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1、Ultrahigh-resolutionmicrostructuraldiffusiontensorimagingrevealsperforantpathdegradationinagedhumansinvivoa,bc,da,b,1MichaelA.Yassa,L.TuganMuftuler,andCraigE.L.StarkabcdCenterforNeurobiologyofLearningandMemory,DepartmentofNeurobiologyandBehavior,DepartmentofRadiologicalSci
2、ences,andCenterforFunctionalOnco-Imaging,UniversityofCalifornia,Irvine,CA92697Edited*byLarryR.Squire,VeteransAffairsMedicalCenter,SanDiego,CA,andapprovedMay19,2010(receivedforreviewFebruary20,2010)Theperforantpath(PP)undergoessynapticchangesinthecourseofattemptedtoinvestig
3、atethePPinhumansinvivousingDTIinaginganddementia.Previousstudiesattemptingtoassessthepatientswithmildcognitiveimpairment(MCI)orAD.TwointegrityofthePPinhumansusingdiffusiontensorimaging(DTI)studiesreportedchangesinthePPregioninpatientswithMCI.werelimitedbylowresolutionandth
4、einabilitytoidentifyPPfibersOnestudyreportedreducedintervoxelcoherence(i.e.,thedegreespecifically.HerewepresentanapplicationofDTIatultrahighsub-ofsimilarityofadjacentvoxelorientation)(16),whereasanothermillimeterresolutionthathasallowedustosuccessfullyidentifyreportedanincre
5、aseinmeandiffusivity(ameasureofisotropicdiffusionsignalsuniquetothePPandcomparetheintensityofthesediffusion,whichincreaseswithtissuedegradation)(17).De-signalsinasampleofyoungadultsandolderadults.Wereportdirectcreasedfractionalanisotropy(FA;ameasureoftheanisotropyofevidenc
6、eofage-relatedPPdegradationinhumansinvivo.Wefinddiffusion)inparahippocampalwhitematterhasalsobeenshownnoevidenceofsuchlossinacontrolpathway,thealveus,suggestinginstudiesofpatientswithAD(18).Acrossstudies,quantificationthatthesefindingsarenotevidenceforaglobaldecline.Wealsoofs
7、malldeviationsinthedirectionofthediffusionsignalatthefindnoevidenceforspecificentorhinalgraymatteratrophy.resolutionusedwasnotpossible.Further,astheparahippocampalTheextentofPPdegradationcorrelatedwithperformanceonregionassessedalsocontainsmanyotherfibers(e.g.,theangularaword
8、-listlearningtasksensitivetohippocampaldeficits.Wealsobundle),itwasdifficulttoassesswhether
