最新Functional Magnetic Resonance Imaging - CCNL - Internal ：功能磁共振成像-省-内部教学讲义ppt.ppt

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1、FunctionalMagneticResonanceImaging-CCNL-Internal：功能磁共振成像-省-内部ChangesinBOLDactivityassociatedwithpresentationsofsinglediscreteevents.TIMEBEHAVIORALTASKREF.WAVE22secExperimentalBase22sec5minutesBlockDesignsEffectsofblockintervalonthefMRIhemodynamicresponse.Com

2、parisonofBlockvs.Event-relatedDesignsBlockdesigns–verygoodfordetectionEvent-related–verygoodforestimationofshapeandtimingofHRFLinearityThepropertywherebythecombinedresponseto2ormoreeventsisequaltothesummationoftheresponsestotheindividualeventsinisolation.Lin

3、earNon-LinearPropertiesofaLinearSystemScaling–OutputisproportionaltoinputPropertiesofaLinearSystemSuperposition–TotalresponsetoasetofinputsisequivalenttothesummationoftheindependentresponsesoftheinputsEvidenceforRoughLinearityofBOLDresponseLinearadditionofHR

4、FtoindividualstimuluseventsChallengestoLinearityRefractoryperiod–timeperiodafterstimuluspresentationduringwhichsubsequentstimulievokeareducedresponse.AsamplefMRItimecoursefromasinglevoxelinthemotorcortex.DatafromtheindividualtrialsthatmakeuppreviousfigureAve

5、ragetrialstogethertocreatemeanHRFforvoxelNeedhighsamplingrate(shortTR)toaccuratelyestimateshapeofHRFAllowsforbettertimeresolution–whichareasreachpeakfirstUseofevent-relatedfMRItostudybehavioralselection.Useofanevent-relateddesigntoseparatedifferentphasesofan

6、experimentaltask.Useofanevent-relateddesigntoseparatedifferentphasesofanexperimentaltask.PartialVolumeEffectsSmallervoxelsizes–lesslikelytohavepartialvolumeeffectsHowdodifferentpartsofvasculatureaffectBOLDsignal?BOLDsignalreflectsbothintravascular(withinvein

7、sandcapillaries)andextravascular(withintissue)signal.Capillariesthatareadjacenttobraintissue.Also,veinsthatdraindeoxyHbfrombrainLarge-vesseleffectsLargeVesselEffectsLargevolumeofbloodDrainingveinscanbedistantfromneuronsofinterestSpecificorientationwithinavox

8、elCandrainbloodfromdifferentareasofbrainTherefore,largevesselscancompromiseresolutionoffMRIEliminatinglargevesseleffectsSpatialspecificityoftheBOLDinitialdip.Allvoxelsshowingsignificantlateposit