Huk Lera Boroditsky Department of Psychology Stanford University 450 Serra Mall Stanford CA 94305 United States Neurobiology and Center for Perceptual Systems The University of Texas at Austin Austin TX 78712 United States article info Article hist ID: 34865
Download Pdf The PPT/PDF document "Brief article A motion aftereffect from ..." is the property of its rightful owner. Permission is granted to download and print the materials on this web site for personal, non-commercial use only, and to display it on your personal computer provided you do not modify the materials and that you retain all copyright notices contained in the materials. By downloading content from our website, you accept the terms of this agreement.
BriefarticleAmotionaftereffectfromvisualimageryofmotionJonathanWinawer,AlexanderC.Huk,LeraBoroditskyDepartmentofPsychology,StanfordUniversity,450SerraMall,Stanford,CA94305,UnitedStates Correspondingauthor.Tel.:+16507049702.E-mailaddress:(J.Winawer). Cognition114(2010)276…284 ContentslistsavailableatScienceDirectCognitionjournalhomepage:www.elsevier.com/locate/COGNIT involvementofdirection-selectiveneuralmechanismsKohn&Movshon,2003;Petersen,Baker,&Allman,1985;VanWezel&Britten,2002Wereasonedthatifvisualimageryofmotionreliesondirection-selectiveneuronsthatarealsoinvolvedintheperceptionofphysicalmotion,thenprolongedimageryofmotioninonedirectionshouldadaptdirection-selectiveneuronsandproduceamotionaftereffect.Inpreviousworkwehaveshownthatviewingfrozen-motionphoto-graphscanproduceamotionaftereffect(Winawer,Huk,&Boroditsky,2008).Hereweaskedwhetherimaginingmotionintheabsenceofvisualstimulicanadaptdirec-tion-selectiveneuronsandproduceamotionaftereffect.2.MethodsFiveexperimentswereconducted.Experiments1…3testedforamotionaftereffectresultingfromimaginedmo-tion.Forcomparisontotheimageryexperiments,Experi-ments4and5testedforamotionaftereffectresultingfromviewingrealmotion.Eachexperimentwasprecededbyabaselinemotionsensitivitymeasurement.Intheexperimentaltrials,participantseitherimaginedorviewedmotion,andweretestedwithmoving-dottestprobes.Thetestprobeswereusedtoassessthedegreetowhichimag-iningorviewingrealmotioncausedamotionaftereffect.2.1.ParticipantsNaïvevolunteersfromtheMIT(=64)andStanford=68)communitiesreceivedcoursecreditorwerepaidforparticipation.InExperiment1,33participantsimag-inedupwardordownwardmotion.InExperiment2,31participantsimaginedinwardoroutwardmotion.InExperiment3,30participantsalsoimaginedinwardorout-wardmotion,butwithadelayof1,4,or13sinsertedineachtrialbeforetheappearanceofthetestprobetoassessthedecayoftheaftereffect.InExperiments4and5,partic-ipantspassivelyviewedmovinggratings,eitherupwardordownward(=31),orinwardoroutward(=7).Inallexperiments,participantsviewedorimaginedthetwoopposingdirectionsofmotioninseparateblocks;nopar-ticipantsparticipatedinmorethanoneexperiment.2.2.Moving-dotteststimuliWeassessedadaptationtomotionwithastandarddirectiondiscriminationtask(Newsome&Pare,1988usedpreviouslytoquantifymotionaftereffectsfromadaptingtorealvisualmotion(Blake&Hiris,1993;Hiris&Blake,1992).Theteststimulusconsistedoflow-contrastdynamicrandomdots.Thepercentageofdotsmovingcoherentlyinaparticulardirection(motioncoherenceŽ)variedfromtrialtotrial.Thedirectionofcoherentmotionwaseitherup/down(Experiments1and4),orinward/out-ward(Experiments2,3,and5).Participantswerein-structedtoindicatethedirectionofglobalmotionbyforcedchoice(upvs.downorinwardvs.outward,depend-ingonthetypeofmotionintheexperiment).Therangeofmotioncoherencevalueswasadjustedforeachparticipantaccordingtotheirperformanceonthebaselinemotiondis-criminationtask.Participantswhofailedtodemonstratesensitivitytomotioninthebaselinetaskwereexcludedfromanalysis(seeAppendixA3.ImageryadaptationExperiments1and2testedforadaptationfrommotionimagery(Fig.1).Afterabaselinetask,participantswerefamiliarizedwiththemotionstimulitoimagine.Thestim-uliwereeitherhorizontalgratingsthatmovedupordown(Experiment1),ortwoverticalgratingsthatmovedhori-zontallyinwardoroutward(Experiment2).Thegratingsweresquarewaveluminancegratingswithaspatialfre-quencyof1cycleperdegree,andaspeedof2.7persec-ond.Tofacilitateimagery,participantswerepresentedwithatimingguide:astationary“xationsquarewhichcycledinluminanceoratonewhichcycledinpitch.Thetimingguidecycledatthesametemporalfrequencyasthemovinggratings.Participantsviewedtwoexamplesofthemovinggratingsineachdirectionfor6seach,to-getherwiththe“xationsquareandtone.Participantsweretoldtotrytoattendtothesize,color,andspeedofthestripes,sothatlateryoucanpicturethemclearlyevenwhenthescreenisblank.ŽAtthebeginningofeachofthe8imageryblocks,participantswerere-familiarizedwiththegratingsbyagainviewingtwoexamplesofgrat-ingsineachdirectioninrandomorder(6seach).Partici-pantswerenottoldwhichdirectionofmotiontheywouldneedtoimagineuntilafterthere-familiarization.Thispreventedthemfrombeingabletoselectivelyattendexamplegratingsmovinginthedirectionofimageryforthesubsequentblock.Eachtrialconsistedofaperiodofimageryadaptationfollowedbyviewingarealmoving-dotteststimulus.Theimageryadaptationperiodwas60sinthe“rsttrialofeachblockand6sineachsubsequenttrial.Afterviewingthemoving-dotteststimulusparticipantsindicateditsdirec-tionwithakeypress.Withineachblockoftrials,thedirec-tionofimageryandwhethertheeyeswereopenorclosedwasthesame.Foreachdirectionofimageryadaptation,thereweretwoeyes-openblocksandtwoeyes-closedblocks,inrandomorder.4.DecayofimageryadaptationExperiment3wasconductedtoassesswhetherafteref-fectsfrommentalimagerydecayoveraperiodofafewseconds,asdoaftereffectsfromvisualmotion(Keck&Pentz,1977).ThisexperimentwasidenticaltoExperiment2excepttherewasavariabledelay(1,4,or13s)betweenwhenparticipantswerecuedtoopentheireyesfollowingimageryandwhenthetestprobeappeared;therewasnoeyes-opencondition;therewere8dotcoherencevaluestestedinsteadof12;andthereweretwoblocksoftrialsin-steadof8,witheachblockconsistingof48insteadof24trials(2directionsforthetestprobe8coherenceval-3delaydurations).J.Winaweretal./Cognition114(2010)276…284 5.RealmotionadaptationInExperiments4and5,wetestedadaptationtorealvi-sualmotion.TheprocedureandstimuliwereidenticaltothoseinExperiments1and2(up/downandin/outmotionadaptation,respectively)exceptthatratherthanbeingin-structedtoimaginemotionduringadaptation,participantsweresimplyinstructedto“xateontheactualmovinggrat-ing;examplesofthemovinggratingswerenotshownatthebeginningofeachblockbecauseparticipantsdidnotneedtoimaginethegrating;therewerefourblocksoftri-alsinsteadofeightbecausetherewerenoeyes-closedblocks;andtherewasnoauditorytimingguide.6.ResultsImageryofmotionproducedmotionaftereffects.Imag-iningmotionupwardmadeparticipantsmorelikelytoseethetestdotsasmovingdownward,comparedtoimaginingmotiondownward.Likewise,imaginingmotionoutwardmadeparticipantsmorelikelytoseethetestdotsasmov-inginward.Theseeffectswerefoundfromimagerybothwitheyesclosedandwitheyesopen.Moreover,theeffectsofimageryadaptationweakenedwhenadelaywasintro-ducedbetweenadaptationandtest,ashasbeenfoundforperceptualmotionadaptation(Keck&Pentz,1977Weinferthatvisualmotionimageryinvolvessomeofthesamedirectional-selectivemotionprocessingcircuitsthatareusedforperceptionofmotion.Below,themotionafter-effectsarequanti“edandcomparedtoaftereffectsfromperceptionofrealmotion.6.1.AnalysisFig.2showsthepopulationmotionsensitivitycurvesfollowingoppositedirectionsofimageryadaptation.Ineachplot,theverticalseparationbetweenthecurvesindi-cateshowdifferentlythesamephysicalstimuluswasjudgedfollowingimageryinoppositedirections.Thehori-zontalseparationindicatestheamountbywhichtwostim-ulithatwerejudgedbyparticipantsasthesame(followingadaptationindifferentdirections)wereinfactphysicallydifferent.Hadtherebeennoeffectofimagerythetwocurveswouldoverlap.Ifparticipantshadansweredbasedonanassociation(e.g.,withabiastorespondupwardsfol-lowingupwardsimagery)thenthedifferencebetweenthecurveswouldhavebeenintheoppositedirectionthanwhatweobserved.Themotionaftereffectswerequanti“edasthesepara-tionbetweenthepairedfunctions,estimatedbylogistic Fig.1.Experimentalprocedure.Priortoeachimageryblockparticipantsviewedfourexamplesofmovinggratings.Thedirectionofimagery(upvs.downorinvs.out)andwhethertheeyeswereopenorclosedwerethesamethroughouttheblock.Eachtrialwithinablockconsistedofmotionimageryfollowedbyateststimulus.Animagerytrialbeganwiththeappearanceofastaticgratingandasmallarrowindicatingthedirectionofmotionimageryforthatblock.Thegratingandarrowthenfaded.Oneyes-opentrials,theparticipantthenimaginedmotion(60sforthe“rsttrialofablock,6sforeachsubsequenttop-upŽadaptationtrial)onascreenthatwasblankexceptforthe“xationtimingguide.Duringtheeyes-closedblocks,participantswereinstructedtoclosetheireyeseachtimethestaticgratingfadedandimaginemotionwhilelisteningtotheauditorytimingguide.Attheendofeachimageryperiod,thetonestoppedcycling,andwasfollowedbyapauseandabeep,cueingparticipantstoopentheireyesandattendtothemoving-dotteststimulus.Theteststimulusappeared1safterthebeepcueingtheendoftheimageryperiod.ForExperiment3,the“xationperiodbetweenimaginedmotionandteststimulusvariedinduration.Forcontrolexperimentswithrealmotion,thegratingdidnotfade;participantswereinstructedtopassivelyviewthemovinggratingwhile“xatingthecentralsquare.J.Winaweretal./Cognition114(2010)276…284 “tstothepopulationdata(Fig.2;seeAppendixAformod-el“ts).Theaftereffectswerefurtherquanti“edonindividualparticipants.Alogisticregressionwas“ttoeachpartici-pantsdata.Thisprovidedforeachparticipantanesti-mateoftheseparationbetweenthetwocurves(upvs.downorinwardvs.outward)foreacheyecondition(openandclosed).Wecodedthisvalueaspositiveiftheseparationbetweenthecurveswasinthedirectionpredictedbyanaftereffectandnegativeifitwasintheoppositedirection.Wetestedthisvalueagainstanullhypothesisofno-shiftbytwo-tailed,one-sample(Experiments3…5),orbyanalysisofvarianceusingeyecondition(openorclosed)asarepeatedmeasure(Exper-iments1and2).6.2.ImageryadaptationAsmallbuthighlysigni“cantaftereffectfromimagerywasobserved,evidentinthepopulationdata“ts(Fig.2andtheindividualdata“ts(Fig.3).Theindividualdatafromup/downimagery(Experiment1)showedasepara-tionbetweenthemotionresponsefunctionsof0.15±0.05(mean±sem)unitsofnormalizedcoherence(1,28)=9.3;=0.005).Therewasnosigni“cantdiffer-encebetweenthesizeoftheeffectfromimagerywiththeeyesclosed(0.19±0.06)vs.eyesopen(0.11±0.05)(1,28)=2.5,=0.12).In/outimagery(Experiment2)alsoyieldedsigni“cantmotionaftereffects,withaseparationbetweenthefunc-tionsforinwardvs.outwardimageryof0.08±0.03unitsofnormalizedcoherence((1,27)=6.8;=0.015).Aswiththeup/downimageryexperiment,themotionaftereffectfromimagerywiththeeyesclosed(0.10±0.04)wasnotsigni“cantlydifferentfromtheeffectwiththeeyesopen(0.06±0.03)((1,27)=2.3;=0.145).Notethatifthedataforindividualparticipantsarerep-lottedwiththeactualcoherencevaluesoftheteststimuliinsteadofnormalizedunits,thentheshapeofthecurvesforeachisexactlythesame;onlythescaleofthex-axischanges.Reanalysiswiththeseactualcoherencevaluesyieldsthesamepatternofresults.Thesizeoftheafteref-fectsintermsofactualcoherencewas4.7±1.4%(1,28)=10.9;=0.003)fortheup/downimageryexper-imentand2.9±1.4%((1,27)=4.3;=0.049)forthein-ward/outwardimageryexperiment. Fig.2.Aftereffectsfollowingmotionimagery.Theseparationbetweenpopulationmotionsensitivitycurvesindicatesthatparticipantsweremorelikelytoperceivemotionoftheteststimulusinthedirectionoppositeimagery,evidenceforamotionaftereffectfrommotionimagery.Datapointsrepresentthemeanfrequencyofrespondingupward(Experiment1,upperpanels)orinward(Experiment2,lowerpanels)eitherwiththeeyesclosed(left)oreyesopen(right).ErrorbarsareoneSEMbyparticipant.Thex-axisisthemotioncoherenceinnormalizedunits.Positivenumbersarearbitrarilyassignedtoupwardorinwardmotion.Thecurvesarelogisticregressions“ttedtothepopulationdata(seeAppendixA).Theseparationbetweenthe“ttedfunctions,inunitsofnormalizedcoherence,is0.13,0.06,0.14,and0.08forup/downimagerywitheyesopen,up/downimagerywitheyesclosed,in/outimagerywitheyesopen,andin/outimagerywitheyesclosed,respectively.Foreachoftheseparameterestimates,thelowerboundwasabove0:0.10,0.05,0.05,and0.03,respectively(95%con“denceintervals).J.Winaweretal./Cognition114(2010)276…284 6.3.DecayofadaptationfromimageryExperiment3showedthatabriefdelaybetweenimag-eryandtestprobeweakenedtheadaptationeffect(Fig.3right).A1-sdelay,identicaltothatinthe“rsttwoexper-iments,producedareliablemotionaftereffect(0.11±0.5unitsofnormalizedcoherence),aboutequalinmagnitudetotheaftereffectinthecorrespondingconditioninthepre-viousimageryexperiment(in-out,eyesclosed,0.10±0.04).Theeffectdeclinedwithlongerdelays,(4s,0.06±0.06;13s,0.01±0.06),withasigni“cantdifferencebetweentheshortestandlongestdelay((26)=1.73;=0.047,one-tailed,paired6.4.AdaptationtorealvisualmotionAsexpected,viewingrealvisualmotionledtoarobustmotionaftereffect(Fig.4).Forupwardanddownwardmo-tion,theseparationbetweenthetwofunctionsfollowingoppositedirectionsofadaptation,basedon“tstoindivid-ualparticipants,was0.73±0.25unitsofnormalizedcoher-ence((23)=2.92,0.008,two-tailedone-sampleor21±6.4%intermsoftheun-normalizedcoherence(23)=3.44,0.002).Adaptationtoinwardoroutwardmotionalsoledtoalargemotionaftereffect:aseparationbetweencurvesof0.37±0.04unitsofnormalizedcoher-ence((6)=9.02,=0.0001).Theseeffectswereabout3…biggerthanthosefoundfromimagery.7.DiscussionInthesestudiesparticipantsimaginedmotioninapar-ticulardirectionandwerethenaskedtojudgethedirec-tionofmotionofamoving-dotsstimulus.Wefoundthatimaginingmotionproducedamotionaftereffect.Forexample,afterimaginingmotiondown,participantsweremorelikelytoperceiveasetofmovingdotsasmovingup(oppositethedirectionofimagery).Theseresultsdem- Fig.3.Aftereffectssummarizedbymodel“tstoindividualparticipantdata.Upperleft:Separationbetweenpairedmotionsensitivitycurves,eitherwiththeeyesclosedoropenduringimagery(mean±sem).Textlabelsindicatethesizeoftheshiftinunitsofun-normalizedmotioncoherence.Positivevaluesrepresentashiftconsistentwithamotionaftereffect(e.g.,increasedlikelihoodofrespondingupwardafterdownwardimagery).Up/downandin/outimagerybothledtosigni“cantmotionaftereffects,withnumericallylargershiftswiththeeyesclosedthanopen.Upperright:Theeffectofdelaybetweentheimageryperiodandtheonsetofthetestprobe.Asigni“cantaftereffectisfoundwitha1-sdelay,replicatingthepreviousimageryexperiment(thirdbar,upperleft).Theeffectisweakerwithlongerdelays.Lowerpanel:Scatterplotdepictingeachparticipantspairednullpointsfollowingimagery.Eachdatapointrepresentstheamountofmotioncoherenceatwhichthepairedmotionsensitivityfunctionscrossthe50%point,eitherforup/downimagery(circles)orin/outimagery(s).PointsabovetheidentitylinecorrespondtoaseparationbetweenmotionsensitivitycurvesinthedirectionpredictedbyanJ.Winaweretal./Cognition114(2010)276…284 onstrateforthe“rsttimethatimageryofmotionrecruitsdirection-selectiveneuralmechanismsthatarealsousedforperceivingrealmotion.Themotionaftereffectsweob-servedfromimageryweresmallerthanthosefromrealmotion,consistentwithreportsshowinglessactivationofsensorycorticalareasfrommotionimagerythanfromperceptionofthesamestimuli(Goebeletal.,1998;Gross-man&Blake,2001).Ourresultsshowthatvisualimageryofmotioncanaffecttheperceptionofsubsequentphysicalmotionstimuli,andthatperceptionandimageryofmotionrelyonshareddirection-selectiveneuralmechanisms.Twoimportantalternativeexplanationscanberuledoutbasedonthepatternofresults.First,themotionafter-effectobtainedfromin/outimagerydiscountsthepossibil-itythattheeffectswereportareduetoeyemovementsandnotimagery,suchasthemotionaftereffectscausedbypursuiteyemovementsintheabsenceofmotionper-ception(Chaudhuri,1990,1991;Freeman,Sumnall,&Snowden,2003).Second,themotionaftereffectfromimag-erywiththeeyesclosedarguesagainstvisualattentionasthesourceoftheeffects,suchasthemotionaftereffectsobservedfromattentionalampli“cationofrealmotionsig-nals(Alais&Blake,1999)orattentionaltrackingofmovingstimuli(Culham,Verstraten,Ashida,&Cavanagh,2000Althoughonemightpositthatparticipantsattendedtostimulus,thisexplanationstillrequiresthatimageryrecruitsdirection-selectivemotionmechanismsintheabsenceofsensoryinput,inaccordwithourinter-pretation.Attentionalmechanismsforastimulusorfea-ture,bycontrast,presumablyoperateonrepresentationsthataredeliveredbyfeed-forwardinputs.Moreover,tworesultssuggestthattheaftereffectswerenotduetoasimplecognitivebias.First,abriefdelayafterimageryadaptationweakenedtheeffect,ashasbeenfoundforadaptationtorealmotion(Keck&Pentz,1977).Becausethedirectionofimagerywasalwaysthesamewithinablockof48trials,itisunlikelythatparticipantsrelyingonanexplicitresponsebiasstrategywouldsimplyforgetwhichwaytorespondaftersuchabriefdelay.Aknowl-edge-basedbiasmightbeexpectedtobepresentthrough-outtheblock.Secondly,debrie“ngfollowingExperiment1suggeststhatparticipantswerenotsigni“cantlyin”uencedbytheirknowledgeofmotionaftereffectsorexpectationsofthe Fig.4.Motionaftereffectsfollowingadaptationtorealvisualmotion,eitherupwardordownward(topleft)orinwardandoutward(topright)Positivevaluesonthe-axisindicateupwardmotionorinwardmotion.Theaftereffectisabout3…4largerthanthatobservedfollowingimageryadaptation(bottom).Theimageryresultsinthebarschartarereplottedfromtheeyes-closedconditionofExperiment1(up/down)and2(in/out).J.Winaweretal./Cognition114(2010)276…284 experiment.Theparticipantswereaskedtwoquestionsattheendoftheexperiment:HaveyoueverheardoftheMo-tionAftereffectbefore,andAfterviewingupwardmotion,wouldyouexpectastaticimagetoappeartomoveupor.TheanswerstothesequestionswerenotpredictiveoftheobservedMAEs:participantswhoreportedhavingheard(=7)vs.nothavingheard(=17)oftheMAEshowedshiftsof0.13±0.03vs.0.10±0.01inthemotionresponsecurvesfollowingoppositedirectionsofimagery(22)=.631;=0.53,two-tailed,unpaired-test),poolingacrosseyes-openandeyes-closedconditions.The17par-ticipantswhohadnotheardofthemotionaftereffectwereevenlydividedintheirresponsesastowhetherastaticim-agewouldappeartomoveintheopposite(=8)vs.thesame(=8)directionofpriorviewingofmotion;onepar-ticipantrespondedthatitwouldnotappeartomoveatall.Ourresultsareconsistentwithpriorpsychophysicalstudiesonspatialimagery(Ishai&Sagi,1995)andtheimageryandinferenceofmotion.Gildenandcolleaguesdemonstratedthatadaptationtorealvisualmotionaffectedimageryofmotion,theconverseofourexperi-ments.Importantly,however,theauthorsattributedtheirresultstoaneffectofmotionadaptationontheimaginedofastimulus,notaneffectofmotionadaptationonmotionimagery.Thisexplanationwouldnotapplytoourexperimentalparadigm,sincetheimaginedstimulioccupiedthesamelocationregardlessofthedirectionofmotion.Ourresultsarealsoconsistentwithaprior“ndingthatimaginingmotioncanleadtotheillusionofrollvec-tion,wherebyspatialjudgmentsarealteredbyimageryofrotation(Mast,Berthoz,&Kosslyn,2001).Previouslyweobservedthatpassiveviewingofphotographsthatde-pictmotioncanleadtoamotionaftereffect(etal.,2008).Ourcurrentstudiesaddtothesebyshowingforthe“rsttimethatmotionimagery,intheabsenceofmotionperceptionandevenintheabsenceofanyvisualinput,canrecruitandadaptdirectionalmotionmecha-nisms.Moregenerally,ourresultsindicatethattop-downsignalsinthebraincanselectivelyexertspeci“ceffectsonappropriatesubpopulationsofsensoryneurons.AcknowledgementsWethankGordonBower,NancyKanwisher,JoshWall-man,andNathanWitthoftforreadinganearlierversionofthismanuscript.WethankJesseCartonandTarazLeeforassistanceinrunningexperiments.AppendixA.MeasurementofmotionresponseA.1.DisplayanddotsstimulususedParticipantssatinaquiet,darkroom,approximately40cmfromaniMacCRTmonitor(resolution:1024pixels(2619.5cm),refreshrate:75Hz).Theteststimulusfortheup/downimageryandrealmo-tionadaptationexperimentsconsistedof100dotsinarectangularwindowwhoselengthandwidthwere33%oftheentiredisplay(approximately12by9degreesofvisualangle).Oneachframeasubsetofthedotswereselectedtomovecoherentlyupordown.Allotherdotsdisappearedandrandomlyreappearedatanylocationwithinthetestwindow.Anewsetofdotswasre-selectedforcoherentmovementoneachframe.ThislimitedlifetimeŽproce-durewasusedsothatthetrajectoryofsingledotscouldnotbefollowedthroughoutatrial.Eachtesttrialconsistedof25framesdisplayedfor40mseach(1stotal).Dotdis-placementforcoherentmotionwasperframe.Fortheinward/outwardexperiments,theteststimulusconsistedof200dots,100oneachsideof“xation.Onagi-ventrialthecoherentcomponentofthedotsmotionwashorizontaleitherinwardoroutward(towardsorawayfromtheverticalmidline).Thestimuluswasotherwiseidenticaltotheteststimulususedfortheup/downBaselinemotiondiscriminationtaskTodetermineanappropriaterangeofmotioncoher-encesforeachparticipant,allparticipants“rstcompletedabaselinemotiondiscriminationtask.Moving-dotdisplayswerepresentedin1-strialswithupto65%ofdotsmovingcoherentlyprecedingup/downexperimentsandupto100%precedingin/outexperiments.Thecoherencevaluesproducing99%correctresponsesineachdirectionbasedonlogistic“tstotheresponseswereusedtodeterminethemaximumtestcoherencefortheadaptationphaseoftheexperiments.Asthisvaluedependedonthepartici-pantsperformanceonthebaselinetask,itdifferedacrossparticipants(36±17%and35±12%,mean±SD,fortheup/downandin-outimageryexperiments,respectively).Wede“nedthisvalueas1unitofnormalizedcoherenceinordertomakecomparisonsacrossparticipants.Fortheup-downexperiments,coherencevaluesofone-halfandone-quarterofthisvaluewereusedasteststimuli,giving6teststimuliforeachparticipant(±1,±0.5,and±0.25normalizedŽcoherence.)Forthein-outexperiments,thenormalizedcoherencevaluesweresampledmore“nely:±1,±0.67,±0.44,±0.29,±0.19,±0.13,±0.08,±0.05,±0.03,±0.02,±0.01,and0.A.3.Logisticregression“tstomotionresponsefunctionsA.3.1.Population“tsTheresponsestomoving-dotteststimuliweremodeledasalogisticregression.Themodel“ttotheaggregatedata(allparticipantsinthepopulation)foragivenpairofopposingadaptingconditionsusedthefollowingequation,“twithamaximumlikelihoodalgorithm,Inthisequation,isthemotionsignalinnormalizedunitsofcoherence(withpositivevaluesassignedtoeitherupwardorinwardmotionandnegativevaluesassignedtodownwardoroutwardmotion).)istheprobabilitythattheparticipantindicatesupward(orinward)motion.thedirectionofmotionimageryorrealmotionprecedingthedottrial(+1or1),and,andarefreeparame-J.Winaweretal./Cognition114(2010)276…284 ters.Thefreeparameterscorrespondto(i),thedeviationfrom0%and100%withwhichresponsesasymptoted,(ii),,anoverallbiastorespondinaparticulardirection,(iii),themotionsensitivityorsteepnessofthefunction,andtheeffectofadaptation.Dividingtheseparationbetweenthepairedcurvesinunitsofcoher-ence.Thusthisvalueindicateshowmuchmotionmustbeaddedtoastimulusinoneadaptationconditiontomakeitperceptuallyequivalenttothesamestimulusintheoppo-siteadaptationcondition.The95%con“denceintervalforeachparameterestimatewasdeterminedbybootstrap-ping:1000simulateddatasetsweregeneratedforeachpairofadaptationconditionsbasedontheactualpopula-tionmeanresponses,eachdatasetwas“ttedbyEq.the1000parameterestimateswererankordered,andthe975thand25thvaluesweretakenasthecon“denceA.3.2.Individual“tsThemodel“tsforindividualparticipantsusedasimilarequation,butbecausetherewaslessdataforindividualparticipantsthanforthewholepopulation,fewerfreeparameterswereused:...ÞðThismodeldiffersfromthepopulationmodelinthattherewasnoparametertomodeltheasymptoteand,fortheimageryexperiments,theeffectsofadaptationweremodeledinasingleequationforallconditions.ThusforExperiments1and2,thereweretwoadaptationterms,onefortheeyes-closedcondition()andonefortheeyes-opencondition().ForExperiment3,therewerethreeadaptationtermsforthethreedelayconditions().Fortherealmotionadaptationexperiments,onlyoneadaptationparameterwasmodeled().Inallexperi-ments,themotionsensitivity()andglobalbias()wereestimatedonlyonceperparticipant,whereasforthegroupdataintheimageryexperimentstheseparameterswere“tseparatelyforeachpairofadaptingconditions(eyesopenandeyesclosed).Aswiththepopulation“ts,dividingyieldstheseparationbetweenthepairedcurvesinunitsofcoherence.Themeanofthisvalueacrossparticipantswastakenastheeffectofadaptationforeachpairofadaptationconditions.A.4.ParticipantsexcludedfromanalysisFifteenparticipantswereexcludedfromanalysisforfailingtoperformwellonthemotiondiscriminationtask.Nineparticipants(2of33doingup/downimagery,2of31doingin/outimagery,2of30intheimagery-delayexperiment,and3of31viewingup/downrealmotion)didnotshowasigni“canteffectofmotioncoherence.Fortheseparticipants,theprobabilityofanupŽorinŽre-sponsedidnotsigni“cantlyincreasewithincreasedcoher-enceinthatdirectionintheteststimulus.Speci“cally,theparameterestimatedformotioncoherenceinalogisticregression“twaslessthanthestandarderrorofthesameparameterestimate.Sixotherparticipants,(1of33doingup/downimagery,1of31doingin/outimagery,1of30intheimagery-delayexperiment,and3of31doingup/downrealmotion),performedpoorlyinthebaselinemo-tiondiscriminationtasksuchthatcurve“tsyieldedaunitofnormalizedcoherenceasvalues�100%actualcoherence.Theseparticipantswereexcludedfromanalysis.Alais,D.,&Blake,R.(1999).Neuralstrengthofvisualattentiongaugedbymotionadaptation.NatureNeuroscience,2(11),1015…1018.Barlow,H.B.,&Hill,R.M.(1963).Evidenceforaphysiologicalexplanationofwaterfallphenomenonand“guralafter-effects.Nature,200Beauchamp,M.S.,Cox,R.W.,&DeYoe,E.A.(1997).GradedeffectsofspatialandfeaturalattentiononhumanareaMTandassociatedmotionprocessingareas.JournalofNeurophysiology,78(1),516…520.Blake,R.,&Hiris,E.(1993).AnothermeansformeasuringthemotionVisionResearch,33(11),1589…1592.Chaudhuri,A.(1990).AmotionillusiongeneratedbyafternystagmusNeuroscienceLetters,118(1),91…95.Chaudhuri,A.(1991).Eyemovementsandthemotionaftereffect:Alternativestotheinducedmotionhypothesis.VisionResearch,(9),1639…1645.Corbetta,M.,Miezin,F.M.,Dobmeyer,S.,Shulman,G.L.,&Petersen,S.E.(1991).Selectiveanddividedattentionduringvisualdiscriminationsofshape,color,andspeed:FunctionalanatomybypositronemissionJournalofNeuroscience,11(8),2383…2402.Culham,J.C.,Verstraten,F.A.,Ashida,H.,&Cavanagh,P.(2000).Independentaftereffectsofattentionandmotion.Neuron,28Freeman,T.C.A.,Sumnall,J.H.,&Snowden,R.J.(2003).Theextra-retinalmotionaftereffect.JournalofVision,3(11),771…779.Gilden,D.,Blake,R.,&Hurst,G.(1995).Neuraladaptationofimaginaryvisualmotion.CognitivePsychology,28(1),1…16.Goebel,R.,Khorram-Sefat,D.,Muckli,L.,Hacker,H.,&Singer,W.(1998).Theconstructivenatureofvision:DirectevidencefromfunctionalmagneticresonanceimagingstudiesofapparentmotionandmotionEuropeanJournalofNeuroscience,10(5),1563…1573.Grossman,E.D.,&Blake,R.(2001).Brainactivityevokedbyinvertedandimaginedbiologicalmotion.VisionResearch,41(10…11),1475…1482.Hiris,E.,&Blake,R.(1992).AnotherperspectiveonthevisualmotionProceedingsoftheNationalAcademyofSciences,89Huk,A.C.,Ress,D.,&Heeger,D.J.(2001).Neuronalbasisofthemotionaftereffectreconsidered.Neuron,32(1),161…172.Ishai,A.,&Sagi,D.(1995).CommonmechanismsofvisualimageryandScience,268(5218),1772…1774.Keck,M.J.,&Pentz,B.(1977).RecoveryfromadaptationtomovingPerception,6(6),719…725.Kohn,A.,&Movshon,J.A.(2003).NeuronaladaptationtovisualmotioninareaMTofthemacaque.Neuron,39(4),681…691.Kosslyn,S.M.,Pascual-Leone,A.,Felician,O.,Camposano,S.,Keenan,J.P.,Thompson,W.L.,etal.(1999).Theroleofarea17invisualimagery:ConvergentevidencefromPETandrTMS.Science,284Kosslyn,S.M.,Thompson,W.L.,&Alpert,N.M.(1997).Neuralsystemssharedbyvisualimageryandvisualperception:Apositronemissiontomographystudy.Neuroimage,6(4),320…334.Kosslyn,S.M.,Thompson,W.L.,Kim,I.J.,&Alpert,N.M.(1995).TopographicalrepresentationsofmentalimagesinprimaryvisualNature,378(6556),496…498.Mast,F.W.,Berthoz,A.,&Kosslyn,S.M.(2001).Mentalimageryofvisualmotionmodi“estheperceptionofroll-vectionstimulation.Perception,30(8),945…957.Mather,G.,Verstraten,F.,&Anstis,S.M.(1998).Themotionaftereffect:Amodernperspective.Cambridge,Mass:MITPress.Newsome,W.T.,&Pare,E.B.(1988).Aselectiveimpairmentofmotionperceptionfollowinglesionsofthemiddletemporalvisualarea(MT).Neuroscience,8(6),2201…2211.OCraven,K.M.,&Kanwisher,N.(2000).Mentalimageryoffacesandplacesactivatescorrespondingstiimulus-speci“cbrainregions.JournalofCognitiveNeuroscience,12(6),1013…1023.OCraven,K.M.,Rosen,B.R.,Kwong,K.K.,Treisman,A.,&Savoy,R.L.(1997).VoluntaryattentionmodulatesfMRIactivityinhumanMT-Neuron,18(4),591…598.J.Winaweretal./Cognition114(2010)276…284 Perky,C.W.(1910).Anexperimentalstudyofimagination.JournalofPsychology,21,422…452.Petersen,S.E.,Baker,J.F.,&Allman,J.M.(1985).Direction-speci“cadaptationinareaMToftheowlmonkey.BrainResearch,346Pylyshyn,Z.W.(2002).Mentalimagery:Insearchofatheory.BehavioralandBrainSciences,25(2),157…182(discussion182…237).Saenz,M.,Buracas,G.T.,&Boynton,G.M.(2002).Globaleffectsoffeature-basedattentioninhumanvisualcortex.NatureNeuroscience,(7),631…632.Slotnick,S.D.,Thompson,W.L.,&Kosslyn,S.M.(2005).VisualmentalimageryinducesretinotopicallyorganizedactivationofearlyvisualCerebralCortexVanWezel,R.J.,&Britten,K.H.(2002).MotionadaptationinareaMT.JournalofNeurophysiology,88(6),3469…3476.Winawer,J.,Huk,A.C.,&Boroditsky,L.(2008).Amotionaftereffectfromstillphotographsdepictingmotion.PsychologicalScience,19Wohlgemuth,A.(1911).Ontheafter-effectofseenmovement.Cambridge:UniversityPress.J.Winaweretal./Cognition114(2010)276…284