"Hyperscans" Show How Brains Sync as People Interact

Scientific American is the essential guide to the most awe-inspiring advances in science and technology, explaining how they change our ... SkiptomaincontentSupportScienceJournalismSubscribeShareonFacebookShareonTwitterShareonRedditShareonLinkedInShareviaEmailPrintCredit:JohnWildgooseGettyImagesAdvertisement Thevastmajorityofneuroscientificstudiescontainthreeelements:aperson,acognitivetaskandahigh-techmachinecapableofseeinginsidethebrain.Thatsimplerecipecanproducepowerfulscience.Suchstudiesnowroutinelyyieldimagesthataneuroscientistusedtoonlydreamabout.Theyallowresearcherstodelineatethecomplexneuralmachinerythatmakessenseofsightsandsounds,processeslanguageandderivesmeaningfromexperience. Butsomethinghasbeenlargelymissingfromthesestudies:otherpeople. Wehumansareinnatelysocial,yetevensocialneuroscience,afieldexplicitlycreatedtoexploretheneurobiologyofhumaninteraction,hasnotbeenassocialasyouwouldthink.Justoneexample:noonehasyetcapturedtherichcomplexityoftwopeople’sbrainactivityastheytalktogether.“Wespendourliveshavingconversationwitheachotherandforgingthesebonds,”neuroscientistThaliaWheatleyofDartmouthCollegesays.“[Yet]wehaveverylittleunderstandingofhowitispeopleactuallyconnect.Weknowalmostnothingabouthowmindscouple.” GroupBrainprints Thatisbeginningtochange.Agrowingcadreofneuroscientistsisusingsophisticatedtechnology—andsomeverycomplicatedmath—tocapturewhathappensinonebrain,twobrains,oreven12or15atatimewhentheirownersareengagedineyecontact,storytelling,jointattentionfocusedonatopicorobject,oranyotheractivitythatrequiressocialgiveandtake.Althoughthefieldofinteractivesocialneuroscienceisinitsinfancy,thehoperemainsthatidentifyingtheneuralunderpinningsofrealsocialexchangewillchangeourbasicunderstandingofcommunicationandultimatelyimproveeducationorinformtreatmentofthemanypsychiatricdisordersthatinvolvesocialimpairments. Previouslimitsontechnologywereamajorobstacletostudyingrealhumaninteraction.Brainimagingrequiresstillness,andscientificrigordemandsalevelofexperimentalcontrolthatisanythingbutnatural.Asaresult,itishardtogeneratehigh-qualitydataaboutonebrain.Doingsofortwobrainsis“morethantwiceashard,”neuroscientistDavidPoeppelofNewYorkUniversitysays.“Youhavetosynchronizethemachinery,thedataandthedataacquisition.” Nevertheless,thefirststudytosuccessfullymonitortwobrainsatthesametimetookplacenearly20yearsago.PhysicistReadMontague,nowatVirginiaTech,andhiscolleaguesputtwopeopleinseparatefunctionalmagneticresonanceimaging(fMRI)machinesandobservedtheirbrainactivityastheyengagedinasimplecompetitivegameinwhichoneplayer(thesender)transmittedasignalaboutwhetherheorshehadjustseenthecolorredorgreenandtheotherplayer(thereceiver)hadtodecideifthesenderwastellingthetruthorlying.Correctguessesresultedinrewards.Montaguecalledthetechniquehyperscanning,andhisworkproveditwaspossibletoobservetwobrainsatonce. Initially,Montague’sleadwasfollowedmostlybyotherneuroeconomistsratherthansocialneuroscientists.Butthetermhyperscanningisnowappliedtoanybrainimagingresearchthatinvolvesmorethanoneperson.Todaythetechniquesthatfitthebillincludeelectroencephalography(EEG),magnetoencephalographyandfunctionalnear-infraredspectroscopy.Useofthesevariedtechniques,manyofthemquitenew,hasbroadenedtherangeofpossibleexperimentsandmadehyperscanninglesscumbersomeand,asaconsequence,muchmorepopular. EngagementMatters Beyondthepracticalchallengesofinteractiveneuroscience,amorephilosophicalquestionhascirculatedastowhethertheneuralinformationobtainedfrommeasuringpeopleduringsocialinteractionissignificantlydifferentfromscanstakenwhenpeoplearealoneoractingsimplyasobservers.Doesitmatterifthepersonyoulookatlooksback?Isthereadifferencebetweenspeakingasentenceandspeakingittosomeonewhoislistening? Yes,apparentlythereis.Theevidenceisgrowing,sayspsychiatristandsocialneuroscientistLeonhardSchilbachoftheMaxPlanckInstituteofPsychiatryinMunich,that“socialcognitionisfundamentallydifferentwhenyou’redirectlyengagedwithanotherpersonasopposedtoobservinganotherperson.” Demonstratingthosedifferencesdoesnotnecessarilyrequirestudiesofmorethanonebrainatatime,butitdoesrequirerelativelynaturalisticexperimentsthatarechallengingtodesignwithintheconstraintsimposedonstandardlaboratoryprotocols.PsychologistElizabethRedcayoftheUniversityofMarylandstudiessocialinteractioninautism,withafocusonmiddlechildhood.Backin2010,whenshewasapostdoctoralfellowworkingwithRebeccaSaxeattheMassachusettsInstituteofTechnology,Redcaysetupapioneeringexperimentfeaturingoneparticipantinsidethescannerandanother(actuallyaresearcher)outsideitinteractinglivethroughavideofeed.Recordedvideosofanotherinterlocutorservedasacontrol.Intheliveversustherecordedinteractions,Redcaysawgreateractivationinbrainareasinvolvedinsocialcognitionandreward. Hersubsequentstudieshavecontinuedtoestablishdifferencesinthewaytheinteractingbrainresponds.Inchildren’sbrains,moreoftheregionsinvolvedinthinkingaboutthementalstatesofothers—mentalizing,inthevernacular—areengagedwhentheybelievetheyareinteractingwithapeerthanwhentheyarenot.Instudiesofjointattention,acriticalcomponentofsocialinteraction,Redcayfoundthatthementalizingregionsofthebrainsuchasthetemporalparietaljunctionrespondeddifferentlywhensharingattentionratherthanwhenlookingatsomethingbyoneself.Nowshewantstoknowiftherearefurtherdifferencesinhowthebrainsofindividualswithautisminteract.“Istheextenttowhichpeopleengagethosementalizingregionsrelatedtotheirsuccessesinasocialinteraction?”shewonders.Itistoosoontosay,butclearly,saysRedcay,“you’renotgettingthefullstoryifyoujustrelyonobserverapproaches.” Schilbachhasbeenoneoftheforemostproponentsofwhathecallssecond-personneuroscience.Hisstudieshaveincludedvirtualcharacterswhoseemtorespondtoaparticipant’sgaze.Insuchsituations,“theso-calledmentalizingnetworkandtheaction-observationnetworkseemtobemuchmorecloselyconnected[thanweknew],”Schilbachsays.“Theyinfluenceeachother,sometimesinacomplementaryandsometimesinaninhibitoryfashion.”Schilbachhasalsofoundthatevenverysimpleactssuchasgazingatanotherindividualandbelievingtheyaregazingback—aninteractioninwhichyousensethatyourownbehaviorhasaneffectonanotherperson—spursactivityinthebrain’srewardcircuitry,particularlytheventralstriatum.Andthemorerewardingwefindabehavior,themorelikelywearetorepeatit. TheEyesHaveIt Whatishappeningintheotherperson’sbrain?Eyecontactwasalogicalplacetolook.Makingeyecontactactivatesthesocialbrainandsignalstoanotherpersonthatyouarepayingattention. Itisonewayweshareintentionandemotion. NorihiroSadatooftheNationalInstituteforPhysiologicalSciencesinJapanandhiscolleaguesusedhyperscanningtoshow,earlyin2019,thateyecontactpreparesthesocialbraintoempathizebyactivatingthesameareasofeachperson’sbrainsimultaneously:thecerebellum,whichhelpspredictthesensoryconsequencesofactions,andthelimbicmirrorsystem,asetofbrainareasthatbecomeactivebothwhenwemoveanypartofthebody(includingtheeyes)andwhenweobservesomeoneelse’smovements.Thelimbicsystem,ingeneral,underliesourabilitytorecognizeandshareemotion.Inotherwords,itiscriticaltoregulatingourcapacityforempathy. Thetaleswetelleachotherareanidealmeansofexploringthesocialgluethatbinds.NeuroscientistUriHassonofPrincetonUniversityconductedseminalexperimentsinbraincouplingbyusingstorytelling.Inonesuchstudy,heputanindividualinascannerandhadthatpersontellastory.Thenheputsomeonenewinthescannerandhadthevolunteerlistentoarecordingofthestorytoldbythefirstperson.Hassoncomparedthebrainprocessingofspeakerandlisteneracrosstime,matchingactivitymomentbymoment,andhefoundevidenceofthetwobrainscoupling.“Thebrainofthelistenerbecomessimilartothebrainofthespeaker,”Hassonsays.Andthemorealignedthebrainswere,thegreaterthelistener’sreportedcomprehension.SaysHasson,“Yourbrainasanindividualisreallydeterminedbythebrainsyou’reconnectedto.” HassonhasrecentlyjoinedforceswithDartmouth’sWheatleytoseeiftheycanmeasurebrainscouplingduringconversation.Agoodconversation,saysWheatley,means“creatingnewideastogetherandexperiencesyoucouldn'thavegottentoalone.”Shewantstoseethatexperienceinthebrain.Theirstudyincludesscannersatdifferentuniversitiesconnectedonline.(Mostpsychologydepartmentsonlyhaveonescanner.)Withonepersonineachscanner,thesubjectscompleteastorytakingturns—oneparticipantuttersafewsentences,andtheotherpicksupwherethecompanionleftoff.Ifthescientistscancapturebrainstatesduringthisinteraction,Wheatleysays,theymightbeabletoseehowtwobrainsalternatelygetcloserandthenmoveapartfromeachotherduringconversation. BeyondPairs Perhapsinevitably,neuroscientistshavemovedtostudyingnotjusttwo,butmanybrainsatonce.TheseexperimentsrequiretheuseofEEGbecauseitisportable.Earlystudiesshowedthatwhenweengageingroupactivitieslikeconcertsormovies,ourbrainwavesbecomesynchronized—theaudience’sraptattentionmeanstheyprocessthesymphonicfinaleoraloveorfightsceneinthesameway.Thatisnotallthatsurprising,butnowscientistsareapplyingthesameapproachinclassrooms,wherethefindingscouldaddtowhatweknowabouthowstudentslearnbest. InaseriesofstudiesinNewYorkCityhighschools,ateamofNewYorkUniversityresearchersincludingPoeppel,SuzanneDikkerandIdoDavidescotookrepeatedEEGrecordingsfromeverystudentinabiologyclassoverthecourseofasemester.Theyfoundthatstudents’brainwavesaremoreinsyncwitheachotherwhentheyaremoreengagedinclass.Brain-to-brainsynchronyalsoreflectshowmuchstudentslikeeachotherandtheteacher—closerrelationshipsleadtomoresynchronization.Theircurrentstudyisexaminingwhetherlevelsofbrainsynchronyduringclasspredictretentionofmateriallearned.“Ithinkwhatwe’redoingisveryuseful,”Poeppelsays.“How[dowe]usethesetechniquesinatargetedwayforSTEMlearning?” Schilbachbelievesinteractiveneurosciencehasreal-lifeapplicationsinpsychiatryaswell.Itcouldmakeitpossibletopredictwhichtherapistwillworkbestwithwhichpatient,forexample.Andthefocusonreal-lifesituationshelpsensurethatanyfindingshavevalueforpatients.“Asapsychiatrist,”Schilbachsays,“I’mnotinterestedinhelpingapersontogetbetteronaparticularsocialcognitivetask.I’mtryingtohelpthatpersontoleadahappyandsatisfyinglife.” Rights&Permissions ABOUTTHEAUTHOR(S)LydiaDenworthisaBrooklyn,N.Y.–basedsciencewriterandacontributingeditorforScientificAmerican.ShewroteabouttheneuroscienceofstutteringinourAugust2021issue.Sheisco-authorofParentNation. Credit:NickHigginsRecentArticlesbyLydiaDenworthHowToTreatCOVIDatHomeCan'tBuyMeLuck:TheRoleofSerendipityintheBeatles'SuccessEpstein-BarrVirusFoundtoTriggerMultipleSclerosisReadThisNextReproductionToBetterUnderstandWomen'sHealth,WeNeedtoDestigmatizeMenstrualBloodChristineN.Metz|OpinionPrivacyYes,PhonesCanRevealifSomeoneGetsanAbortionSophieBushwickMedicineHowToTreatCOVIDatHomeLydiaDenworthPollutionDeclinesinAirPollutionHaveMadeHurricanesStrongerChelseaHarveyandE&ENewsBlackHolesHowAstronomersFinallyCapturedaPhotoofourOwnGalaxy'sBlackHoleSethFletcher,TulikaBoseandJefferyDelViscioEpidemiologyWhatOneMillionCOVIDDeadMeanfortheU.S.'sFutureMelodySchreiberAdvertisement NewsletterGetsmart.Signupforouremailnewsletter.SignUpSupportScienceJournalismDiscovernewinsightsintoneuroscience,humanbehaviorandmentalhealthwithScientificAmericanMind.SubscribeNow!ScrollToTop Supportsciencejournalism.ThanksforreadingScientificAmerican.Knowledgeawaits.SeeSubscriptionOptionsAlreadyasubscriber?Signin.ThanksforreadingScientificAmerican.CreateyourfreeaccountorSignintocontinue.CreateAccountSeeSubscriptionOptionsContinuereadingwithaScientificAmericansubscription.SubscribeNowYoumaycancelatanytime.Signin.