A Skeptic Considers the Hype over Brain Cells Linked to Complex Behavior.docx

A Skeptic Considers the Hype over Brain Cells Linked to Complex Behavior.docx

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ASkepticConsiderstheHypeoverBrainCellsLinkedtoComplexBehavior

ASkepticConsiderstheHypeoverBrainCellsLinkedtoComplexBehavior[Excerpt]

Are"mirrorneurons,"toutedtogiveustheabilitytoreadtheintentionsofothers,alltheyarecrackeduptobe?

May31,2013 |By RobertA.Burton

St.Martin’sPress

Editor'snote:

Thischapterfrom ASkeptic’sGuidetotheMind byRobertA.Burton（SaintMartin’sPress,April23,2013） relatesthatoneofthemost-heraldeddevelopmentsinneuroscienceinrecentyears—thediscoveryof“mindreading”mirrorneurons—failstoliveuptotheassertionsofsomeresearchersthatthesebraincellsaffordprofoundinsightsintotheintentionsofanotherindividual.

Excerptedfrom ASkeptic’sGuidetotheMind:

WhatNeuroscienceCanandCannotTellUsaboutOurselves,byRobertA.Burton.Copyright©2013.AvailablefromSaintMartin’sPress.

TalkinginTongues

Theoriginalisunfaithfultothetranslation.

—JorgeLuisBorges,concerningthe

Vathek,byWilliamBeckford

Therecentsurgeinthepublicinterestinneuroscienceislargelydrivenbythehopethatscientificinvestigationcanprovideuswithabetterunderstandingofhumannaturethanpreviouspsychology-basedtheories.Butthebasiclanguageofpresent-dayneurosciencecan’tprovidethisunderstanding.

Itdoesusnogoodtoknow,asdescribedinarecentjournalarticle,thatapersonisexperiencing“increasedactivityinregionsofthedorsalanteriorcingulatecortex,thesupplementalmotorarea,anteriorinsula,posteriorinsula/somatosensorycortex,andperiaqueductalgrayandthatthetemporo-parietaljunction,theparacingulate,orbitalmedialfrontalcorticesandamygdalawereadditionallyrecruited,andincreasedtheconnectivitywiththefrontalparietalnetwork.”

Suchprofessionaljargonisessentiallyincomprehensibleandmeaninglesstoallbutaselectfew.Justasweneedatranslatortotelluswhat’swrittenonanancientSanskritpapyrus,neuroscientistsmusttranslatetheirarcanetextsintoareadilyunderstandablecommonlanguage.Theymusttellusthattheseregionsofthebrainconstituteapainmatrixandthattheseneuralstructuresareinvolvedinourpersonalexperienceofpain.Asaconsequence,neuroscientistsmustweartwoseparatehats—investigatorandtranslator.Theyplytheirtrade,forwhichtheyhavebeentrained,andthentakeonthesecondroleoftranslatorandexplaineroftheirowndata.Unfortunately,thisbringsusbackfullcircle;neuroscientistsmusttranslatetheirfindingsintothelanguageofpopularpsychology.

Theinherentdifficultiesinassumingthisdualroleofexperimenterandtranslatorcannotbeoverstated.Basicneuroscienceisahighlycomplexanddifficultfield;mostneuroscientistshavearelativelynarrowfieldofrealexpertise.Withtensofthousandsofcognitivescientistschurningoutnewinformation,keepinguptodateisamonumentaltask.Forbasicscientiststoalsobewellinformedinpsychologyisimpossible.Nothavingthetime,andoftenlackingthebackground,training,orinterest,theymust,toexplaintheirfindings,relyonpopularpsychologicaltheoriesthattheyareoftenill-equippedtojudge.Experimentalpsychologyisafielduntoitself.Yearsofstudyarenecessaryinordertoachieveevenasuperficialunderstandingoftheinnumerablepitfallsofexperimentaldesignandinterpretation.

Similarly,psychologists,cognitivescientists,andphilosophersincreasinglyincorporatesummaryconclusionsofneurosciencetosupporttheirideas,butwithouthavingthetrainingtorecognizeinherentlimitationsofbasicsciencemethodsandinterpretations.Thecycleisnever-ending.Newpsychologicaltheoriesbecometheneuroscientists’languagefortranslationoftheirownbasicsciencedata,whichinturnarecitedbythepsychologistsasevidencefortheirtheories.Onceanideagetsafootholdinthecollectivemindofthecognitivesciencecommunity,itdevelopsalifeofitsown,irrespectiveofitsunderlyingvalidity.Unsubstantiatedword-of-mouthmorphsintohardfact.

Togiveasenseoftheinherentlimitationsoftranslatingharddataintothepopularvernacularoffolkpsychology,I’vechosenafewhighvisibilitysubjectstoconsider.

Mygoalisn’ttopickapartindividualfindings,asthisisn’tparticularlyhelpfulinabroadercontext.Norisittolaunchpersonalattacksonthemostlywell-meaningscientists.Rather,I’dliketoofferamorepracticalwaytoassessthequalityofanyneuroscienceclaim.Insodoing,Ihavepickedoutarticlesthatarelikelytohavesignificantinfluenceonourfutureunderstandingofaspectsofbehavior,rangingfromempathyandintelligencetofreewillanddeterminationofconsciousness.Mygoalisn’ttorefutetheobservationsbuttoquestionthedegreeofconfidenceintheconclusions.Let’sbeginwiththediscussionofmirrorneurons.

ReflectingonMirrorNeurons

        Inthelate1980s,ItalianneuroscientistGiacomoRizzolattiandcolleagueswerestudyingthepremotorregionofthefrontallobeofamacaquemonkey.Usingintracellularelectrodes,theywereabletolocateandrecordtheelectricalactivityofindividualcellsthatfiredwhenthemonkeyreachedforbitsoffood.Asthestorygoes,onemonkeywasrestingbetweenstudies,intracellularelectrodesinplace,justwatchinghisexperimenters.Whenoneoftheresearchersreachedoutandpickedupapeanut,thesamecellsbeganfiring,asthoughthemonkeywerereachingforthefood.Rizzolattipainstakinglydeterminedthatthisregionofthebraincontainedcertaincellsthatwouldfirewhenthemonkeyperformedasinglehighlyspecifichandactionsuchaspulling,pushing,tugging,grasping,pickingup,orputtingapeanutinitsmouth,andthatthesesamecellswouldfirewhenobservinganotherperformingthesameaction.Itwasalsonotedthatthemovementhadtoappearintentional—asthoughthehandwasreachingtograspthepeanutinordertoeatit,ratherthanmerelymakingthesamegesturewithouttheexperimenterintendingtoeatthepeanut.Giventheircombinedcapabilityofrecordingtheobservationofanactionandinitiatingtheaction,thesecellssoonbecameknownas“mirrorneurons,”andcollectivelyasthe“mirrorneuronsystem.”

It’simportanttoconsiderhowwelearnamotoraction.Imaginetakingupahobbyforwhichyouhavenopriorexperience—celloplaying.Youhavenoideahowtoholdtheinstrument,whereitfitsbetweenyourlegs,howtomakeasoundwiththebow.Youpainstakinglylearnbyobservingandtryingtoimitatewhatyousee.（Thisistrueforanymotoract,fromcrawlingorwalkingtotalkingortexting.）Thislearningprocess—observationandimitation—isaccomplishedbythecreationofneuralcircuitry:

arepresentationalmapspecifictocelloplaying.Eachtimeyouwatchyourteacherplay,thecellocircuitisenhanced.Eachtimeyoupractice,itisenhanced.Ifyouhadelectrodesplacedwithinyourcellocircuitry,youwouldbeabletoseeincreasedactivityunderbothconditions.Learningtoplayaninstrumentistheactoftryingtosynchronizewhatyou’veobservedwithwhatyouareactuallydoing.

Let’sthrowinafewmoredetails.Yourteacher’scelloisoldandhasawonderfulfragrance.Asshetakesitoutofitscase,youarevividlyremindedofthathighschoolfieldtriptohearyourfirstconcert.Afterward,youweretakenbackstageandgivenademonstrationofthevariousstringinstruments.Yourememberholdingseveralveryoldviolinsinyourhand,evensniffingthemandenvisioningwhatitwouldhavebeenliketoplaythemwhentheywerenew.YourteacherquicklysnapsyououtofthisbriefreveriebyplayinganexquisitepassagefromaBachprelude.Toyoursurprise,andcompletelyoutofcharacter,youwellupwithtears.Youcomplimenther,butinsteadofbeinggracious,shesternlyremindsyouthatwhenshewasyourage,shepracticedeighthoursaday.Yourtearsevaporateasyoushiftgearsandwonderhowanyonecoulddevoteherlifetorubbingdriedhorsehairacrossafewstrandsofcatgutwhenshecouldbeoutplayingballortweetingherfriends.

NowimaginethisbriefscenariotakingplacewhileyouarewearingaportablefMRIscanner.Mostofuswouldexpecttoseeincreasedactivityinareasofthebraininvolvedinmotorperformance,observationofanother’smotoractions,processingofsmells（olfactoryregions）,areasactiveinmemorystorageandrecall,andtheexperienceofvividemotions.Anycomplexneuralcircuit,whetheritrepresentscelloplayingorProusttastinghisfamousmadeleine,functionsbycoordinatingtheactivityofanumberofbrainareas.Lumpedtogetherinthiscircuitryarebothourobservationsofanactionandtheacquiredmotorskillstocarryoutthisaction.

Asimplifiedschemaforlearninganaction:

Observation→DetailedTemplate（representationalmap）thatisstoredinmemory.Overtime,aslearningproceeds,theneuralsubstratefortheobservationandtheactionmergeintoasingleobservation/actionrepresentationalmapnecessarytocarryoutthelearnedaction.

Rizzolatti’sfindingofacombinedobservation/actionsystem（thesameneuronsfirewhenamonkeyreachesforapeanutaswhenitobservestheexperimenterreachingforapeanut）confirmsatthecellularlevelwhatwealreadysuspectedatacommonsenselevel.Whatcouldnothavebeenanticipatedwasthedegreeofexcitementhisdiscoveryhasgenerated.Inthesubsequenttwodecadeshisworkhasbeenpositedasthebiologicalbasisforhowwereadmindsandexperienceempathy.Buthowmuchofthisspeculationisjustified?

Bytracingtheevolutionoftheallegedimplicationsofmirrorneurons,wecangetasenseofsomeoftheinherentproblemsoftranslatinggoodbasicneuroscienceintobehavioralexplanations.

Shortl