Present self, past self and close-other : event-related potential study of face and name detection

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Biological Psychology

j o u r n a l h o m e p a g e :w w w . e l s e v i e r . c o m / l o c a t e / b i o p s y c h o

Present self, past self and close-other: Event-related potential study of face and name detection

Ilona Kotlewska, Anna Nowicka

^∗

NenckiInstituteofExperimentalBiology,DepartmentofNeurophysiology,LaboratoryofPsychophysiology,3PasteurStreet,02-093Warsaw,Poland

a r t i c l e i n f o

Articlehistory:

Received26January2015

Receivedinrevisedform27July2015 Accepted28July2015

Availableonline30July2015

Keywords:

Name Face P300 Presentself Pastself Close-other

a b s t r a c t

Agrowingbodyofevidencesuggeststhatinformationregardingthepastselfandotherpeopleispro- cessedsimilarly.However,thereisnotmuchevidencesupportingthisnotionattheneurallevel.Inthis event-relatedpotential(ERP)studyweexaminedprocessingofone’sownmaritalandfamilyname(i.e., presentandpastself-name,respectively)andimagesofpresentandpastself-faceincomparisonto namesandfacesofothers(theclose-other,famousandunknownperson).AmplitudesofP300(alate ERPcomponentassociatedwithattention,emotion,andautobiographicalmemory)toself-faceandself- name,eitherpresentorpast,wasenhancedincomparisontofamousandunknownfacesandnames.

Nodifferences,however,wereobservedbetweenthepastandpresentself-namesaswellasbetween pastandpresentself-faces.Moreover,P300amplitudetothepastself-facewasenhancedintheright hemisphereincomparisontotheclose-other’sface,whereasP300amplitudestothepastself-nameand theclose-other’snamedidnotdiffer.Thus,ourresultsindicatedthatinformationrelatedtonon-physical aspectsofthepastselfwereprocessedsimilarlytotheclose-other.

1. Introduction

Thesenseofself-continuityseemstobeanessentialaspectof thehumanconsciousness(Gallagher,2000; Moranet al.,2006;

Morin,2006).Itisrelated toautobiographicalmemoryand itis basedontheabilitytoconsolidatedifferentandtemporallysepa- ratedpiecesofself-relatedinformationintoaonecoherentwhole (Conway,2005;McAdams,2001).Lifebringssubstantialchanges (bothphysical,e.g.,weightgain/lossandsituational,e.g.,startofa newjob)astimepasses,andthesechangesimplysigniﬁcantmodi- ﬁcationsofself-relatedinformation.Astheselfcontinuallyevolves, theself-conceptisupdatedinordertoaccountforthesealterations (Demo,1992;Deutschetal.,1988).

Agrowingbodyofevidenceindicatesthatpeopledistancethem- selvesfromtheirpastselfwhentheyperceiveself-changes,even regardingtheirpastselfas‘anotherperson’(Libby&Eibach,2002;

Pronin&Ross,2006;Wilson&Ross,2003).Thisisespeciallythecase whenrecallingpastbehaviorsandsituationsthatarediscrepant withthepresentself-concept.Onsuchoccasionspeoplefrequently adoptathird-personperspective,asiflookingnotatthemselves

∗ Correspondingauthor.Fax:+48228225342.

E-mailaddresses:i.kotlewska@nencki.gov.pl(I.Kotlewska), a.nowicka@nencki.gov.pl(A.Nowicka).

butatsomeoneelse(Libby&Eibach,2002).Additionally,people askedtoformimagesofpasteventsinwhichtheyparticipated oftenclaimtoseethemfromtheperspectiveofanexternalobserver (e.g.,Cohen&Gunz,2002).Also,attributionsmadeaboutthepast selfresembleattributionsmadeaboutothersratherthanattribu- tionsregardingthepresentself(Pronin&Ross,2006).Allinall, itseemsthatfollowingnumerouspersonalchangespeoplemay processinformationabouttheirpastselvesasinformationabout others.

Thetopicofchangestotheselfacrosstimehasbeenthefocusof manyresearchgroups.However,onlyafewattemptshavebeen recentlymadetounraveltheneuralbasisoftemporally-distant selves. For both the present and distant time-periods, previ- ousstudiesinvestigatedself-reﬂection(D’Argembeauetal.,2008, 2010;Luoetal.,2010),subjectivementaltime(Arzy,Collette,Ionta, Fornari,&Blanke,2009),andself-facerecognition(Apps,Tajadura- Jimenez,Turley,&Tsakiris,2012;Butler,Mattingley,Cunnington,

&Suddendorf,2013).

Inoneoftheearlieststudiesinthisfield,evaluationsofpsycho- logicalcharacteristicsofone’sownpersonandtheother(friend) wereconductedforboththepresentandapasttimeperiodswhile functionalmagneticresonanceimaging(fMRI)datawerecollected (D’Argembeauetal.,2008).Thedegreeofactivityincorticalmidline structures(CMS)wassignificantlyinfluencedbyboththetarget of reflectionand periodof time. Theventral anddorsal medial http://dx.doi.org/10.1016/j.biopsycho.2015.07.015

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prefrontalcortex(MPFC)andtheposteriorcingulatecortexwere more recruited when reflecting onthe present self than when reflectingonthepastselforwhenreflectingontheclosefriend, withthosetwo conditionsshowing nodifferences.In afollow- upstudy,theMPFC activitywashigher whenreflecting onthe presentselfthanwhenreflectingonbothpastandfutureselves (D’Argembeauetal.,2010).The effectsoftemporal perspective, however,werenotmodulatedbythetraitvalence.

Interestingly,this impactofemotional valenceontheneural basis of self-evaluation across time wasreported in an event- relatedpotentials(ERP)study(Luoetal.,2010).Inthatstudy,for bothpresentandpastselves,theprocessofevaluationofnegative traitsincomparisontopositive traits,resultedinhigherampli- tudesof a late positive ERP component (so-calledlate positive complex—LPC)in the650–800mstimewindow.Thebehavioral ﬁndingsofthisstudyindicatedthatforeachtemporalself,par- ticipantshadconsistentlylessnegativeandmorepositiveviewsof themselves,inlinewithstudiesonself-enhancement(Leary,2007;

Sedikides&Gregg,2008).

Arzyetal.(2009),inturn,investigatedsubjectivementaltime, i.e.,‘self-projection’ofoneselftodifferenttimepointsnotonlywith respecttoone’slifeeventsbutalsowithrespecttoone’sfacesfrom differentpastandfuturetime-points.Participantswereaskedto imaginethemselvesatoneofthreedifferentself-locationsintime:

‘now’(thepresenttime),‘past’(8yearsinthepast)or‘future’(8 yearsinthefuture).Faceimagesoftheparticipantaswellas a famousperson(GeorgeClooney)weremodiﬁedinsuchawaythat theyrepresentedtheparticipant’sandClooney’sfaceappearingas 4,12and20yearsyounger(pastfaces)orolder(futurefaces).In onepartoftheirexperiment,facesoftheparticipantorofClooney wereshownandparticipantswereaskedtoindicatewhetherthe presentedfacerepresentedtheparticipant’s/Clooney’sappearance before(relative-past)orafter(relative-future)theimaginedself- locationin time. Similarly, in theotherpartof theexperiment participantswereaskedtoindicatewhetherthepresentedevent fromtheirpersonallifeorworldhistoryoccurredbeforeorafterthe currentlyimaginedself-locationintime.Analysisforpast,present, andfutureself-locationsrevealedanetworkcommonforbothfaces andevents,consistingoftherightanteromedialtemporallobe,pos- teriorparietalcortexbilaterally,leftinferiorfrontalcortex,insula bilaterally,andrighttemporo-parietaljunction.Inasubsetofthese brainregions,thepercentoffMRIsignalchangeshowedhigheracti- vationforthepastandfutureself-locationsthanforthepresent self-location.

Finally, several studies reportedchanges in brain correlates associatedwithprocessing of presentand past self-faces(Apps etal.,2012;Butleretal.,2013).Neuralcircuitsinvolvedintherecog- nitionofchildhoodandcurrent(adult)faceswereexaminedusing fMRI(Appsetal.,2012).Participantsviewedimagesofeithertheir ownpresentfacemorphedwiththefaceofafamiliarotherortheir childhoodfacemorphedwiththechildhoodfaceofafamiliarother.

Morphedimagesofadultself-facesactivateddifferentneuralnet- worksthanmorphedimagesofself-facesinchildhood.Speciﬁcally, activityintheinferioroccipitalgyrus,thesuperiorparietallobule andtheinferiortemporalgyrusvariedwiththeamountofcurrent selfinanimagewhereasactivityinthehippocampus,theposte- riorcingulategyrus,thetemporo-parietaljunctionandtheinferior parietallobulevariedwiththeamountofchildhoodselfinanimage (Appsetal.,2012).

Inarecentstudy,ERPresponsestopastandpresentimagesof participants’faceswereinvestigatedinagroupofdizygotictwins (Butleretal.,2013).Photographsweretakenwhentheywere5–15, 16–25and26–45yearsold.Theformertwotimeperiodsreferredto thepast(more-distantandless-distantpast,respectively)whereas thelattercorrespondedtothepresent,i.e.,theperiodoftimein whichtheexperiments weredone. Controlstimuliconsisted of

theparticipant’stwinandunfamiliarother’sphotographsoffaces, comingfromthesametimeperiods.Theresultsofthisstudyclearly showedthatamplitudesofN400(alatenegativeERPcomponentin the400–600mstimewindow)differedasafunctionoftimeperiod, butonlyfor imagesofselfand notfortwin. Processingofboth thepresentself-faceandtheless-distant-pastself-faceresultedin greaterN400thanidentiﬁcationoftheself-faceintheearlyperiod oflife.

Allinall,someoftheaforementionedstudiesreporteddiffer- encesbetweenneuralunderpinningsofthepastandpresentselves (Arzyetal.,2009;D’Argembeauetal.,2008;D’Argembeauetal., 2010)whereasothersdidnot(Luoetal.,2010).Intwocases,such differenceswerefoundforthecurrentselfcomparedtothevery- distant-pastself,i.e.,theselfinchildhood(Appsetal.,2012;Butler etal.,2013)buttheywereabsentifthecurrentselfwascompared totheless-distant-pastself,i.e.,theselfinadolescenceandearly adulthood(Butleretal.,2013).

Asfarasrelationbetweenthepastselfandtheotheriscon- cerned,notmuchevidenceexists—attheneurallevel—supporting thenotionthatthepastselfisprocessedliketheother.Onlyone studyreportedthatneuralcircuitsassociatedwithevaluationof psychologicaltraitsinrespecttothepastselfandtheother(friend) didnotdiffer(D’Argembeauetal.,2008).Otherstudieseitherdid notinclude‘theother’asacontrolcondition(D’Argembeauetal., 2010;Luoetal.,2010),ordidnotcomparethepastselfvs.theother (Appsetal.,2012;Butleretal.,2013).Therefore,onemaywonder whethertheneuralunderpinningsassociatedwiththepastselfand theclose-other(friend,mother,etc.)aresimilarwhenprocessing ofinformationotherthanpersonalitytraitsisrequired.

Forthisreason,inthecurrentstudyERPresponsestopresent andpastself-facesandself-nameswerecomparedtoERPresponses tofacesandnamesoftheclose-other,famous,andunknownpeo- ple.Thereisnodoubtthatone’sownpresentandpastfacesare appropriatetocapturetime-relatedchangesintheself(Butleretal., 2013).However,weproposethatone’sownnameisalsosuitable torefertothepastandpresentselvesifithasbeenchangedat somepointinlife.Examplesofsuchchangesincludeprotectedwit- nessesandwomenwhotaketheirhusband’snameaftermarriage.

Itisworthnotingthatthelatterismuchmorecommonthanthe former.Thusonlymarriedwomenwhovoluntarilychangedtheir namesparticipatedinourstudy,andsubject’sfamilynamewas consideredtobethepastself-name,whereasthesubject’smarital namewasthepresentself-name.Incontrasttopreviousstudieson pastandpresentself-faceprocessingthatusedaseriesofpastself- faceimages(Arzyetal.,2009;Butleretal.,2013),onlyoneimage ofthepastself-facewaspresentedtoparticipants.Itwastakenjust beforethename-change(i.e.,beforemarriage)andtheimageofthe presentself-facewastakenjustbeforeparticipationinourstudy.

SimilarlytoourpreviousERPstudiesonnameand faceprocessing, we used here written full names (Cygan, Tacikowski, Chojnicka,Ostaszewski,&Nowicka,2014;Tacikowski&Nowicka, 2010;Tacikowskietal.,2011).Thus,thesetwodifferenttypesof stimuliwerepresentedwithinthesame(visual)modality.Thiswas donetoreduce—asmuchaspossible—thenumberoffactorsthat couldpotentiallydifferentiateERPstonamesandfaces.

ERPstudieswithintheframework oftheperson-recognition models(Bruce&Young,1986;Burtonetal.,1990;Valentine,Moore,

&Brédart,1995)identiﬁed severalcorrelatesof faceand name processing. The occipito-temporal N170 (a negative deﬂection occurringaround170msafterthestimulusonset)wasshowntobe sensitivetofaceinversion,butitwasratherunaffectedbythefamil- iarityofaface(e.g.,Bentin,Allison,Puce,Perez,&McCarthy,1996).

N170isoftenlargerfornamesthanforfacesinthelefthemisphere (Schweinberger, Ramsay, & Kaufmann, 2006; Tacikowski et al., 2011)andlargerforfacesthanfornamesintherighthemisphere (Rossion &Jacques,2008).Moreover,N170is ratherunaffected

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by the familiarity of names and faces (Eimer, 2000; Rossion etal.,2000;Schweinbergeretal.,2004)and/orprimingmanipu- lations(Pfütze,Sommer,&Schweinberger,2002;Schweinberger, Kaufmann,Moratti,Keil,&Burton,2007;Schweinberger,Pickering, Burton, & Kaufmann, 2002; Schweinberger,Pickering, Jentzsch, Burton,&Kaufmann2002).Asaconsequence,N170istypically associatedwithstimulus-categorydiscrimination.Itisnowwidely agreedthatN170representstheanalysisofstructuralinformation offaces(Bentin&Deouell,2000;Carbonetal.,2005;Eimer,2000;

Herzmannetal.,2004;Schweinberger,Pickering,Jentzschetal., 2002)orwordformanalysisincaseofnames(Bentin,Mouchetant- Rostaing,Giard,Echallier,&Pernier,1999).

UnlikeN170,asubsequenttemporal-parietalN250(arelatively smallnegative deﬂection occurringaround250ms afterstimu- luspresentation)seemstoreﬂect theactivationoffamiliarface or familiar name representations stored in long-term memory (Schweinberger, Pickering, Jentzsch et al., 2002). N250 ampli- tude is: (1) larger for familiar than for unfamiliar names and faces (2) larger for perceptually primed than unprimed names and faces, and (3) unaffected by semantic priming (Sommer, Komoss,&Schweinberger,1997;Pfützeetal.,2002;Pickering&

Schweinberger,2003; Schweinberger,Pickering, Jentzsch et al., 2002;Tacikowskietal.,2011).Asaresult,N250wassuggestedto reﬂecttheprocessofmatchingtheinputnameorfacetorepresen- tationsofnamesandfacesstoredinlong-termmemory(Miyakoshi, Nomura,&Ohira,2007).

Lastly,P300(apositive componentoccurringaround 300ms afterthestimulusonset,withitsmaximumovercentral-parietal scalp sites) has been related to multiple cognitive functions, includingcontextupdating,allocationofattentionalresourcesand associativememoryprocesses(forreviewseePolich,2007).How- ever,in thecontext oftheperson-recognition modelP300was associatedmainlywithaccesstosemanticinformationaboutthe personwhosenameorfaceisbeingrecognized.Supportforthis claim comesfrom observations that P300 is modulated bythe familiarityofnamesandfacesanddoesnotdifferentiatebetween names and faces (Bentin & Deouell, 2000; Eimer, 2000; Paller etal.,2000;Schweinberger,1996;Cyganetal.,2014;Tacikowski&

Nowicka,2010;Tacikowskietal.,2011).

ERP studies prove strong modulation of brain activity by one’sownname andface.The self-preferenceeffect wasfound for ERP components described within the person recognition model—N170, N250, and P300 as well as for two additional components—P200andN400.Forsomeofthosecomponentssuch effectwaspresentforbothnamesandfaces,whereasforothers—for onetypeofstimulusonly.Themostconsistentﬁndingsreferto P300.P300amplitudeislargerforone’sownnamethanforother names(Berlad&Pratt,1995;Cyganetal.,2014;Fanetal.,2013;

Folmer &Yingling, 1997; Gray et al.,2004; Holeckova, Fischer, Giard, Delpuech, &Morlet, 2006; Müller &Kutas, 1996; Perrin etal.,2005;Scottetal.,2005;Sui,Zhu,&Han,2006;Tacikowski

&Nowicka,2010;Tacikowskietal.,2011;Zhaoetal.,2009).This effectseemstobetask-independentsinceitwasobservedeven duringpassivelisteningtotheone’sownname(Holeckovaetal., 2008).Preferentialresponsestoownname,asrevealedbyelevated P300,werepresenteveninstatesofreducedconsciousness,such asvegetativestateorminimallyconsciousstates(Dietal.,2007;

Perrinetal.,2006;Staffenetal.,2006).

Theprocessingofone’sownfacealsoresultedinmuchhigher P300amplitudethanprocessingof otherfaces(e.g.,Tacikowski

&Nowicka, 2010; Tacikowskiet al., 2011; Tanakaet al., 2006) and, interestingly,this effect wasnot inﬂuenced byattentional manipulationandtask-relevance,indicatinganautomaticprocess ofself-facerecognition(Cyganetal.,2014;Gunjietal.,2009;Sui etal.,2006).P300isalsosigniﬁcantlyenhancedwhenprocessing ofothertypesofself-relatedinformation,e.g.,hometown,phone

number,mother’sﬁrstname,bank,birthdate,initialsetc.(Gray etal.,2004).

ApartfromP300,differentprocessingofself-vs.othernames andself-vs.otherfaceswasreportedforN170.Hölleretal.(2011) reportedpreferentialprocessingwhenpresentingone’sownname aurally,reﬂected in higher amplitudes of N170.Analogousevi- denceforvisualpresentationofone’sownnameismissing,but similarearlyeffects (atthelevel of N170)were foundforself- faceprocessing(Keyes,Brady,Reilly,&Foxe,2010).However,in the case of P200(frontal-central component withapproximate latencyof200ms)self-preferentialeffectswerefoundfornames only.Hu,Wu,andFu(2011)reportedthatprocessingofsemantic self-relatedinformation—participant’sfullname,dateofbirth,and hometown—wasrelatedtolargerP200responsesthanstranger’s fullnameandself-irrelevantdateandplace.Fanetal.,(2013)found thatP200waslargertothenameoftheparticipantthantothe nameofparticipant’sfatherandtothenamesoffamouspeople.

AmplitudesofN250component,inturn,werelargerforboththe self-name(Zhaoetal.,2009)andfortheself-face(Keyesetal.,2010;

Tanakaetal.,2006)thantoothernamesandfaces,respectively.

Self-faceprocessingresultedalsoresultedinenhancedamplitudes ofN400incomparisontothefaceoftwin(Butleretal.,2013)or a friend’sface (Keyes et al.,2010), aswellasin comparison to unfamiliarfaces.

Previousstudiesshowedthattheprocessingofone’sownname and/orimagesofone’sownfaceispreferentialandthatthisprefer- encemayoccurattheearly(N170,P200,N250)andlate(P300, N400) stages of information processing. Based onour previous studieswithpresentationofnamesandfaces(Cyganetal.,2014;

Tacikowski&Nowicka,2010;Tacikowskietal.,2011;Tacikowski etal.,2014),weexpectedthatinthecurrentstudyeffectsrelated tothepresentandpastselvesaswellastothecloseotherwould emergeinP300.However,theothercandidatewasP200,although self-relatedeffectsforthatcomponenthavesofarinvolvedone’s ownnameonlyandweredeﬁnitelynotsooftenreported.

Preferential processing of self-related information has often been attributed to the highly arousing and attention-grabbing nature of self-related information (e.g., Huet al., 2011).If this isthecase,theself-preferenceeffectshouldbeobservedevenif anyintentionaldiscriminationbetweenpresentedstimuliisnot required,forinstanceinstudieswithasimpledetectionofstimuli.

Thissuppositionwassupportedbyourpreviousstudyonnameand faceprocessinginwhichsuchataskwasusedwithfavorableresults (Cyganetal.,2014).Speciﬁcally,detectionofone’sownnameand one’sownfaceresultedinincreasedamplitudesofP300incom- parisontoallothernamesand faces(i.e.,close-other’s,famous, unknown).However,itisamatterofdebatewhetheritisthecase forself-relatedinformationreferringtothepast,i.e.,whetherauto- matic attentionallocationmay alsobepreferential forthepast self-nameandthepast-self-face.Thuswedecidedtouseadetection taskinconjunctionwithERPanalysis.

Taking all of the aforementioned findings into account, the hypothesisreferringtothepresentandpastself-namesandself- faceswasbasedon:(i)Butler’setal.,(2013)study,reportingalack ofsignificantERPdifferencesbetweenthepresentself-faceandpast self-facefromadolescence/adulthood;(ii)ourpreviousERPstudies onnameandfaceprocessingshowingnodifferencesbetweenone’s own(present)nameandone’sown(present)face(Cyganetal., 2014;Tacikowski&Nowicka,2010;Tacikowskietal.,2011).Thus weexpectedthatButleretal.’sfindingswouldbe‘extended’for presentandpastself-names.

Asfarastherelationbetweenthepastselfandtheclose-other wasconcernedwehypothesizedthat itmight beinﬂuencedby thetypeofinformation(namesvs.faces).BasedonD’Argembeau etal.’sstudy(2008)thatreportedlackofdifferencesfor‘psycholog- ical’(‘non-physical’)aspectsofthepastselfandfriendweexpected

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similarneuralunderpinningsforthepastself-nameandtheclose- other’snamesasnamesarestimulireferringtothe‘non-physical’

aspectsofaperson.However,inthecaseoffaces,reﬂectingphysi- calaspectsofpastselfandclose-other,thereweretwoalternative hypotheses:(i) thetwo conditions would result in similarERP responsesifanyinformationrelatedtothepastselfwasprocessed likeinformationrelatedtotheclose-other;or(ii)pastself-faceand close-otherfacewouldbeassociatedwithdifferentERPresponsesif similaritiesbetweenprocessingofinformationrelatedtothepast- selfandtheclose-otherwererestrictedonlytothenon-physical aspectsofthepastselfandclose-other.

2. Methods 2.1. Participants

Twenty ﬁve healthy female volunteers with normal or corrected-to-normalvision participatedin thestudy.Onlymar- riedwomenwhoacceptedtheirspouse’slastnamewererecruited.

Three subjects were excluded from analyses due to excessive movement artifacts. Participants’ ages varied from 24 to 60 (mean±standard deviation: 35.7±8.7). The required minimal length of marriage was three years and varied from 3 to 37 (9.64±8.86).Noneof thesubjectshad ahistory ofneurological diseases.HandednesswascontrolledwiththeEdinburghInven- tory(Oldﬁeld,1971).Twentythreeparticipantswereright-handed, oneleft-handed,andoneambidextrous.Informedwrittenconsent wasobtainedfromeach participantprior tothestudy.Allsub- jectswerepaidfortheirparticipation.Theexperimentalprotocol wasapprovedbythelocalEthicsCommittee(UniversityofSocial SciencesandHumanities,Warsaw,Poland).

2.2. Stimuli

Stimuliconsisted ofﬁrst andlast names(whichwill stillbe referredtoas‘names’forthesake ofsimplicity) andpicturesof facespresented visually on a computerscreen against a black background.Namesweredisplayedwithwhitelettersandfaces wererenderedgrayscale. Faceswereextractedfromtheirback- groundsusingAdobe PhotoshopCS5^® software(AdobeSystems Incorporated),renderingonlytheface,earsandhairvisible.Picture luminancewasmatchedtothecolorstatisticsofasinglepicture.

Thesizeofthestimulirangedfrom2×3^◦to2×6^◦fornamesand from5×4^◦ to5×6^◦ forpictures.Allpictures wereresizedtoa heightof198pixels.

Fivedifferentcategoriesofstimuliwereapplied:(1)subject’s maritalnameandfaceatpresent,(2)subject’sfamilynameand faceinthepast.Asthecontrolconditionsnameandfaceof (3) a close-other,(4) a famous person, e.g., a celebrity, and (5) an unknownperson.Priortothestudyparticipantswererequested todeliverthreephotographspresenting:anactualimageofself- face,animageoftheirfacetakenjustbeforemarriage,andarecent pictureofafemaleclose-other.Onerestrictionwasmadeonthe choiceoftheclose-other:ﬁrstandlastnames(pastorpresent)of thesubjectandtheclose-otherhadtodifferinordertoavoidasso- ciationsofthelatterwitheitherpastorpresentself-name.Forthis reasonnoneofthesubjectschoseone’sownmother,withmost choosingtheirbestfriend,sister(twocases),orcousin(onecase).

The averagelength of acquaintance was15±9.27 years. Mean lengthofnames(in numberof letters) wasasfollows: present self—14.95±2.73,pastself—15.5±3.54,close-other—13.86±2.25, famous—14.91±2.72,andunknown—14.93±2.69.Namelengths didnotdiffer signiﬁcantlybetweencategories (presentvs. past p>0.9;presentvs.close-otherp>0.9;presentvs.famousp=0.88;

presentvs.unknownp>0.9;pastvs.close-otherp>0.9;pastvs.

famousp=0.60;pastvs.unknownp>0.9;close-othervs.famous p>0.9; close-other vs. unknown p>0.9; famous vs. unknown p=0.16).AllofthemwereofPolishorigin.

A set of stimuli was individually tailored for each subject.

Famousandunknownpersonswereselectedtomatchthelengthof ﬁrstandlastname,ageandappearanceofthesubject.Thephotosof famousandunknownpeopleweredownloadedfromtheInternet.

Priortotheexperimenteachparticipantconﬁrmedfamiliaritywith thefamouspersonanddeniedacquaintancewiththeunknownone inherstimuliset.

2.3. Experimentalprocedure

Stimuli were displayed centrally on a 19-inch LCD monitor (NECMultiSync1990Fx).Stimulipresentationwasdesignedusing Presentation^® software (Neurobehavioral Systems, Albany, CA, USA).Participantswereseatedcomfortablyinanacousticallyand electricallyshieldedroomatadistanceof60cmfromthemonitor.

Asimpledetectiontaskwasapplied:theparticipantsrespondedto eachstimulusasquicklyaspossiblebypressingthesamebuttonon aCedrusResponsepad(RB-830,SanPedro,USA).Theinstructions wereintroducedtwice:ﬁrstverballybytheexperimenterandthen displayedonthemonitorbeforetheexperimentstarted.Subjects hadtoconﬁrmtheirunderstandingoftheinstructionbypressing theappropriatebutton.

Eachtrialconsistedofthefollowingsequenceofevents:pre- sentationofaﬁxationcross(white“+”againstblackbackground) for1000ms,thetargetitemdisplayedforamaximumof3000ms unlessthesubjectreactsearlier,andablankscreenfor1000ms.

Responsescauseddisappearanceofthetargetitem.Thesequence ofstimulipresentationwaspseudo-randomizedsothatnomore thanthreestimuliofthesametypeorthesameconditionwere presentedconsecutively.Stimulusofeachtypeandcategorywas presented30times.Theexperimentlastedapproximately15min.

Aftertheexperimentalpartofthetasksubjectswereaskedto ﬁlloutanIdentiﬁcationForm,whichconsistedoffourquestions regardingthesubject’sattitudetopresentandpastnameandface.

Theparticipantswereaskedtoratetheirlevelofidentiﬁcationwith present/pastnameandpresent/pastfaceona7-pointscalewhere 1correspondedto‘Idonotidentifymyselfwiththisname/photo’

and7to‘Istronglyidentifymyselfwiththisname/photo’.

2.4. EEGrecordings

EEG was continuously recorded from 62 scalp sites using a 128-channelampliﬁer (QuickAmp, Brain Products,Enschede, Netherlands)andBrainVisionRecorder^®software(BrainProducts, Gilching,Germany).Ag-AgClelectrodesweremountedonanelas- ticcap(ActiCAP,Munich,Germany)andpositionedaccordingto theextended10–20system.Electrodeimpedancewaskeptbelow 5k.TheEEGsignalwasrecordedagainstanaverageofallchan- nelscalculatedbytheampliﬁerhardware.Thesamplingratewas 500Hz.

2.5. Behavioraldataanalysis

Responseswithin200–2000msafterthestimulusonsetwere scoredascorrect.Meanreactiontimes(RTs)wereanalysedusing repeated measures ANOVA with ‘type of stimuli’ (two levels:

names,faces) and‘condition’ (ﬁvelevels:presentself,pastself, close-other, famous, unknown) as within-subject factors. The Identiﬁcation Form scale ratingswere analysed using repeated measuresANOVA withtwo within-subject factors,each at two levels:‘typeofstimuli’(names,faces)and‘time’(past,present).

Alleffectswithmorethanonedegreeoffreedominthenumer- ator were adjusted for violations of sphericity (Greenhouse &

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Fig.1. Levelofidentificationwiththepresentandpastname/face(percentageofresponseschosenintheIdentificationForm).Response1indicatedcompletelackof identificationwithagivenstimuluswhereasresponse7—verystrongidentification.Asillustrated,thevastmajorityofparticipantsdeclaredsignificantlyhigheridentification withtheirpresentfaceandnamethanthepastones.

Geisser, 1959). Bonferroni correction for multiple comparisons wereappliedtopost-hocanalyses.AllanalysesweredoneinSPSS (AdvancedModel).

2.6. ERPanalysis

Off-line analysis of the EEG data was performed using BrainVisionAnalyzer^® software (Brain Products, Gilching, Germany). The ﬁrst step of analysis was to re-reference EEG datatothemeansignalfromearlobes.Subsequently,Butterworth Zero Phase ﬁlters were applied: low cutoff—0.1Hz, 12dB/oct;

highcutoff—20Hz,12dB/oct;andnotchﬁlter—50Hz.Correction forocularartifactswasperformedwithuseoftheIndependent Components Analysis, ICA(Bell & Sejnowski, 1995).After each datasetwasdecomposedintomaximallystatisticallyindependent components,theelementsrepresentingeyeblinkswererejected based on a visual inspection of the component’s map (Jung etal.,2001).Theremainingcomponentsweremultipliedusingthe reducedcomponent-mixingmatrixandback-projectedtothedata, resultinginasetofocular-artifact-freeEEG.Thenthecontinuous EEGsignal wassegmented into epochs extendingfrom 200ms beforeto1000msafter thestimulusonset (baseline correction from−200to0ms).Next,theAnalyzer’ssemi-automaticartifact rejectiontoolwasusedforrejectingtrialsexceedingthefollowing terms:themaximumpermittedvoltagesteppersamplingpoint was50␮V,themaximumpermittedabsolutedifferencebetween twovaluesinthesegmentwas200␮V,andthelowestpermitted activityinthe100msinterval was0.5␮V.Finally, theEEGseg- mentswereaveragedforeachcategoryofstimulitocreateERPfor asinglesubject.

Overall98%oftrialspassedtheartifactrejectionprocedurefor bothtypesofstimuli.Thedetailedrangeofacceptedsegmentsfor eachcondition(fornamesandfaces,respectively)wasasfollows:

98%and97%forpresentself,98%and98%forpastself,98%and98%

forclose-other,98%and97%forfamous,98%and97%forunknown.

Themeanofvaluesateachtimepointwithinacertaininterval wasusedtoassessamplitudesofourERPcomponentsofinterest.

Thismethodislessaffectedbypossiblelowsignal-to-noiseratio

thanthepeakmeasuresmethods(Luck,2005).Basedonthevisual inspectionofgrand-averageERPsandbasedontheexistinglitera- ture,thefollowingtime-windowswereused:150–250ms(P200) and350–550ms(P300).

WefocusedonscalpregionsinwhichtheabovementionedERP componentshadtheirmaximumamplitudes(seethetopography mapsinFigs.2–4)andlocalizationsreportedinpreviousstudies (e.g.,Herzmann&Sommer,2007;Huetal.,2011;Liuetal.,2013;

Mu&Han,2010;Schweinbergeretal.,2006;Tacikowski&Nowicka, 2010;Tacikowskietal.,2011).P200wasanalyzedinthefrontal- centralregion(F3,F4,FC3,FC4,FCz,Fz),andP300inthecentral- parietalregion(C3,C4,CP3,CP4,CPz,P3,P4,andPz).

Amplitudes wereanalyzed using repeatedmeasures ANOVA with‘typeofstimuli’(twolevels:names,faces),‘condition’(ﬁve levels:presentself,pastself,close-other,famous,unknown)and electrodesite(P200—sixlevels:F3,F4,FC3,FC4,FCz,Fz;P300—eight levels: C3,C4,CP3, CP4,CPz,P3, P4, Pz)as within-subject factors. All effects withmore than one degree of freedom in the numeratorwereadjustedforviolationsofsphericity(Greenhouse

&Geisser,1959).Bonferronicorrectionformultiplecomparisons wereappliedtopost-hocanalyses.AllanalysesweredoneinSPSS (AdvancedModel).

3. Results

3.1. Behavioralresults

StatisticalanalysisofRTsdidnotshowanysigniﬁcanteffects.

Mean RTs (±SD) for each experimental condition were as fol- lows: present name—488±244ms, past name—465±242ms, close-other’s name—461±219ms, famous name—467±237ms, unknownname—482±251ms, present face—492±292ms,past face—495±295ms, close-other’s face—491±287ms, famous face—475±245ms,andunknownface—486±260ms.

ANOVA carried on responses from the Identiﬁcation Form revealeda main effectoftime factor (F(1,21)=26.72,p<0.001,

p2=0.56), indicating a signiﬁcantly higher level of identi- ﬁcation with stimuli referring to the present self (present

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Fig.2.GrandaverageERPsfornames(A)andfaces(B).Greencirclesindicateelec- trodelocations(F3,FC3,Fz,FCz,F4,FC4)atwhichmeanamplitudesofP200were analyzed(C).Topographicmapsofthevoltageintheanalyzedtimeperiod,sepa- ratelyfornamesandfaces(D).

name—6.59±0.67; present face—6.27±1.2) than with stimuli referring to the past self (past name—5.09±1.48; past face—4.82±1.84). Type of stimuli factor and its interaction withtimefactorwereinsigniﬁcant(seeFig.1).

Pearson’scorrelationcoefficientsdidnotshowsignificantcor- relationsbetweentheresponsesgivenintheIdentificationForm andtheparticipants’ageorlengthofmarriage:identificationwith currentself-namexage,r=0.136,p=0.546;identificationwithcur- rentself-namexwedlock,r=0.07,p=0.755;identificationwithpast self-namexage,r=−0.133,p=0.557;identificationwithpastself- namexwedlock,r=−0.227,p=0.310;identificationwithpresent self-facexage,r=0.185,p=0.410;identificationwithpresentself- facexwedlock,r=0.184,p=0.412;identificationwithpastself-face xage,r=−0.191,p=0.394,identificationwithpastself-facexwedlock,r=−0.378,p=0.078.

3.2. Electrophysiologicalresults

3.2.1. P200

ANOVAonP200amplitudesrevealedasigniﬁcantmaineffect ofelectrodesite(F(2,50)=8.64,p<0.001,p2=0.29).P200ampli- tudesatelectrodesiteslocatedinthemidlinewerehigherthan

P200amplitudesinthelefthemisphere(Fzvs.F3,p=0.002;Fzvs.

FC3,p=0.019;FCzvs.F3,p=0.004;FCzvs.FC3,p=0.004).Theinter- action:typeofstimuli xelectrodesite alsoreachedthelevelof statisticalsigniﬁcance(F(3,63)=2.90, p<0.042,p2=0.12).Post- hoctestsshowedthatP200tonameswasenhancedonlyatFzin comparisontoF3(p=0.047)whereasP200tofaceswasincreased atelectrodesitesinthemidline(Fzvs.F3,p=0.001;Fzvs.FC3, p=0.022;FCzvs.F3,p=0.001)andintherighthemisphere(FC4vs.

F3,p=0.037).Allothereffectsandinteractionswereinsigniﬁcant.

Fig.2illustratesthoseresults.

3.2.2. P300

ANOVAonP300amplitudesrevealedasigniﬁcantmaineffectof typeofstimulus(F(1,21)=18.23,p<0.001,p2=0.46).Ingeneral, allfaceselicitedhigheramplitudesthannames(seeFigs.3and4).

There was also a main effect of electrode site (F(3, 60)=6.57, p<0.001,p2=0.24)whichwasassociatedwithsignificantlyhigher P300 amplitudes in the midline than in the left hemisphere (Pz>C3,p=0.008;Pz>CP3,p=0.023;CPz>C3,p=0.001;CP4>C3, p=0.048).Inaddition,post-hocstoasignificanttwo-wayinterac- tionbetweentypeofstimuliandelectrodesite (F(3,62)=13.67, p<0.001,p2=0.39)indicatedthatdifferencesinP300amplitudes betweenelectrodesiteswereinsignificantinthecaseof names (allps>0.2)buttheyweresignificantinthecaseoffaces(C3<CPz, p=0.001;C3<Pz,p=0.001;C3<CP3,p=0.002;C3<CP4,p=0.015;

C3<P3, p=0.001; C3<P4, p=0.017; CP3<Pz, p=0.001; C4<Pz, p=0.026;CP3<Pz,p=0.001;CP3<P3,p=0.004).

Taking intoaccount thegoalsof ourstudy,themain points of interest were the condition factor (i.e., present self, past self,close-other,famous,unknown)anditsinteractions.ANOVA yielded a signiﬁcantconditionfactor (F(3, 55)=13.63,p<0.001,

p2=0.39).Post-hoccomparisonsshowedthatP300amplitudesin thepresentselfcondition(i.e.,thepresentself-name,thepresent self-face)weresigniﬁcantlyhigherthanP300amplitudesinthe close-other(p=0.009),famous(p=0.001)andunknown(p=0.004) conditions(i.e.,close-other’s,famousandunknownnames/faces).

However,thepresentandpastconditions(i.e.,presentandpast self-name/self-face)wereassociatedwithsimilarP300amplitudes (p>0.9).Thepastselfcondition,inturn,resultedinenhancedP300 incomparisontothefamous(p=0.004)andunknown(p=0.002) conditions.Thedifferencebetweenthepastselfandtheclose-other conditiondidnotreachthelevelofstatisticalsigniﬁcance(p=0.06).

Importantly,thesigniﬁcantinteractionbetweencondition,type of stimuli and electrode (F(28,588)=1.69, p=0.016,p2=0.07), indicated thattheeffects foundforsomeconditions differedin respectofthetypeofstimuli(namesvs.faces)and/orlocationof electrode.Post-hoccomparisonsshowednodifferencesbetween P300amplitudetothepresentself-nameand pastself-nameat eitheroftheanalysedelectrode sites(CPz,Pz,C3,C4,CP3,CP4, P3,allps>0.9;P4,p=0.823).Similarly,nodifferenceswerefound betweenP300amplitudestothepresentself-faceandpastself-face ateitheroftheanalysedelectrodesites(CPz,Pz,C3,C4,CP3,CP4, P3,allps>0.9;P4,p=0.765).

Asfarasthepastselfandtheclose-other’snamesand faces areconcernedpost-hoctestindicatedthatP300amplitudesasso- ciatedwiththepastself-namedidnotdifferfromtheclose-other’s nameatanyelectrodesite(allps>0.9).Inthecaseoffaces,however,differencebetweenthepastself-faceandclose-other’sface waspresentintherighthemisphereatcentro-parietalsites(CP4, p=0.050; P4, p=0.053). A similar weaktrend was observed at themidlineelectrodes(CPz,p=0.091;Pz,p=0.088).Nodifference betweenP300amplitudestothepastfaceandclose-other’sface wasfoundatelectrodesitesinthelefthemisphere(C3,p>0.9;CP3, p=0.378;P3,p=0.237).

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Fig.3. GrandaverageERPsfornames(A).Bluecirclesindicateelectrodelocations(C3,CP3,P3,CPz,Pz,C4,CP4,P4)atwhichmeanamplitudesofP300wereanalyzed.

Analyzedinterval(350–550ms)ismarkedwithgraycolorintheleftupperimageforreference.Topographicmapsofthevoltagedistributionintheanalyzedtimeperiod, foreachconditionseparately(B).

4. Discussion

Onefundamental featureofthehumanconsciousexperience isasenseofselfthatpersistsacrosstime.ThedesignofourERP studyenabled us toshed furtherlight onthe neuralprocesses thatunderpinprocessingofinformationrelatedtothepresentself, thepastself,andothers.Wehypothesizedthatprocessingofthe presentself-name/faceandpastself-name/facewouldnotdiffer, resultinginsimilarERPresponses.Inaddition,weexpectedthat relationbetweenERPresponsestothepastselfandtheclose-other mightbeinﬂuenced bythetype ofinformation, i.e.,whetherit referredtophysical(faces)ornon-physical(names)aspectsofper- son.Speciﬁcally,wehypothesizedthatthepastself-nameandthe close-other’snamewouldbesimilarlyprocessedwhereasitwould rather notbethecase for faces.Generally,resultsofourstudy supportedthosehypotheses.

Signiﬁcanteffects involvingcategory ofstimuli(i.e.,whether theyreferredtopresent self,pastself,close-other,famousperson,unknownperson)andtypeofstimuli(namesvs.faces)were observedforP300.However,noeffectswerefoundforP200.Inpre- viousstudies,enhancedP200toself-relatedcueswasreportedin

thecaseofevaluationofpersonalitytraitsinrelationtotheself andothers(Liuetal.,2013;Mu&Han,2010)orinthecaseoflying abouttheselfandothers(Huetal.,2011).Moreover,P200differ- encesbetweentheself-namevs.othernameswerefoundwhen overtrecognitionofnameswasrequired(Tacikowskietal.,2014) orwhenanoddballtaskwasused(Fanetal.,2013).Itseemsthat theabsenceofP200effectsinthecurrent studymaybea con- sequenceofthesubstantialmethodologicaldifferences.Insome oftheaforementionedstudiesrathercomplexcognitiveprocesses wereinvestigated(processoflying,reﬂectingontheselfandthe other,recognitionofnames).Inaddition,theallocationofattention mighthavebeenvaryingdependingontheexperimentalproce- dure. Forinstance, inFan etal.’sstudynameswereusedasan infrequenttargetstimuliamongotherwordsthathadtobeignored.

Incontrast,inourstudy,thesimpledetectiontaskdidnotrequire anyintentionaldiscriminationbetweenpresentedstimuli,engaged attentionautomatically,andevokedthesamemotorreaction(i.e., pressingthesamebutton)foreachstimulus.

TheresultsforP300amplitudesshowedthatthepresentself condition(one’sownpresentname,presentself-face)wasassoci- atedwithhigheramplitudesofP300thanfamous,andunfamiliar

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Fig.4.GrandaverageERPsforfaces(A).Bluecirclesindicateelectrodelocations(C3,CP3,P3,CPz,Pz,C4,CP4,P4)atwhichmeanamplitudesofP300wereanalyzed.Analyzed interval(350–550ms)ismarkedwithgraycolorintheleftupperimageforreference.Topographicmapsofthevoltagedistributionintheanalyzedtimeperiod,foreach conditionseparately(B).

namesandfaces.Theseﬁndingslayinlinewithnumerousstudies showingsuchaself-preferenceeffect(Berlad&Pratt,1995;Cygan etal.,2014;Fanetal.,2013;Folmer&Yingling,1997;Grayetal., 2004;Holeckovaetal.,2006;Müller&Kutas,1996;Perrinetal., 2005;Scottetal.,2005;Suietal.,2006;Tacikowski&Nowicka, 2010;Tacikowskietal.,2011;Tanakaetal.,2006;Zhaoetal.,2009).

P300responses tothepresent self-name/facewerealsosignifi- cantlyincreasedincomparisontotheclose-other’sname/face.The issueofsimilarities/dissimilaritiesbetweentheneuralcorrelates of(current)selfandtheclose-otherisamatterofongoingdebate andexperimentalevidenceisratherinconclusive.Forinstance,no differenceswerefoundfornameswhenrecognitionwasrequired (Tacikowskietal., 2014).Ifstimulirelated totheselfwerejust detected(Cyganetal.,2014),neuraldifferencesbetweentheself andtheclose-otherwereevidentbothfornamesandfaces.Self-face identification,inturn,wasalsoassociatedwithhigheramplitudes oflateERPresponses(N400)thanthetwin-faceidentificationbut sucheffectwasabsentforearlierERPcomponents(Butleretal., 2013).In addition,reflectiononpsychological characteristicsof thepresentselfandtheclose-otherengageddifferentneuralcir- cuits(D’Argembeauetal.,2008).Thisissueneedstobefurther

investigatedinordertoﬁndthefactorsthatarecrucialandcrit- icalfortheemergenceofdifferencesbetweenthepresentselfand signiﬁcantotherattheneurallevel.

Importantly,wefoundnodifferencesbetweenP300responses associatedwithprocessingofinformationrelatedtothepresent selfandpastself,foreithernamesorfaces.Specifically,P300to thepresent self-namedidnotdifferfromP300tothepastself- name,andasimilareffectwasobservedforthepresentself-face andpastself-face.Interestingly,althoughtherewasnodifference ontheneurallevel,behavioralresultsshowedsignificantlyhigher levelsofidentificationwithstimulireferringtothepresentthan thepastself.

ThispatternofP300ﬁndingsmaybeviewedinthecontextof person-recognitionmodels(Bruce&Young,1986; Burtonetal., 1990;Valentineetal.,1995).Inthesemodels,P300isconsidered toreﬂectactivationofsemanticknowledgeaboutthepersonbeing recognized(Herzmann&Sommer,2007;Kaufmannetal.,2008;

Schweinberger,Pickering,Burtonetal.,2002;Palleretal.,2000;

Schweinbergeretal.,2006;Tacikowskietal.,2011).Althoughin thecurrentstudyconsciousrecognitionofnamesandfaceswas notrequiredandwasnotnecessarytosuccessfullyaccomplishthe

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behavioraltask(simpledetection),itmighthaveoccurredwhen participantswereviewingdifferentnamesandfaces.Thus,itcan- notbeexcludedthatsimilarP300responsestothepresentandpast selfconditionswereduetosimilarlevelsofsemanticknowledge aboutthepresentandpastselves.Inaddition,anattention-related interpretationofthiseffectmayalsobeplausiblebecauseP300has oftenbeenassociatedwithattentionalprocesses(forreviewsee:

Polich,2007).Inlinewiththis,ourP300ﬁndingsmayshowthat presentandpastself-nameaswellaspresentandpast-selffaces engagedattentionalresourcestoasimilarextent.

In the context of the temporal perspective, the difference betweenthephysical(face)andnon-physical(name)aspectsofthe selfiscrucial.Whilethechangeofnamehappenedonce(atthetime ofmarriage),changesinphysicalappearancearecontinuousdue totheprocessesofagingandotherfactors.Thusinformationabout thephysicalaspectsoftheselfareconstantlyupdated.Despitethe punctualchangeforself-nameand continuouschangesforself- face,similarpatternsofP300findingswerefoundforthepresent vs.pastself-faceandthepresentvs.pastself-name.Inaddition,this differencecouldhaveinfluencedthebehavioralresults,andsome decreaseinidentificationwithpastnameincomparisontopast facemighthavebeenexpected.However,levelsofidentification withthepastself-nameand pastself-facedidnotdiffer.More- over,thelackofP300differencesbetweenthepastself-nameand thepresentself-namecouldbeattributedtothefactthatwomen whoweremarriedformanyyearsmayviewtheirfamily(present) namesasreferringtoboththepresentandthepastselves.Although itisplausible,thevastmajorityofwomenparticipatinginourstudy usedtheirfamilynamesforamuchlongertimethantheirmarital names(theaveragewedlockwas10years,theaverageparticipant agewas36).

Previousstudiesreportedthatthetemporalperspectiveexerted inﬂuenceonneuralcorrelatesofself-facerecognitiononlywhen thecurrent(adult)selfwascomparedtothe‘childhoodself’(Apps etal.,2012;Butleretal.,2013).Suchaneffect,however,wasabsent whenthecurrentselfwascomparedtothepast,butnot-so-distant, self(Butleretal.,2013).Thelatterperfectlycorrespondstothelack ofsigniﬁcantdifferencesbetweenthepastandpresentself-facesin ourstudy.Inaddition,thelackofdifferencesbetweenlatepositive ERPresponses(LPC)tothepresentandpastselveswasobservedin thecaseofpsychologicaltraitsevaluation(Luoetal.,2010).

Incontrasttothepresentselfvs.thepast-selfcomparisonsthat showedcommoneffectsfornamesandfaces,therelationbetween thepastselfconditionandtheclose-otherconditionwasinﬂuenced bythetypeofstimuli. P300tothepastself-facewasenhanced incomparison totheclose-other’s faceintherighthemisphere whereas,P300tothepastself-nameandP300totheclose-other’s namedidnotdiffer.Itisworthnotingthatobservedneuraldif- ferencesbetweenthepastself-faceandtheclose-otherfacehave notbeenreportedinpreviousstudiesonprocessingpresentand pastself-andotherfaces(Appsetal.,2012;Butleretal.,2013).

Speciﬁcally,analysesinAppsetal.’sstudywerefocusedontest- ingwhetheractivityinanyareaofthebrainscaledparametrically withtheamountofone’sownfaceinmorphedimagesofone’sown currentfaceandthecurrentfaceofapersonallyfamiliarother,or ofone’sownchildhoodfaceandthechildhoodfaceofthesame personallyfamiliarother. Butleret al.,in turn,investigatedthe inﬂuenceoftemporalperspectivewithinagivenidentity(self,dizy- gotictwin,unfamiliarother)andnotacrossidentitiesfordifferent timeperiods(e.g.,pastselfvs.presentother).

Tothebestoftheauthors’knowledge,onlyonepreviousstudy showed similar neural underpinnings of the past self and the close-other(friend)(D’Argembeauetal.,2008).Inthatstudy,the evaluationofpsychologicalcharacteristicsofone’sownpersonin thepastandthefriendactivatedtheventralanddorsal (MPFC) andtheposteriorcingulatecortextothesameextent.Thusboth

studies—D’Argembeauetal.’s(2008)andours—provideconverging evidenceonsimilarneuralresponsestothenon-physicalaspects ofthepastselfandtheclose-otherdespitemethodologicaldiffer- ences:theexperimentaltask(reﬂectionvs.detection),measures ofbrainactivity(fMRIvs.ERP),andstimuli(personalitytraitsvs.

names).

OnemayspeculatethatsimilarlyenhancedP300responsesto thepastself-nameandtheclose-othernamemaybeattributedto thecomparableemotionalcontentofthosestimuli.Thissupposi- tionwasbasedonthenotionthatP300varieswiththeemotional valueofthestimulusandthatemotionallychargedstimuli(regard- less of their valence) produced larger P300 than neutral ones (Dietrichetal.,2001;Johnstonetal.,1986).ThepatternofP300 ﬁndingsforthepastself-nameandtheclose-othernamemaybe alsorelatedtothehypothesisaboutsharedmentalandneuralrep- resentationsofthepastselfandthesigniﬁcantother.Perceiving andappreciatingthecognitiveandemotionalsimilaritybetween oneselfandotherpeopleisanobligatorystageinthenormaldevel- opmentoftheselfthatiscrucialforsocialinteractions(Decety&

Sommerville,2003;Gopnik&Meltzoff,1994).Thisdevelopment requires“formingandcoordinatingspeciﬁcsocialrepresentations ofselfandother(...)thatextractpatternsofsimilaritybetween selfandother”(Rogers&Pennington,1991).Self-otherintegration typicallygrowsfromthedepthofsharedexperiences(Gopnik&

Meltzhoff,1994;Slotter&Gardner,2009Slotter&Gardner,2009).

Such experiences arecommonespecially ifthe‘other’ishighly familiarandemotionallyrelatedtothesubject(i.e.,thecaseofthe close-otherinourstudy).Moreover,thecognitivesigniﬁcanceof beinginaclose-relationshipwithotherpeopleisdescribedinterms ofincludingotherintotheconceptoftheself(Aron,Aron,Tudor,&

Nelson,1991;Aronetal.,2004).

In addition, it couldnot be ruled out that theP300 results reportedherewererelatedtothefrequencyofoccurrence.Inevery- daylife,self-nameandself-face,eitherpastorpresent,aswellas theclose-other’snameand wereencounteredmuch moreoften thanfamousand unknownnamesandfaces.Althoughprevious studiesshowedthattheP300componentismodulatedmoreby thesemanticthanbytheperceptual-familiarityfactor(Bentin&

Deouell, 2000; Eimer,2000; Palleret al., 2000; Schweinberger, 1996;Tacikowskietal.,2011),theissueneedsfurtherinvestiga- tion.Forinstance,Butleretal.,(2013)proposedtheexposurefactor asoneofthemajoragentsinﬂuencingtheneuralprocessingofthe self-facevs.others’faces.Thismaybevalidforfacesofownand otherrace,i.e.,theown-racebias(Meissner&Brigham,2001)and evenforfacesofownandotherages,i.e.,theown-agebias(Hills&

Lewis,2011).Followingthisidea,thedurationoftimethataperson seesthegivenstimulusdifferentiatesthefaceprocessing.Conse- quently,thedailyexposuretoownfaceacrossthelifespanshall becarefullyaddressedintheprocessesofthevisualself-vs.other recognition.

In conclusion, the processing of information (names, faces) referringtothepresentselfandthepastselfwasassociatedwith similarP300responses.However,P300tothepastself-facewas enhancedincomparisontoP300totheclose-other’sface.Thismay indicatethatphysicalaspectsofthepastselfaredifferentiatedfrom theclose-other.Incontrast,nodifferencebetweenP300responses tothepastself-nameandtheclose-other’snamesuggeststhatnon- physicalaspectsofthepastselfandtotheclose-otherareprocessed similarly.

Acknowledgments

ThisworkwasfundedbythePolishNationalScienceCentre [grant 2012/07/B/HS6/01283].Funding sources had noinvolve- mentinstudydesign,indatacollection,analysisandinterpretation,