNoteIntrestExpense_30" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_VSTAStatementLineItems" xlink:to="loc_VSTACrlNoteIntrestExpense_30" xlink:type="arc" order="2" />
    </link:definitionLink>
    <link:definitionLink xlink:type="extended" xlink:role="http://vistagen.com/role/CommitmentsContingenciesGuaranteesAndIndemnificationsDetails" xlink:title="0061 - Disclosure - Commitments, Contingencies, Guarantees and Indemnifications (Details)" />
    <link:definitionLink xlink:type="extended" xlink:role="http://vistagen.com/role/CommitmentsContingenciesGuaranteesAndIndemnificationsDetails1" xlink:title="0062 - Disclosure - Commitments, Contingencies, Guarantees and Indemnifications (Details 1)" />
    <link:definitionLink xlink:type="extended" xlink:role="http://vistagen.com/role/CommitmentsContingenciesGuaranteesAndIndemnificationsDetails2" xlink:title="0063 - Disclosure - Commitments, Contingencies, Guarantees and Indemnifications (Details 2)" />
    <link:definitionLink xlink:type="extended" xlink:role="http://vistagen.com/role/CommitmentsContingenciesGuaranteesAndIndemnificationsDetailsNarrative" xlink:title="0064 - Disclosure - Commitments, Contingencies, Guarantees and Indemnifications (Details Narrative)" />
    <link:definitionLink xlink:type="extended" xlink:role="http://vistagen.com/role/SubsequentEventsDetails" xlink:title="0065 - Disclosure - Subsequent Events (Details)" />
    <link:definitionLink xlink:type="extended" xlink:role="http://vistagen.com/role/SupplementalFinancialInformationDetailsNarrative" xlink:title="0066 - Disclosure - Supplemental Financial Information (Details Narrative)" />
    <link:definitionLink xlink:type="extended" xlink:role="http://vistagen.com/role/SupplementalFinancialInformationDetails" xlink:title="0067 - Disclosure - Supplemental Financial Information (Details)" />
</link:linkbase>
