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The inhibition of automatic imitation: a meta-analysis and synthesis offMRI studiesDarda, Kohinoor Monish; Ramsey, Richard
Neuroimage
DOI:10.1016/j.neuroimage.2019.04.059
Published: 15/08/2019
Peer reviewed version
Cyswllt i'r cyhoeddiad / Link to publication
Dyfyniad o'r fersiwn a gyhoeddwyd / Citation for published version (APA):Darda, K. M., & Ramsey, R. (2019). The inhibition of automatic imitation: a meta-analysis andsynthesis of fMRI studies. Neuroimage, 197, 320-329.https://doi.org/10.1016/j.neuroimage.2019.04.059
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09. Oct. 2020
Journal:
Title:Theinhibitionofautomaticimitation:ameta-analysisandsynthesisoffMRI
studies
KohinoorM.DardaandRichardRamsey
WalesInstituteforCognitiveNeuroscience,SchoolofPsychology,BangorUniversity,
Bangor,Gwynedd,Wales,LL572AS,UnitedKingdom
Correspondingauthor:[email protected]
Keywords:fMRI;imitation-inhibition;meta-analysis.
2
Abstract
Humanscopyotherpeoplewithouttheirconsciousawareness,abehaviourknownas
automaticimitation.Althoughautomaticimitationformsakeypartofdailysocial
interactions,wedonotcopyotherpeopleindiscriminately.Instead,wecontrolimitative
tendenciesbyprioritisingsomeactionsandinhibitingothers.Todate,neuroimaging
studiesinvestigatingthecontrolofautomaticimitationhaveproducedinconsistent
findings.Somestudiessuggestthatimitationcontrolreliesonadomain-specificneural
circuitrelatedtosocialcognition(thetheory-of-mindnetwork).Incontrast,other
studiesshowengagementofadomain-generalneuralcircuitthatisengagedduringa
diverserangeofcognitivecontroltasks(themultipledemandnetwork).Giventhe
inconsistencyofpriorfindings,inthecurrentpaperweavoidedproblemsassociated
withinterpretingindividualstudiesbyperformingameta-analysis.Todoso,weuseda
multi-levelkerneldensityanalysistoquantitativelyidentifyconsistentpatternsof
activationacrossfunctionalmagneticresonanceimagingstudiesinvestigatingthe
controlofimitation.Ourresultsshowclearandconsistentevidenceacrossstudiesthat
thecontrolofautomaticimitationisguidedbybrainregionsinthemultipledemand
networkincludingdorsolateralfrontoparietalcortex.Incontrast,therewasonlylimited
evidencethatregionsinthetheoryofmindnetworkwereengaged.Indeed,medial
prefrontalcortexshowednoconsistentengagementandrighttemporoparietaljunction
engagementmayreflectspatialratherthanimitativecontrol.Assuch,thecurrentmeta-
analysisreinforcestheroleofdomain-generalcontrolmechanismsandprovideslimited
evidenceinsupportoftheroleofdomain-specificprocessesinregulatingimitative
tendencies.Consequently,neurocognitivemodelsofimitationneedupdatingtoplace
moreemphasisondomain-generalcontrolmechanisms,aswellastoconsidermore
3
complexorganisationalstructuresofcontrol,whichmayinvolvecontributionsfrom
multiplecognitivesystems.
4
Introduction
Theinvoluntarytendencyofhumanbeingstoimitateothers’gestures,speechpatterns,
andpostures,isknownasautomaticimitation(Heyes,2011).Ithasbeensuggestedthat
suchautomaticimitativebehaviourfunctionsasa“socialglue”asitincreasespro-social
behaviour,positiverapport,feelingsofaffiliationandlikingbetweeninteracting
partners(Kavanagh&Winkielman,2016;vanBaaren,Janssen,Chartrand,&
Dijksterhuis,2009;Lakin&Chartrand,2003;Chartrand&Bargh,2009;vanBaaren,
Holland,Steenaert,VanKippenberg,2003).Giventheinfluenceofimitationon
strengtheningsocialbonds,researchershavestartedtoinvestigatethepsychological
andbiologicalmechanismsthatunderpinimitation.Forexample,overthelast20years,
researchershaveusedfunctionalmagneticresonanceimaging(fMRI)inordertobetter
understandtheneuralunderpinningsofthecontrolofautomaticimitativetendencies.
However,thesestudieshaveprovidedmixedfindingsregardingthecontributionsof
domain-generalordomain-specificneuralnetworksinimitationcontrol.Thecurrent
paper,therefore,meta-analysesfMRIstudiestodateonthecontrolofautomatic
imitationinordertoprovideacombinedquantitativeestimateoftheextantevidenceof
manyindividualstudies(Lipsey&Wilson,2001).
Inthelasttwodecades,automaticimitationhasbeenwidelystudiedwithan
attempttointerconnectdifferentdisciplineslikecognitivescience,socialpsychology,
evolutionarybiology,andcognitiveneuroscience(Prinz&Meltzoff,2002;Chartrand&
Bargh,1999;Byrne&Russon,1998).Thisconvergenceacrossmultipledisciplineshas
allowedforarangeofperspectivesonimitationtoemergeinwhichtheoryand
empiricaldatacanstrengtheneachother.Insocialpsychology,automaticimitationhas
beenstudiedinnaturalisticsocialinteractions(Chartrand&Lakin,2013).Alongwith
functioningasa“socialglue,”researchperformedinmorenaturalistsettingssuggests
5
thatimitationbehaviourisalsomoderatedbyothervariablesincluding,butnotlimited
to,personalityvariables,self-construal,goaltoaffiliateordisaffiliate,culturalandsocial
contexts,aswellasthesimilarity,familiarity,andstatusofthepersonbeingimitated
(Chartrand&Lakin,2013;Caspersetal.,2010;Duffy&Chartrand,2015).
Eventhoughautomaticimitationseemstobeanimportantbehaviourthat
facilitatessocialinteractions,wedonotalwayscopyothers’behaviours.Inmany
situations,imitationcanbemaladaptive,anditisessentialtocircumventthetendency
toautomaticallyimitate(Cross&Iacoboni,2014;Cross,Torrisi,Losin,&Iacoboni,2013;
vanSchie,vanWaterschoot,&Bekkering,2008;Newman-Norlund,vanSchie,van
Zuijlen,&Bekkering,2007).Thisneedtoregulateimitativetendenciesindicatesthe
existenceofaselectionmechanismthatinhibitsunwantedactions,andprioritises
alternatives(Brassetal.,2009).Thus,imitationcontrolcanbedividedintoatleasttwo
componentprocesses–actionrepresentationandactionselection.Weobservean
interactionpartnerandtheiractions(representation),andthenselecttheactionthat
needstobeexecuted(selection).
Incontrasttosocialpsychologyapproaches,researchersinthefieldofcognitive
psychologyandneurosciencehavegenerallyusedcomputer-basedreaction-time(RT)
measuresoftheinhibitionofautomaticimitation(Brassetal.,2000;Stürmeretal.,
2000).Oneofthemostcommonlyusedtasksinthisfieldconsistsinmakingfinger
movementswhilesimultaneouslyobservingacompatibleorincompatiblefinger
movement(Brassetal.,2000).Forexample,participantsmaybeaskedtomakeafinger
movementinresponsetoanimperativecuei.e.theyareinstructedtolifttheirindex
fingerwhentheyseeanumber‘1’onscreen,andtheirmiddlefingerwhentheyseea
number‘2.’Simultaneously,participantsalsoobserveatask-irrelevantindexormiddle
6
fingermovement,whichiscompatibleorincompatiblewiththeirownresponse.Other
variantsofthistaskincludehandopeningandclosingmovementsinsteadoffinger
movements(Pressetal.,2005;Wangetal.,2011)orpre-specifyingtheparticipant’s
responsebeforetheimperativecue(i.e.participantsareaskedtoalwayslifttheirindex
fingerwhentheyseeafingermovement;Brass,Bekkering&Prinz,2001;Heyesetal.,
2005).Inthesevariantsaswell,participantsobserveahandorfingermovementwhich
iscompatibleorincompatiblewiththeirownresponse.Irrespectiveofthetaskused,
greatercognitiveresourcesarerequiredwheninhibitingmovementsincompatibleto
one’sownresponses,thusleadingtogreaterRTs(Heyes,2011;Brass&Heyes,2005).
Thedifferencebetweentheincompatibleandcompatibleconditions(referredtoasthe
generalcompatibilityeffect)issaidtobeameasureofimitationcontrol(Heyesetal.,
2005;Heyes,2011).
Todate,anumberofneuroimagingstudieshaveinvestigatedtheneural
mechanismsofimitationcontrolusingRTparadigms.However,theevidence
demonstratingtheextenttowhichRTparadigmsofimitationcontrolengagedomain-
generalordomain-specificneuralnetworksismixed.Domain-specificprocesses
operateonparticulartypesofstimulioraspectsofcognition,whiledomain-general
processesoperateacrossarangeofstimuliandtasks(Barett,2012;Spunt&Adolphs,
2017).Oneoftheprevailingtheoriesofautomaticimitationproposesthatimitation
controlreliesonadomain-specificneuralcircuitrelatedtosocialcognition(Brassetal.,
2009).This“specialist”theoryhasgainedtractionwithevidencefrompatientand
neuroimagingdatapointingtotheengagementoftwokeycandidateregions–the
anteriormedialprefrontalcortex(mPFC)andtherighttemporoparietaljunction(rTPJ)
(Brass&Heyes,2005;Brassetal.,2009).Forexample,mPFCandrTPJhavebeen
7
engagedinhumanbrainimaginginvestigationsofimitationinhibition(Brassetal.,
2001;2005;2009;Spengleretal.,2009;Wangetal.,2011).Brassandcolleaguesfurther
proposedadissociationofrolesforthemPFCandrTPJduringimitationcontrol-the
rTPJdistinguishesbetweenself-andother-generatedactions,andthemPFCenforces
theself-generatedactionwhenfacedwithconflictfromanactionrepresentation
generatedbyanotheragent(Brassetal.,2009).Inaddition,patientswithfrontallobe
lesionsshowdisruptedimitationinhibitionbehaviour(Brassetal.,2003;Spengleretal.,
2010)andanincreasedtendencytoautomaticallyimitateevenwhentheyareclearly
instructedtonotdoso(Lhermitteetal.,1986).Moreevidencefortheinvolvementof
rTPJcomesfromneuro-stimulationstudies:inhibitingtheactivityintherTPJby
transcranialmagneticstimulation(TMS)interferedwithimitativeresponsesimpairing
imitationinhibition(Hogeveenetal.,2014;Sowden&Catmur,2015).Irrespectiveofthe
methodused,itisworthnotingthat,todate,therehaveonlybeenasmallnumberof
studiesimplicatingmPFCandrTPJinthecontrolofimitation.Moreover,thesestudies
haveusedrelativelysmallsamplesizesbetween10and25participantsandtherehave
beenfew,ifany,directreplications.Therefore,thesumtotalofevidenceformPFCand
rTPJengagementduringimitationcontrolissuggestiveratherthancompelling.
Alongwithimitativecontrol,neuroimagingfindingssuggestmPFCandrTPJare
alsoengagedinavarietyofsocio-cognitivetasksthatareassociatedwiththeoryof
mind,includingdistinguishingbetweenselffromother,perspectivetaking,aswellas
attributingbeliefs,desiresandattitudestoothers(ToM;Gallagheretal.,2000;Amodio
&Frith,2006;Ruby&Decety,2001;Aichhornetal.,2006;Decetyetal.,2002;
Santiestebanetal.,2012;Brassetal.,2009;Spengleretal.,2010).Basedonthese
findings,self-othercontrolprocesseshavethusbeenproposedasacandidate
8
mechanismforarangeofsocio-cognitivefunctions.Forexample,itisimportantto
inhibitone’sownperspectiveormentalstateandenhancethatoftheotherwhen
empathisingwithothers,takingtheirperspective,orengagingasuccessfultheory-of-
mind(deGuzmanetal.,2016;Sowden&Shah,2014).Further,atypicalself-other
controlhasbeenlinkedtodisorderscharacterisedbysocialdysfunctionincluding
autismandschizophrenia(CookandBird ,2012;Ferrietal.,2012).Overall,this
evidencesuggeststhatinimitationcontrol,itiscrucialtoinhibittherepresentationof
theother’saction,andenforceyourown,andthismechanismisguidedbyadomain-
specificneuralcircuituniquetosocialcognition(Brassetal.,2009).
Incontrasttothis“specialist”viewofimitationcontrol,however,“generalist”
theoriesofimitationsuggestthattheinhibitionofautomaticimitationdoesnotdiffer
fromanyotherpre-potenttendenciesorgeneralcognitivefunctions(Heyes,2011;
Cooperetal.,2013).MultiplecognitivecontroltasksliketheFlanker,Stroop,andSimon
tasks,whichrequiretheinhibitionofautomaticoverlearnedresponsetendencies,have
beenfoundtoengageadomain-generalcontrolnetworkidentifiedinthedorsolateral
fronto-parietalcortices(Aronetal.,2014;Bungeetal.,2002;Hazeltineetal.,2007;Nee
etal.,2007;Wageretal.,2005).Thisnetworkisalsocalledthemultipledemand(MD)
networkasitisengagedacrossadiversityofmentaloperations(Duncanetal.,2010).
Acrossstudiesthatinvestigateimitationinhibition,somehavefoundengagementofthe
mPFCandrTPJ(Brassetal.,2001;2005;2009;Spengleretal.,2009),whereasothers
showengagementoftheMDnetwork(Bien,Roebroeck,Goebel,&Sack,2009;
Crescentini,Mengotti,Grecucci,&Rumiati,2011;Cross&Iacoboni,2013;Mengotti,
Corradi-Dell’Acqua,&Rumiati,2012;Marshetal.,2016).However,mostpreviousfMRI
studieshavebeenlimitedbylowstatisticalpowerandsmallsamplesizes.More
9
recently,amulti-experimentstudyusinglargersamplesizes(N=28,N=50)anda
functionalregionofinterest(fROI)approachthatbolstersstatisticalpowerand
functionalsensitivityhasshownthatimitationcontrolengagesonlytheMDnetwork,
andnotmPFCorrTPJ(Darda,Butler&Ramsey,2018).Indeed,evenwithanapriori
poweranalysisensuring80%powertodetectmediumeffectsizes,Dardaand
colleagues(2018)didnotevenfindadirectionaltrendtosuggestthattheToMnetwork
wasdirectlyengagedduringimitationcontrol.
Asmentionedbefore,imitationcontrolcanbedividedintoatleasttwo
componentprocesses–actionrepresentationandactionselection.Theabovereviewof
literaturesuggeststwopossibleneuralmechanismsasbeingkeytoactionselection
duringimitationcontrol.Ononehand,duringimitationcontrol,theneural
representationgeneratedbytheobservedperson’sactionisinhibited,andtheself-
generatedactionisselectedandenforcedandthisselectionmechanismengagesa
domain-specificneuralnetworki.e.themPFCandrTPJ.Ontheotherhand,theselection
mechanismmaybeguidedbyadomain-generalneuralnetworki.e.theMDnetwork.In
bothpossiblemechanisms,theinputisthesamei.e.theobservedpersonandaction
mayengagedomain-specificsocio-perceptualneuralcircuits.However,thedifference
liesintheselectionorcontrolmechanismthatunderliestheinhibitionofautomatic
imitativetendencieswhichfinallyleadstoconsequentbehaviour(seegraphical
representationinFigure1).
Thequestionofinterestforthecurrentmeta-analysis,therefore,liesatthe
selectionstageofimitationcontrolwiththeevidencetodateforengagementofdomain-
specificanddomain-generalneuralnetworksbeinginconsistent.Eventhoughthemost
statisticallypowerfulfMRIstudytodateonlyshowstheengagementoftheMDnetwork
10
(Dardaetal.,2018),theinterpretationofindividualstudiesremainslimitedinscopefor
severalreasons.First,manysinglestudiesarelikelytobeunderpoweredleadingto
missedorspuriousresults(Buttonetal.,2013).Second,empiricalworkinvolvesdesign
choicesthatstronglyinfluenceresults,makingithardertogeneraliseeffectsacross
analysispipelinesanddifferingexperimentalprocedures(Carp,2012).Giventhe
inconsistencyofpriorfindingsandtheabsenceofaquantitativesynthesisofevidence,
takingameta-analyticalapproachtofurtherinvestigatetheneuralbasisofimitation
hasmanybenefits(Cumming,2014).Assuch,bymeansofameta-analysis,thecurrent
paperenablesthedetectionofconsistentpatternsofactivationacrossstudies.
Inordertoquantifytheconsistencyandspecificityofregionalactivationfor
imitationcontrolacrossstudies,weperformedamulti-levelkerneldensityanalysis
(MKDA;seeMethodsandMaterialsfordetails).WeincludedallfMRIstudies(N=12)
investigatingimitationcontrolusingtheRTmeasureofimitationinhibition(seeTable
1).Ourprimarymeasureaimedtoquantifytheconsistencyofregionengagement
acrossstudieswithparticularfocusontheengagementoftheToMnetworkandtheMD
network.Thedependentvariablewasthebloodoxygenleveldependent(BOLD)
responsemeasuredintheincludedfMRIstudies.Giventhepriormixedfindingsacross
studies,thismeta-analysisaimedtoquantifytheextenttowhichToM,MDorboth
neuralnetworksmaybeengagedwhenduringtheinhibitionofautomaticimitation.
Wealsorantwomoreexploratoryanalyses,whichwerebasedonasmallsubset
ofthetotalstudies.Themostcommonmeasureofimitationinhibition,thegeneral
compatibilityeffect,alsoincludesaspatialcomponent(Heyes,2011).Inorderto
measureimitativecompatibilitymorespecifically,therefore,imitativeandspatial
effectsneedtobedissociated(Gowenetal.,2016;Boyeretal.,2012;Catmur&Heyes,
11
2011).However,onlyafewfMRIstudieshavemeasuredtheimitativecompatibility
effectindependentofthespatialcomponent(Dardaetal.,2018;Marshetal.,2016;
Crossetal.,2013).ThismakesitdifficulttointerprettherolesoftheToM(mPFCand
rTPJ)andMDnetworksinimitationcontrol–theirengagementcouldreflectbothsocial
(imitative)and/ornon-social(spatial)control.Indeed,therTPJhasbeenpreviously
associatedwithorientingtobothsocialandnon-socialstimuli(Corbettaetal.,2008;
Thieletal.,2004).Thus,giventhatonlyafewstudieshavedissociatedbetween
imitative(N=3)andspatialcompatibility(N=4)effects,wealsorantwofurther
exploratoryMKDAsinordertoquantifyconsistencyofpatternsacrossstudiesforboth
imitativeandspatialcompatibilityeffects.Indeed,giventhelownumberofstudies
includedinthesecondaryanalyses,theseresultsprovideonlysuggestive,andnot
compelling,evidenceregardingtheroleoftheMDandToMnetworksinimitativeand
spatialcontrol.
MethodsandMaterials
Literaturesearchanddatacollection
Inthecurrentpaper,wefollowrecentguidelinesputforwardformeta-
analysingneuroimagingstudies(Mulleretal.,2018).FMRIstudiesexploringthe
inhibitionofautomaticimitativetendenciesweresearchedforontheonlinedatabase
PubMed,aswellasthearticlesearchengineGoogleScholar.Combinationsofkeywords
including‘imitationinhibition,’‘fMRI,’‘imitation,’‘automaticimitation,’and‘imitation
control’wereusedtoidentifyrelevantliterature(priortoJanuary2019).Atotalof15
studieswerefound.Werejectedstudiesiftheprimarymethodofinvestigationwasnot
fMRI,ifthestudydidnotreportresultsinstereotacticcoordinatespace(either
MontrealneurologicalInstitute(MNI)orTalaraichcoordinates)(N=1;Bienetal.,2009),
12
ifreportedresultswerebasedonregion-of-interest(ROI)analyses,andthestudydid
notreportwhole-brainanalysiscoordinateseitherinthemainarticleorin
supplementarymaterials(orwecouldnotobtainthemfromtheauthors)(N=1;Brasset
al.,2009),andifthestudyinvolvedchildrenoratypicalpopulations(andthe
coordinatesforcontrolswerenotreportedseparately)(N=1;Spengler,Bird,&Brass,
2010).
Awidevarietyofcontrastsareusedinstudiesthatinvestigatetheinhibitionof
automaticimitation.However,inordertominimiseheterogeneity,studiesthatuseda
paradigmthatwasnotbasedonorwasnotconceptuallysimilartotheBrassetal.
(2000)paradigmformeasuringinhibitionofautomaticimitationwerealsoexcluded.
Thus,12studieswithatotalof300participantswereincludedinthemeta-analysis(see
Table1).
Eventhoughourmainanalysiswasonthegeneralcompatibilityeffect,wealso
rantwoseparatemeta-analysesforspatialandimitativecompatibility.Table2
summarisesthecontrastsusedinthecurrentmeta-analysisforgeneral,spatial,and
imitativecompatibilityeffects.Atotalof13contrastsacross12studieswith142foci
wereusedforgeneralcompatibility,4contrastsacross4studieswith42fociwereused
forspatialcompatibility,andatotalof3contrastsacross3studieswith20fociwere
usedforimitativecompatibility.
Dataanalysis
AllanalysesinthecurrentpaperwereperformedinMatlabR2015b
(Mathworks,Naticks,MA)usingtheMKDAtoolboxdevelopedbyWageretal.,2007;
http://wagerlab.colorado.edu).MKDAisananalysistechniquethatusesarandom
effectsmodeltoassessconvergenceacrossstudies.Thisallowsforassessing
convergenceacrossstudiesasopposedtobetweenindividualfoci(asimplementedin
13
classicalmeta-analysistechniquesthatusefixedeffectsanalyses).Thus,resultsarenot
biasedbyasmallnumberofindividualstudies.Further,eachcontrastisweightedby
thesamplesizeandstudyquality(i.e.whetherthestudyusedfixedorrandomeffects
model;Wageretal.,2007;KoberandWager,2010).
MKDAwasperformedonallthreecompatibilitytypesseparately.Before
performingtheanalyses,weextractedthefollowinginformationfromeachstudyand
includeditinourdatabase:authors,yearofpublication,samplesize,taskcontrasts,
fixedorrandomeffectsmodel,andMNIorTalaraichco-ordinates.Co-ordinates
reportedinTalairachspacewereconvertedtoMNIstereotacticspaceusingLancaster
transformation(tal2icbmtransform;Lancasteretal.,2007).Peakcoordinatesfromeach
contrastmapwerethenconvolvedwitha10mmsphericalkernelinordertocreatea
contrastindicatormap(CIM).Theresultingvoxelswithin10mmofthepeakwere
deemed“significant”andgivenavalueofone;othervoxelsweregivenavalueofzero
whichindicatednosignificanteffect.Adensitymapwasthencreatedbyaveragingthe
indicatormaps,weightedbysamplesize,andwhetherthestudyusedafixedorrandom
effectsmodel.Morespecifically,asrecommendedbyWagerandcolleagues(Wager,
Lindquist,&Kaplan,2007),thisdensitymapwasweightedbythesquarerootofthe
samplesizeofthestudy,andthenmultipliedbyanadjustmentfactorof1forrandom
effectsanalysis,and.75forafixedeffectsanalysis.
EachvoxelofthedensitymapwasgivenadensitystatisticP.Pstandsforthe
proportionofcontrastsincludedintheanalysisthatshowactivitywithin10mmofthe
voxel.AMonteCarlosimulation(with5000iterations)wasthencarriedoutinorderto
identifyvoxelsthathadaP-statisticthatwashigherthanthefrequencypredictedby
chance.Thiswastestedagainstthenullhypothesisthatactivatedregionsinthe
resultingpairwisecontrastmaps(fromthe5000iterations)wererandomlydistributed
14
acrossthebrain.Totestforthesignificanceoftheclustersize,asimilarprocedurewas
used.Thisallowedfortheidentificationofathresholdforclustersizeatwhichaspecific
numberofvoxelsneededtobeactivatedcontiguouslysothattheclustercouldbe
deemedsignificant.
Inordertomaximisesensitivityintestingourhypotheses,wereportresults
usingtwothresholdingtechniques.Onethresholdingtechniqueisbasedonheightand
theotherisbasedonclustersize.FortheweightedP-statistic(height-basedthreshold),
thefamilywiseerror(FWE)correctedthresholdistheproportionofstudieswhich
yieldedactivitywithin10mmofavoxelthatshowedahigherP-statisticthanthe
maximumP-statisticacross95%oftheMonteCarlomaps.Fortheclustersize
threshold,theFWEcorrectedthresholdisthecontiguousvoxelsobservedattwo
differentthresholds(p<.001andp<.01)whoseclustersizeismorethantheextentof
clustersfoundacross95%oftheMonteCarlomaps.Weusetwocluster-based
thresholdsinordertoalsodetectregionsthatshowalowerresponseinmagnitudeover
alargerclustersizebothatmorestringent(p<.001)andlessstringent(p<.01)
thresholds.Voxelsthatexceedtheheight-basedthresholdinouranalysisappearonthe
resultingmapsinFigure2inyellow,andthosethatexceedtheclusterextent-based
thresholdappearinorange(p<.001)andred(p<.01).
Intheresultingtable(Table3),peakactivationfocithatpasstheheight-based
thresholdarereported.Ifactivationsdonotpasstheheight-basedthreshold,fociofthe
cluster-extent-basedthresholdingarereported.Thenumberofvoxelsineachcluster
thatsurvivedheight-basedand/orextent-basedthresholdingisalsoreported.Resulting
coordinateswerelocalisedusingtheSPMAnatomyToolbox(Eickhoffetal.,2005).The
databaseofco-ordinates,andcodeusedtoperformthemeta-analysisareavailable
online(https://osf.io/dbuwr/).
15
Results
Forthegeneralcompatibilityeffect,across13contrastsfrom12studies,
consistentactivationwasfoundinrightinferiorparietallobule,rightsupramarginal
gyrus,rightsuperiortemporalgyrus,andrighttemporo-parietaljunction(seeTable3;
Figure2A).Theseclusterssurvivedbothheight-basedandthemorestringentextent-
basedthresholding(p<.001).Activationwasalsofoundinrightsuperiorfrontalgyrus,
andrightmiddlefrontalgyrus,whichsurvivedbothheightandthelessstringentextent-
basedthresholding(p<.01).Activationintheleftandrightinsulasurvivedthemore
stringentextent-basedthreshold(p<.001),butnottheheight-basedthreshold.
ActivationintherightIFGsurvivedthelessstringentextent-basedthreshold(p<.01)
butnottheheight-basedthreshold.
WerantwofurtherMKDAsseparatelyforspatialandimitativecompatibility.
Forspatialcompatibility,across4contrastsfrom4studies,wefoundconsistent
activationthatwithstoodtheheight-basedthresholdingintheleftIPLandtherightSFG
(seeTable3;Figure2B).Noregionswithstoodcluster-basedthresholding.Forimitative
compatibility,across3contrastsfrom3studies,wefoundconsistentactivationinthe
leftIPLthatsurvivedheight-based(seeTable3;Figure2C).Activationwasalsofoundin
therightIPL,whichwithstoodheight-basedaswellasthelessstringentextent-based
thresholding(p<.01).
Thesedensitymapsshowingregionsthatwithstoodbothheightand/orcluster-
extentthresholdingforeachcompatibilitytypewerethenoverlaidwiththeToMand
MDnetworkmasksseparately.TheToMnetworkmaskconsistedoffourparcels
includingthedorsal,medial,andventralmedialprefrontalcortex(DMPFC,MMPFC,
VMPFC),andtherighttemporo-parietaljunction(rTPJ),whichhavepreviouslybeen
implicatedinmentalisingortheory-of-mind(Dufouretal.,2013).FortheMDnetwork
16
mask,16parcelswereusedwhichincludedareasinbilateralsuperiorandinferior
parietallobules(SPL,IPL),intraparietalsulcus(IPS),inferiorandmiddlefrontalgyrus
(IFG,MFG),precentralgyrus(PrecG),insula(Ins),andthesupplementarymotorarea
(SMA)(availableat:https://evlab.mit.edu/funcloc/download-parcels).Overlayofthe
densitymapswiththeToMandMDnetworkmasksallowedforidentificationofoverlap
betweenregionsthatwereconsistentlyactivatedintheMKDAandtheToMandMD
networks(Figure3).Forallcompatibilitytypes(general,imitativeandspatial),all
regionsthatpassedheightorextent-basedthresholdingoverlappedwithregionsinthe
MDnetwork(Figure3A).Additionally,onecluster,whichshowedconsistentactivation
forgeneralcompatibility,alsooverlappedwiththerightTPJintheToMnetwork(Figure
3B).TherewasnooverlapwiththemPFCnodeoftheToMnetworkforany
compatibilitytype.
InordertobreakdowntheroleoftherightTPJingeneralcompatibility,we
performedafurther,moreexploratoryanalysis.Wecomparedpeakcoordinatesfrom
priorstudieswitharightTPJmask,whichhasbeenpreviouslyimplicatedintheory-of-
mind(Dufouretal.,2013).Todoso,theToMnetworkmaskforrTPJwasoverlaidwith
thecontrastindicatormapsofallstudiesusedforimitative(N=3)andspatial(N=4)
compatibility.Thecontrastindicatormapsinclude10mmsphericalkernelsaround
peakcoordinatesofeachcontrast.Thisallowscoordinatesfrompriorimitativeand
spatialcompatibilitycontraststobedisplayedwithoutanythresholdingrestrictions
andoverlaidwiththerTPJnodeoftheToMnetwork.Figure4showsoverlapbetween
contrastindicatormapsforgeneralcompatibilityandspatialcompatibilitywiththe
rightTPJnodeoftheToMnetworkmask.Bycontrast,thereisnooverlapbetween
contrastindicatormapsforimitativecompatibilityandthesamerightTPJmask.
17
Discussion
Inthecurrentpaper,weperformedameta-analysisoffMRIstudiesinordertoquantify
theconsistencyandspecificityofregionalactivationduringtheinhibitionofautomatic
imitation.Ourresultssupporteda“generalist”viewofimitationcontrol–wefound
clearengagementofdorsolateralfrontoparietalcorticeswhenobservinganactionthat
conflictedwithacurrentmotorintention.Theseregionsoverlappedwithregions
associatedwiththeMDnetwork.Wefoundlessevidencefora“specialist”viewof
imitationcontrol,whichreliesontheToMnetwork.Indeed,therewasnoengagementof
mPFCacrossstudiesandtherewasnoclearevidenceregardingtheengagementofrTPJ;
therewasonlysuggestiveevidencethatitmayreflectspatialratherthansocialcontrol.
Thus,ourresultsprovideunambiguoussupportfortheengagementofadomain-
generalneuralnetworkduringthecontrolofimitation,andonlylimitedevidencefor
theengagementofadomain-specificneuralnetworkthatistiedtosocialcognition.
Studiesinvestigatingtheneuralcorrelatesofimitationcontrolhavetodate
shownmixedevidencefortheengagementofdomain-generalanddomain-specific
neuralnetworksinimitationinhibition.Whilesomestudieshavefoundengagementof
themPFCandrTPJ(Brassetal.,2001;2005;2009;Spengleretal.,2009),othersshow
engagementoftheMDnetwork(Bien,Roebroeck,Goebel,&Sack,2009;Marshetal.,
2016;Dardaetal.,2018).ThecurrentMKDAdemonstratedthatbrainregionsinthe
multipledemandnetworkarereliablyandconsistentlyengagedacrossstudiesthat
investigateimitationinhibitionusingthegeneralcompatibilityeffect.Brainregionsin
theMDnetworkarealsoengagedforimitative(bilateralIPL)andspatialcompatibility
effects(leftIPL,rightSFG).Thus,ourfindingssuggestthatbrainregionsthatare
engagedacrossarangeofcognitivecontroltasksarealsoreliablyengagedwhen
18
controllingtheautomatictendencytoimitateothers,asmeasuredbygeneraland
imitativecompatibilityeffects.
Evidencesupportingtheengagementofadomain-specificneuralcircuitthatis
centraltosocialcognitionandincludesmPFCandrTPJwaslessconsistentinthe
currentmeta-analysis.Brassetal.(2009)proposedthattherTPJwasinvolvedin
distinguishingbetweenself-andother-generatedactions,whereasthemPFCwas
engagedwhenenforcingthecorrectaction.However,thecurrentMKDAdidnotfind
anyevidenceofanteriormPFCengagementforeithergeneral,spatial,orimitative
compatibilityeffects.AnabsenceofmPFCengagementforimitationcontrolacross
studiesisthusinconsistentwiththehypothesisthataspecificneuralsystemrelatedto
socialcognitionisalsoengagedduringtheinhibitionofautomaticimitation(Brassetal.,
2009).
IncontrasttotheresultsreportedinmPFC,acrossstudiesinvestigating
imitationinhibitionasmeasuredbythegeneralcompatibilityeffect,thecurrentmeta-
analysisfoundengagementofrTPJ.However,itisdifficulttointerprettheroleofrTPJin
imitationcontrolforatleasttworeasons.First,thegeneralcompatibilityeffectisa
productofbothspatialandimitativeeffects,whichmakesithardtointerpretina
straightforwardmanner.Second,rTPJisinvolvedinbothsocialandnon-social
processes,whichmakesitafunctionallyheterogenousregion(Corbettaetal.,2008;
Kralletal.,2015,2016;Lee&McCarthy,2016;Schuwerketal.,2017).
Further,inthecurrentmeta-analysis,across12studies,wefindengagementof
rTPJforthegeneralcompatibilityeffect.However,itisimportanttodistinguish
betweenasynthesisofevidencebasedonadescriptiveapproach,andaquantitative
meta-analysis(Gigerenzer,2018).Todate,14fMRIstudieshaveinvestigatedimitation
controlbymeasuringthegeneralcompatibilityeffect(weexcludedBienetal.,2009and
19
Brassetal.,2009inthemeta-analysis,seeMethods).Outofthe14studies,only4
studiesreporttheengagementofrTPJforthegeneralcompatibilityeffect(seeDardaet
al.,2018,Table1formoredetails).Thus,wefindthatonly28.6%offMRIstudieson
imitationcontroltodate(4/14)showanyevidenceinsupportofaroleofrTPJin
imitationcontrol,andthesestudiesdonotdissociatebetweenspatialandimitative
effects.
InthelargestandmostsensitivefMRIstudyofimitationinhibitiontodate,
Dardaandcolleagues(2018)showednoengagementofrTPJfortheimitative
compatibilityeffect,butengagementofrTPJforgeneralandspatialcompatibility
effects.Similarly,inthecurrentmeta-analysis,whenweexploredtheunthresholded
spatialandimitativecompatibilityeffectmapsseparately,therewaspartialoverlap
betweenthespatialcompatibilityeffectandrTPJ,butnooverlapbetweentheimitative
compatibilityeffectandrTPJ.GiventhatthesmallnumberoffMRIstudiesinvestigating
spatialandimitativecompatibilityeffectsseparately(N=4andN=3,respectively),the
currentfindingsneedtobeinterpretedwithcaution.However,whentakentogether
withpriorfindings,theresultsprovideconsistentlylimitedevidencefortheunivariate
engagementofrTPJinthecontrolofimitativetendencies.Incontrast,currentfMRI
findingsprovidemoreevidencethatrTPJisinvolvedinresolvingspatialconflict,which
isinkeepingwithpatientwork(Vallar&Perani,1987;Valleretal.,1993),aswellas
evidenceusingspatialcueingtaskslikethePosnerparadigm(Posner&Cohen,1984;
Thieletal.,2004;Corbettaetal.,2008).MorerecentworkalsosuggeststhatrTPJmay
playamoredomain-generalroleintheprocessofcontextualupdating,actingon
changingexpectationsafterunexpectedevents(Geng&Vossel,2013;Mengottietal.,
2017).Assumingthatonincompatibletrialsexpectationsareviolated,rTPJmayplaya
moregeneralisedroleofcontextupdatinginimitationandspatialcontrol.However,
20
irrespectiveofwhetheritplaysadomain-specificordomain-generalrole,inthecurrent
meta-analysis,wefindlimitedevidencefortheunivariateengagementofrTPJinthe
controlofautomaticimitativetendencies.
Limitationsandalternativeinterpretations
Beforemovingontothewidertheoreticalimplicationsoftheseresults,wefirst
acknowledgepossiblelimitationstothecurrentmeta-analyticalapproach.Thecurrent
meta-analysisdidnotincludeworkbyBrassandcolleagues(2009),whichimplicated
rTPJandmPFCinimitationcontrol,duetothewhole-braindatabeingunavailable.
Nonetheless,asmentionedbefore,only28.6%(4/14)offMRIstudies,whichhave
investigatedimitationcontrol,foundengagementofmPFCandrTPJ,andtheyallhad
smallsamplesizes(between10and20participants).Itis,therefore,unlikelythatthe
inclusionofanadditionalstudywitharelativelysmallsamplesize(Brassetal.,2009)
wouldchangetheresultsofthemeta-analysis,giventhattheyareweightedbysample
size.
AfurtherconsiderationistherelativesizeoftheMDandToMnetworksthatwe
usedinouranalyses.GiventhattheMDnetworkspansamuchlargerareathantheToM
network,ouranalysismaybebiasedtowardfindingresultsintheMDnetworkoverthe
ToMnetwork.Althoughthisistrueinarelativesense,wedonotfeelthatithindersour
interpretationoftheresultsintheToMnetworkforseveralreasons.First,regionsof
interestintheToMnetworkwerenotparticularlysmallareas.ThemPFCregions
includedseveralportionsofthedorsal,middle,andventralmPFC,andtherTPJcovered
arelativelylargeareaofcortex.Second,bothnetworksweredefinedaccuratelybased
onpriorwork,whichusedlargesamplesofparticipants.Thus,eventhoughToMareas
werecomparativelysmallerthantheMDnetwork,theystillcoveredaswathofcortexin
21
regionsfunctionallyandpreciselydefinedastheToMnetwork.Consequently,wefeel
confidentthathadtheseregionsbeenconsistentlyengagedacrossstudies,wewould
havebeenabletodetectthem.Third,evenifweonlyuseCIMsacrossthewholebrain,
whichreportactivationpeaksfrompriorstudies,thusavoidingissueswith
thresholdingorchoiceofmasks,westilldonotfindevidenceforengagementnearrTPJ
andmPFCfortheimitativecompatibilityeffect(Figure4).
Anadditionalpossibilitytoconsideristhatthedifferencebetweentheresults
intermsofdomain-specificanddomain-generalnetworkengagementcouldbedueto
thedifferencesinstimuliusedinthestudiesincludedinthemeta-analysis.However,
thetasksareallconceptually,visuallyandcognitivelysimilartoeachotherwithonly
minordifferencesacrossallstudies.Forexample,inDardaetal.,(2018;Exp1and
Exp2),thestimuliconsistofindexandmiddlefingermovements,whereasinWangetal.
(2011),handopeningandclosingmovementsareused.Moreover,arecentmeta-
analysisalsoshowedthatbehaviouralperformanceisconsistentacrossarangeof
studiesthatcoverarangeofminormethodologicaldifferences(Craccoetal.,2018).
Giventhelackofsubstantialdifferencesbetweenthestudiesandtheconsistentpattern
ofbehaviouraldata,itseemsunlikelythatsmalldifferencescouldberesponsiblefor
theseeffects.
Finally,weacknowledgethatfMRIisonlyoneformofmeasurement,anditis
importanttoconsiderhowthesefindingsmeshwithresultsfromotherneuroscience
techniques.Forinstance,neurostimulationstudieshaveimplicatedrTPJinimitation
control(Santiestebanetal.,2015;Bardietal.,2017).Usingrepetitivetranscranial
magneticstimulation(TMS),dampeningofactivityintherTPJinterferedwithimitative,
butnotspatialresponses(Hogeveenetal.,2014;Sowden&Catmur,2015),whereas
excitatorystimulationoftherTPJbyanodaltranscranialdirectcurrentstimulation
22
(tDCS)causedincreasedperformanceontheimitationtask(Santiestebanetal.,2012).
Further,inpatientswithlesionsinthetemporoparietaljunctionarea,imitation
inhibitiondeficitshavebeenfoundtocorrelatewithdeficitsinvisualandcognitive
perspectivetakingtasks,furthersupportingtheroleofrTPJinimitationcontrol
(Spengleretal.,2010).Thus,thereseemstobeadiscrepancybetweenneurostimulation
andpatientstudies,andresultsfromthecurrentmeta-analysisoffMRIstudies.The
evidencefromneurostimulationandpatientstudiesfortheengagementofrTPJin
imitationcontrolis,however,limitedtoafewstudieswithsmallsamplesizes.Under
anyyardstick,therefore,thesumtotalofevidencefromneurostimulationandpatient
studiescanonlybejudgedtobesuggestiveatpresent.Itisbasedonafewstudieswith
smallsamplesizesthatlackformalpoweranalysesandreplications.Therefore,for
moreconfirmatoryevidence,futureinvestigationswithpre-registeredandadequately
poweredreplicationsareessential(Munafoetal.,2017;Zwaanetal.,2018;Nelsonetal.,
2018).Inaddition,itisalsopossiblethattheroleofrTPJinimitationcontrolcannotbe
capturedbyunivariatemeasurementsandamorecomplexneuralorganisationisat
playduringimitationcontrol.
Theoreticalimplications
ThelackofconsistentactivationinmPFCinthecurrentmeta-analysisanda
difficultyininterpretingtheroleofrTPJhaveimplicationsfor“specialist”theoriesof
imitation.“Specialist”theoriessuggestthatbasedonadedicatedneuralcircuitforsocial
cognition,self-othercontroliscrucialfortheregulationofimitation,empathy,autism,
andtheory-of-mind(Brassetal.,2009;deGuzmanetal.,2016;Sowden&Shah,2014).
However,morerecentbehaviouralevidencesuggeststhatimitationmaynotvaryasa
functionofautistic-liketraitsorempathy,thusquestioningtherelianceofimitation
23
inhibitiononadistinctlysocialmechanism(Butleretal.,2015;Craccoetal.,2018;
Genschowetal.,2017).Insteadofadistinctlysocialmechanism,imitationcontrolmay
involvedomain-generalcognitivecontrolmechanisms,whicharealsoengagedduring
thecontrolofothernon-socialpre-potentresponsetendencies(Heyes,2011;Cooperet
al.,2012).Indeed,thedual-routemodelofautomaticimitationproposedbyHeyes
(2011)canexplainthecontrolofautomaticimitativetendencieswithoutassuminga
relianceonaself-otherdistinction.Themodelsuggeststhatlikeotherstimulus-
responsecompatibilitytasks,imitationcontrolismediatedbylong-termstimulus-
responseassociationswhichareaproductoflearning.Inlinewiththis,the
computationalmodelputforthbyCooperetal.(2012)furthersubstantiatesthisnotion
bydemonstratingthatspatialandimitativecompatibilityeffectsdependonsimilar
cognitiveprocesses,andanybehaviouraldifferencesareaccountedforbydifferentsets
ofinputnodesforspatialandimitativeeffectsinageneraldual-routeframework(but
seeBerthental&Scheutz(2013)foracritiqueofthismodel).
Eventhoughitispossiblethatimitationandspatialcompatibilityrelyona
partlysharedsetofcognitiveprocesses,thisdoesnotaddressthequestionofwhether
theseprocessesalsorelyonsimilarordistinctneurobiologicalmechanisms.The
currentmeta-analysissuggeststhattheselectionmechanisminimitationinhibitionis
guidedbyadomain-generalmultipledemandsystem,whichisalsoengagedduringthe
inhibitionofothernon-socialexternalinfluences.However,alackofengagementof
mPFC(andpossiblyrTPJ)inimitationcontroldoesnotimplythattheydonotalsoplay
aregulatoryroleinimitationcontrol.Forexample,mPFChasbeendemonstratedto
exertatop-downinfluenceduringmodulationofimitationviadirectgaze(Wangetal.,
2011).Inaddition,rTPJshowedahigherresponsewhenaninteractionpartnerwas
believedtobehumanandlookedhumancomparedtowhentheseanimacycueswere
24
absent(Klapperetal.,2014).ThesefindingssuggestthatmPFCandrTPJmayplaya
regulatoryroleinimitationcontrolandmaybefunctionallyconnectedtoother
networkswithoutbeingdirectlyengaged(Burnett&Blakemore,2009).Thecurrent
findingssuggestthatfutureworkshouldpostulateandtestmorecomplexmodelsof
imitationcontrol,whichextendbeyondtheoperationsofthetheoryofmindnetwork.
Inasimilarmanner,othersocio-perceptualcircuits,whichextendbeyondthe
MDnetwork,mayalsobeinvolvedwheninhibitingautomaticimitativetendencies.In
thisregard,itisimportanttonotethedistinctionbetweeninput-andmechanism-
specificity.Ofcourse,theinputintheimitationinhibitiontaskcanbereadilyidentified
asemanatingfromasocialentityi.e.ahumanhand.Thus,theobservedinputisclearly
socialinthesensethattheobservedagentoffersopportunityforsocialinteraction.
Althoughtheperceptualinputissocial,adomain-generalselectionmechanismmaystill
operateinimitationcontrol.Indeed,itispossiblethatthesameselectionmechanism
operatesacrossbothsocialandnon-socialcontexts.Inthecontextofimitation,
therefore,domain-specificactionobservationandpersonperceptionnetworksmay
functionallyinteractwithdomain-generalcontrolmechanismsintheMDnetwork(see
Figure1).Thus,similartootherdomainsofsocialinformationprocessing,aninterplay
betweendomain-generalanddomain-specificnetworksmayresultinthecontrolof
automaticimitativetendencies(Baldauf&Desimone,2014;Spunt&Adolphs,2017;
Zakietal.,2010).Thus,theengagementofdomainspecificanddomaingeneralneural
networksinimitationcontrolmaybemorecomplicatedthatwhatcurrentmodelsof
imitationsuggest.Consequently,theoriesthatmovebeyondaneatdivisionandposit
linksbetweendomain-generalanddomain-specificsystemsinimitationcontrolneedto
begivengreateremphasisinfuturework(Barrett,2012;Spunt&Adolphs,2017;
Michael&D’Ausilio,2015;Binney&Ramsey,2019).
25
Inconclusion,thecurrentmeta-analysisprovidesevidencethattheselection
mechanismwheninhibitingautomaticimitativetendenciesisguidedbytheregionsof
thedomain-generalmultipledemandnetworkratherthanadomain-specificsystem
relatedtosocialcognition.Ourmeta-analysisquestionstheroleofmPFCandrightTPJ
inimitationcontrol,andsuggeststhatcurrentneurocognitivemodelsofimitation
controlneedfurtherrevisioninordertoaccountforthemorecomplexnatureof
functionalinterplaybetweendomain-generalanddomain-specificsystems.
26
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Table1.Dataextractedfromthestudiesincludedinthemeta-analysis.
Authors Year Sample Contrasts Fixed/RandomEffectsModel
MNIorTalaraichcoordinates
GC SC IC
Brassetal. 2001 10 x Fixed Talaraich
Brassetal. 2005 20 x Fixed Talaraich
Spengleret
al.2009 20 x Random Talaraich
Crescentini
etal.2011 19 x Random MNI
Wangetal. 2011 20 x Random MNI
Mengotti
etal.2012 22 x x Random MNI
Cross&
Iacoboni2013 24 x x Random MNI
Crossetal. 2013 20 x x
Klapperet
al.2014 19 x Random MNI
Marshet
al.2016 24 x x x Random MNI
Dardaet
al.(Exp1)2018 28 x Random MNI
Dardaet
al.(Exp2)2018 50 x x x Random MNI
Campbell
etal.
2018 x Random MNI
TOTAL=
11 300
NB:GC=GeneralCompatibility,SC=SpatialCompatibility,IC=ImitativeCompatibility
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Table2.Contrastsusedinthemeta-analysisforgeneral,spatial,andimitative
compatibility.
Authors Year GeneralCompatibility SpatialCompatibility ImitativeCompatibility
Brassetal. 2001 GeneralIncompatible>
GeneralCompatible
Brassetal. 2005 GeneralIncompatible>
GeneralCompatible
Spengleretal. 2009 GeneralIncompatible>
GeneralCompatible
Crescentiniet
al.2011 GeneralIncompatible>
GeneralCompatible
Wangetal. 2011 GeneralIncompatible>
GeneralCompatible*
Mengottiet
al.2012 Non-specular>
Specular^
SpatiallyIncompatible>
SpatiallyCompatible
Cross&
Iacoboni2013 GeneralIncompatible>
GeneralCompatible
SpatiallyIncompatible>
SpatiallyCompatible
Crossetal. 2013 GeneralIncompatible>
GeneralCompatible
GeneralCompatibility>
SpatialCompatibility
Klapperetal. 2014 GeneralIncompatible>
GeneralCompatible*
Marshetal. 2016 GeneralIncompatible>
GeneralCompatible
SpatialIncompatible>
SpatiallyCompatible
ImitativelyIncompatible
>ImitativelyCompatible
Dardaetal.
(Exp1)2018 GeneralIncompatible>
GeneralCompatible
Dardaetal.
(Exp2)2018 GeneralIncompatible>
GeneralCompatible
SpatialIncompatible>
SpatialCompatible
ImitativeIncompatible>
ImitativelyCompatible
Campbellet
al.
2018 GeneralIncompatible>
GeneralCompatible
No.ofstudies 12 4 3
No.ofcontrasts 13 4 3
No.offoci 142 42 20
Table2showsthecontrastsusedinthecurrentmeta-analysis,andthenumberof
contrasts,foci,andstudiesforeachcompatibilitytype(general,spatial,andimitative).
*Collapsedacrossconditions;forWangetal.,2011:collapsedacrossdirectandaverted
gaze,forKlapperetal.,2014:collapsedacrossbelief(motion-capture,computer
animation)andform(human,non-human).
^Non-specular>Speculari.e.{(spatiallyincompatibleandimitativelycompatible)+
(imitativelyincompatibleandspatiallycompatible)>generalcompatible)}]
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Table3.Areasconsistentlyactivatedforgeneralcompatibility,spatialcompatibility,and
imitativecompatibility.
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GENERALCOMPATIBILITYRegion MNI MaximumP No.ofVoxels Threshold
x y zRightTPJ 60 -46 22 0.42 1 ^**
RightTPJ 56 -46 32 0.41 1 ^**
Rightsupramarginalgyrus
56 -36 36 0.44 9 ^**
RightIPL 60 -34 34 0.43 2 ^**
RightIPL 52 -30 38 0.37 5 ^**
RightMFG 34 0 54 0.45 15 ^*
RightSFG 26 -2 64 0.37 46 ^*
LeftInsulaLobe -36 14 0 0.32 453 **
-34 12 -2 213
-36 18 2 240
RightInsulaLobe 38 16 4 0.36 405 **
34 18 0 172
46 12 2 75
38 16 6 158
RightIFG 46 14 10 0.28 1269 *
44 16 -4 74
28 24 -4 44
32 12 0 41
46 22 2 113
56 10 2 116
28 20 6 105
36 26 6 66
56 16 6 128
52 12 14 219
48 2 22 92
40 8 22 132
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Table3showsareasconsistentlyactivatedforgeneralcompatibility,spatial
compatibility,andimitativecompatibility.MaximumPstandsforthemaximum
proportionofstudiesexhibitingtheeffectatthepeakdensityweightedbysamplesize.
MNI=MontrealNeurologicalInstitute(MNI)standardstereotaxicspacecoordinates.
Thevoxelsizeis2×2×2mm
3
.
*Clusterswithstandingp<.01clusterextent-basedthreshold.
**Clusterswithstandingp<.001clusterextent-basedthreshold.
^Clusterswithstandingtheheight-basedthreshold.
50 8 28 139
SPATIALCOMPATIBILITY
LeftIPL -36 -40 48 0.78 8 ^
Rightsuperiorfrontalgyrus
24 -4 58 0.78 190 ^
24 -6 54 56 ^
24 -4 60 134 ^
IMITATIVECOMPATIBILITY
Leftsupramarginalgyrus/IPL
-48 -28 34 0.73 11 ^
Rightsupramarginalgyrus/IPL
48 -26 44 0.73 18 *^
52 -30 42 7
46 -26 46 11
38
Figure1.Brainnetworksassociatedwiththecontrolofautomaticimitation.
Figure1.Brainnetworksassociatedwiththecontrolofautomaticimitation.
Thisgraphicalrepresentationdividesimitationcontrolintotwoconstituentprocesses–
representationofthepersonandtheiraction,andtheselection(control)oftheright
actiontobeexecuted.Inthecontextofautomaticimitation,therepresentationsystem
consistsinface,body,biologicalmotion,andactionperception.Theneuralsubstrates
forpersonandactionperceptionspanthefusiformgyrus,occipitotemporalcortex,and
posteriorsuperiortemporalsulcus,aswellasthemirrorneuronsystem(Kanwisher,
2010;Caspers,etal.,2010).Thecontrolorselectionsystemconsistsinabrainnetwork
thatiseitherdomain-general(i.e.themultipledemandnetwork)ordomain-specific(i.e.
thetheory-of-mindnetwork).N.B.Abbreviations:MNS=mirrorneuronsystem;IPL=
inferiorparietallobule,IFG=inferiorfrontalgyrus;pSTS=posteriorsuperiortemporal
sulcus;OT=occipito-temporalcortex;FG=fusiformgyrus,MD=multipledemand
network;ToM=theory-of-mindnetwork;mPFC=medialprefrontalcortex;PMC=
primarymotorcortex;dlPFC=dorsolateralprefrontalcortex;TPJ=temporo-parietal
junction.Thebidirectionalarrow“”indicateslinksbetweenthedifferentnodesof
imitationcontrol.
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Figure2.ConsistencyofbrainactivationfromtheMKDAAnalyses.
Figure2.ConsistencyofbrainactivationfromtheMKDAAnalyses.
Brainareasthatareconsistentlyengagedforgeneralcompatibility(A),spatial
compatibility(B),andimitativecompatibility(C).Voxelsthatexceedtheheight-based
threshold(p<.05,FDRcorrected)inouranalysisappearinyellow,andthosethatexceed
theclusterextent-basedthresholdappearinorange(p<.001)andred(p<.01).
Figure3.OverlayoftheMKDAmapswiththeToMandMDnetworkmasks.
Figure3.OverlayoftheMKDAmapswiththeToMandMDnetworkmasks.OverlayofthedensitymapswiththeToMandMDnetworkmasksallowedforidentificationofoverlapbetweenregionsthatwereconsistentlyactivatedintheMKDAandtheToMandMDnetworks.Forallcompatibilitytypes(general,imitativeandspatial),allregionsthatpassedheightorextent-basedthresholdingoverlappedwithregionsintheMDnetwork(A).Additionally,onecluster,whichshowedconsistentactivationforgeneralcompatibility,alsooverlappedwiththerightTPJintheToMnetwork(B).TherewasnooverlapwiththemPFCnodeoftheToMnetworkforanycompatibilitytype.
Figure4.OverlayofContrastIndicatorMapswithrTPJ.1
2
Figure4.OverlayofContrastIndicatorMapswithrTPJ.3
TheToMnetworkmaskforrTPJoverlaidwiththecontrastindicatormapsofallstudies4
usedforgeneral(N=12;A)imitative(N=3;B)andspatial(N=4;C)compatibility.There5
wasoverlapbetweencontrastindicatormapsforgeneralcompatibilityandspatial6
compatibilitywithrightTPJ.Thereisnooverlapbetweencontrastindicatormapsfor7
imitativecompatibilityandthesamerightTPJmask.8
Abbreviations:IC=ImitativeCompatibility;SC=SpatialCompatibility,GC=General9
Compatibility10
11
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Ethicsstatement37
Thecurrentworkwasameta-analysisofexistingdataandtherewerenoethical38
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