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