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Download Class 8 Computer Science books, solutions, latest solved sample papers and question papers, syllabus and many other useful study material. Students can free download study material in pdf which has been prepared based on latest guidelines, term examination pattern. Download all the materials mentioned in those boxes – plus quite a few extra ones I’ve thrown in for good measure - from the links in this document. Please feel free to share all these resources with colleagues, students, trainees and clients.

Download all the materials mentioned in those boxes – plus quite a few extra ones I’ve thrown in for good measure - from the links in this document. Please feel free to share all these resources with colleagues, students, trainees and clients.

NANCY KANWISHER:Beforewegetontothetopicfortoday,IfeltlikelastMonday'slecturewasnotmybest.Idon'tknowwhy.It'snotthatIdidn'tputtimeonit.IlookedandIhadthewronglecturenumbersonslides.Therewasallkindofchaos.I'msorryaboutthat.Sometimesyouputinalotofeffort,andyoustillgivealecturethatisn'tallthatclear.

Brain Surfing is a fantastic combination of some of my favourite topics: travelling and marketing / advertising strategy. I always enjoy meeting fellow strategists around the world with whom I have interesting and enriching conversations over coffee, so this is like a concentrated expresso drip version of coffee meeting goodness in one book I. Anatomy of the Brain. The brain consists of the brain stemand the cerebral hemispheres. The brain stem is divided into hind-brain, mid-brain and a ‘between-brain’ called the diencephalon. The hind-brain is an extension of the spinal cord. It contains networks of neurons that constitute centres for the control of vital.

SoletmetrytotellyouwhatIthoughtwerethemainpoints.Istartedoffbysayingwhyit'sreallyfundamentallyimportanttobeabletounderstandnotjustwhatpeoplelooklikefromtheoutside,butwhatwereallycareaboutpeopleiswhat'sgoingontheinsideabouttheirthoughtsandtheirbeliefs.Andweareconstantlymakinginferencesaboutwhatpeopleknow,andbelieve,andwant,andthink.

Andwedothatallthetimetounderstandwhythey'redoingsomethingandtopredictwhatthey'lldonext.Andsoit'sfundamentallyimportant.It'stheessenceofbeingahumanbeinginmanyways.It'stheessenceofliterature.Andwedoitallthetime.

Andaclassicwaythatpeoplehavestudiedfalsebeliefsis--orthinkingaboutotherpeople'sthoughtsiswiththefalse-belieftask--theSally-AnnetaskthatIdescribed.Andthereasonpeopleusethefalse-belieftaskratherthanjustabelieftaskisifthebeliefsaretrue,youcananswerwhatsomebodywilldobasedontheworld,notbasedontheirmind.Andso tounconfoundthetwo,weuseafalsebeliefthat'sdifferentthanthestateoftheworld.Sowecanbesurewe'reaskingpeoplewhatwillhappennextbasedonwhatthatpersonbelieves.

AndthroughdecadesofuseoftheSally-Annefalse-belieftaskandvariationsofit,it'sclearthatthere'saverydistinctivedevelopmentaltimecourseandabilitytosolvethisproblem.Five-year-oldssolveitnoproblem.Three-year-oldssystematicallyfail.Andpeoplewithautismtypicallyget--passthistasklateornotatall.High-functioningpeoplewithautismpassthetask,justlater,like7,8,9years,notfiveyearsold.OK?

Sothat'sthekindofbehavioralbackgroundevidencethatthere'ssomethingdistinctiveaboutthinkingaboutotherpeople'sminds.Thenweconsideredwhetherthere'sspecialbrainmechanisms.AndIarguedthat,yes,there are.There'sabunchofthem.ButthemostimpressivelyselectiveoneistheTBJshownupthere.

Andtheevidencethatit'sspecificallyinvolvedinthinkingaboutotherpeople'sthoughtscomesfromthefactthatthatactivationisagreateractivationwhenyouthinkabout--whenyousolvethefalse-belieftypeproblems,whenyouthinkaboutanotherperson'sthoughtscomparedtowhenyouthinkaboutarepresentation,aphysicalrepresentation,likeaphotographoramap,OK?Sothosearelogicallyisomorphicproblems.Wehavetoalwaysansweraquestionaboutarepresentation.It'sjusttherepresentationisinsomebody'sheadorit'saphysicalrepresentationintheworld.Andinthatdifference,yougetthatregionofthebrain,OK?

Sothat'scoolbecauseit'saverynicelydesigned--it'snotquite a--nothing'saminimalpair,butit'saminimalpairinsomerespects,right?Itcarvesoutwhethertherepresentationismentalorphysical,butitdoesn'tsolveeverything.Andasuiteofothertaskshaveshownthat thatregionisactuallyspecificinawholebunchofotherrespects.

Itdoesn'trespondjustwheneveryouthinkaboutaperson.Thereareexternalproperties.Andmostimpressively,itdoesnotevenrespondwhenyouthinkabouttheirvisceralbodysensations,likethirst,andhunger,andpain.

SotheTBJdoesn'trespondtojustthinkingaboutanymentalstatesofanotherperson.It'sspecificallythinkingabouttheirthoughtsandbeliefs.Andthat'sprettydamnremarkable,right?It's,howabstractcanyouget?Andyet,here'saspecificbrainregionforthatveryabstract,veryspecificthing.

AndthefinallittlebitofevidenceIshowedyouisthatitalsogeneralizes.It'snotjustaboutlanguagebecauseyoucanshowpeoplemoviesthathavenowordsinthembutthatclearlyshowcharacterswhomustbethinkingabouteachother'sthoughts.Andinthosemomentswhenthecharactersarethinkingabouteachother'sthoughts,thatregionturnson,more,forexample,thanwhenthey'rethinkingabouteachother'spain,OK?

Yeah.

AUDIENCE:Didsomebodylook atwhathappensifotherpeoplethinkaboutme?OrifIthinktheythinkingaboutme?

NANCY KANWISHER:Youmeanifyou'rethinkingaboutotherpeoplethinkingaboutyou?

AUDIENCE:Yeah,exactly.

NANCY KANWISHER:Yeah,Iwouldassumethatthatregionwouldbeengaged.I'msuretherearestudiesonthat.Becauseyou'rethinkingabouttheirthoughts,right?

AUDIENCE:Butmore?Isitmoreinteresting?

NANCY KANWISHER:Probablyjustbecauseit'smoresalient,right?Iactually,oddly,inthisclass,Italkaboutattentionattheend,whichisweirdbecauseattentionisanissuewitheverystudy.Butmostofthebrainregionswe'vetalkedabout,surely,includingthisone,aremodulablebyhowstronglyyou'reattendingtosomething.Soifsomething'sreallysalient,orimportant,oryou'rereallypayingalotofattentiontoit,you'regoingtogetmoreactivation.Andifit'smoreinterestingtothinkaboutwhatotherpeoplethinkaboutmethantothinkaboutwhatotherpeoplethinkabouteachother,you'llfindsomemodulationinhere,I'msure.

OK,andthenfinally,Italkedaboutmoralreasoningasatestcase.It'snotthattheTPJisselectivelyinvolvedinmoralreasoning.It'sthatmanyofthecriticalaspectsofmoralreasoningdependonwhatapersonknewatthetime.Andsotousethatinformationinmoralreasoning,youneedtopullthatregionin.

SoIrealizedIwrotethatquestionambiguouslyonthequiz.Imeanttoask,istheTPJengagedspecificallyoronlyinmoralreasoning,towhichtheyanswer--thecorrectanswerwouldbeno.ButIdidn'tputthe'only'inthere.AndIdecideditwasambiguous,soifyousaid'yes,'yougotthepoints.

Anyway,Igaveseveralbitsofevidencethat,usingthemoral-reasoningcase,thattheTPJis--it'sstrongerevidenceit'sinvolvedinthinkingaboutotherpeople'sthoughts,first,thatweshowedthatpeoplewithautismwillhavethisdifficultyinthinkingabouteachother'sthoughts.Evenoncetheycanpassthefalse-belieftask,theyputlessemphasis,lessweightonwhatthepersonknewatthetimewhenevaluatingthemoralstatusoftheiractions,OK?

It'snotthattheymakeamistakeorthatthey'reunabletomorallyreason.It'saprettysubtlething.It'sjustasmalldifferenceinhowmuchtheyweighwhatanotherpersonknewatthetime,OK?

That'salsoknownaslessforgivenessorlessexonerationforaccidentalharm,right?Youkicksomebodybyaccident,andtheygoouch,well,maybeyougetalittlebitofblamebecauseyouwereaklutzandyoushouldhavethoughtorsomething.Butitwasanaccident,soyoushouldbeexonerated.Peoplewithautismexonerateslightlyless,right?

OK.SowethentalkedaboutthefactthatifyouzaptheTBJwithTMS,stickacoilthere,youdothesamething.Youslightlyreducetheweightpeopleputonwhatthepersonknewatthetimeintheirmoralevaluationoftheperson'sactions.AndthenIshowedthisbizarrefactthat,asIthinkGisellaasked,well,shouldn'ttheTBJbedifferentinpeoplewithautism?Yes,absolutely,accordingtoallofthis,itshouldbe.Butthebasicunivariatemeasures--howbigitis,howselectiveitis,whereitis--donotfindadifferenceinthatregionwiththatcontrastinhigh-functioningpeoplewithautism.

That'ssurprising.Butonepossibleanswertothatiseventhoughit'sthereandit'sjustasbigandstrongandallofthat,it's--thatdoesn'tmeanitdoesn'trepresentdifferentinformation.AndIshowedyouanexamplethatintypicalpeople,youcandecodefromtheTPJwhetherthepersonisreadingaboutanotherperson'sintentionalharmoraccidentalharm.Andyoucan'tinpeoplewithASD.OK?Sothat'smysummaryoflasttime.

Andthenallofthatwasfocusingveryparticularlyonthemostfancy,quintessentiallyhumanaspectofsocialcognition,whichisthisbusinessofrepresentingeachother'sthoughtsandbeliefs.ButIpointedoutattheendthattherearealsolotsandlotsofotherfacetsofsocialperceptionandsocialcognition,manyofwhichhavesomewhatselectivebrainregions,lotsofthemotherpartsofthebrain,andwejustdidn'thavetimetofiltratein tothat,OK?HopefullythatwasalittlebitclearerthanIwaslasttime.

OK,so,sofar,inthiscourse,we'vebeenfocusingonallthesebitsofbrainthatseemtodoverydistinctive,oftenveryselectivethings,OK?Sotheonewe'vejustbeentalkingaboutisthatlittleguyrightthere.Butwe'vetalkedaboutalotofthesethingsinhere.

Andthefieldofhuman-cognitiveneurosciencehasinvestedlotsofefforttofindthesethingsandtrytocharacterizewhateachofthemdoes.Andthat'sprettycool,right?Thisisallstuffwedidn't know20yearsago,andit'snice,anditcountsasrealprogress,Ithink.Butitleaveslotsofthingswoefullyunanswered.

Noneoftheseregionscanactalone,eventhoughI'vedepictedthemin asomewhatsillyfashion,asnicelittleM&Msonthebrain.Noneofthemactalone.Noneofthemcouldactalone.Theyneedinformationtoprocess,sotherehastobeinputtoeachregion.Theyneedtobeabletotellotherregionswhattheyfiguredoutorthere'snopoint.

Andprobably,astheysolveaproblem,astheyconducttheircomputations,they'reprobablyinteractingallthetimewithlotsofotherregions.Sowedesperatelyneedtounderstandnotjustthatthispatchdoesfaces.There'slotsmoreweneedtoknow.And oneofthethingswereallyneedtoknowis,whatisitconnectedto,andwhoisitinteractingwith?OK?OK.Sothat'swhatIjustsaid.

Andsothatmeanslookingatnotjustthecortexthatwe'vebeenfocusingonthroughthiswholecourse,thisdarkmatterthat'sonthesurfaceofthebrainupthere.Buttoday,we'regoingtodoafigure-groundfliponthebrain,andwe'regoingtostartpayingattentiontoallthatstuffthatusedtobebackgrounddownthere,allthatwhitematterunderneath,whichislikeabigheapofmyelinatedfibersthatconnectlong-rangeregionsofthebraintoeachother,OK?

Soyoumightsay,OK,justwires--whocaresaboutthewires?Thatwasmyattitudeforalongtime.I'vegottenoverit.Wedesperatelyneedtoknowaboutthewiresforallkindsofreasons.

SoI'mgoingtogothroughawholebunchofreasons.Andthere'salotoflittledetails,andIdon'twantyoutopanic.Ijustwanttogiveyouthegistofwhythisisworthpayingattentionto.

OK,sofirstofall,whitemattermakesup45%ofthehumanbrain.Sothatalonetellsyouit'snotlikesometrivialthing.It'sabigpartofyourbrain.Thisisallthemoreinterestingbecausethat'snottrueinotheranimals.

SoIthinkwhitemattermakesupahigherpercent ofthehumanbrainthananyotheranimal,oratleastwe'rewayupthere.Inmice,it'sonly10%.Andmaybethat'sarelativelyuninterestingthingaboutscalingwithbrainsize,butmaybeit'ssomethingdeeperabouthumanbrain--what'sspecialaboutthehumanbrainandnobodyknows.Andhere'safunfact.Ifyoutookallthemyelinatedfibersinthehumanbrainandyoulaidthemoutendtoend,youcouldgoaroundtheworldthreetimes.Sowe'vegotlotsofcableagesittinginhere.

OK.SoIbrieflyarguedbeforethatyousimplycannotunderstandthecortexwithoutunderstandingitsconnectionsofoneregiontoanother.It'sjustcrazytostudyonelittlepatchofthebrainandnotknowwhoit'stalkingtoandwhereitgetsitsinputsfrom.AndasIjustsaid,thepressingneedforthatknowledgeisheightenedbythepresenceofthismap,whichwedidn'tusetohave.Nowthatwehavethismap,it'sallthemoreimportantandpressingtoknowwhattheconnectionsofthoseregionsare.

OK.Sohere'sanicequotemakingthispoint.ThisisHeidiJohansen-BergandMattRushworth.Theysay,'Connectivitypatternsdefinefunctionalnetworks.Theinputstoabrainregiondeterminetheinformationavailabletoit,whereasitsoutputsdictatetheinfluencethatbrainregion cancanhaveonotherareas.Therefore,simplybyknowingthepatternofinputsandoutputsofabrainregion,wecanbegintomakeinferencesaboutitslikelyfunctionalspecialization.'

So I thinkthat'sanicequote.Itmakesthepointthatit'snotjustthatweneedtoknowtheconnections,buttheconnectionsandthefunctionareboundtobedeeplyenmeshed.Oneconstrainstheother.Yeah?OK.

Further,recallwayback,whichwillquitepossiblyreturnonthefinalexam--howdowedefineacorticalarea?Igaveyoucriteriaforacorticalarea.Andoneofthecriteriawasadistinctivepatternofconnectivity,right?Soit'spartoftheidentifyingpropertiesofacorticalareaiswhatit'sconnectedto.Andsothat'sanotherreasonweshouldcare.

Athirdreasonisifweknewofagivencorticalareawhatitslong-rangeconnectionsweretolotsofotherregions,thatconnectivityfingerprint--rememberwetalkedbrieflyaboutconnectivityfingerprintsamonthorsoago?Thatfingerprint,thedistinctivesetofconnectionsofthatregion--youcanthinkofitasasignatureofnotjusthowthatregiondiffersfromotherregionsinthatsameindividualbrainbuthowwemightfindahomologofthatregioninanotherspecies.Andthatwouldbeaveryinterestingthingtodo.

Wouldn'titbecooltoknow,isthereaTPJinmacaques?Well,macaquescan'tsolveananalogofthetheory-of-mindtask.Chimps--wecoulddebatealittlebit.Andnarrowdomains--kindofsortof,alittlebit,notreally.Macaques--no,OK?

Soisthereahomolog?Isthereacorrespondingregionthat--maybewetookthatregion,andweadapteditandmadeitworkbettersowecoulddobetterthingswithit?Andifso,whatisitdoinginmacaques,right?Imean,Ithinkthat'sjustatotallycoolquestion.

Andinprinciple,onewaytosaywhatcountsas'thesameregion'acrossspecies,whichiskindofaweirdquestion.They'redifferentspecies,sowhatwould'thesameregion'mean?Onewaytosaywhatthesameregionmeansistohaveasimilarconnectivityfingerprint,OK?Sothereareseveralstudiesthattrytodothat.Icouldn'tcramthemintothislecture,butifyou'reinterestedinreadingonit--readingaboutit,shootmeanemail.I'llsendyousomepapers.OK.

Ialsomentionedthatthespecificsetofconnectionsofacorticalregion,particularlyitsinputs,playanimportantroleindevelopment.Remembertherewiredferrets?Ifyouredirecttheinputtowhatwouldhavebeenprimaryauditorycortexinaferretandyouhavethatinputcomeinfromtheeyes,youcangetwhatwouldhavebeenprimaryauditorycortextobecomealotlikeprimaryvisualcortex.

Soconnectivityisimportant,notjustinhowaregionfunctionsandhowwesaywhatcountsisthesameacrossspeciesbutisprobablyalsocruciallyimportantinthedevelopmentofregions,OK?Ialsoshowedyouevidencethatthevisualword-formarea--wecanpickoutexactlywhereit'sgoingtolandinanindividualbrainbytheconnectivityfingerprintofthatregionbeforekidslearntoread,furtherevidencethatconnectivitydetermineslaterfunction.

OK.Asifthisisnotenough,otherreasonstocareaboutwhitematteristhatdisruptionsofwhitematterareattherootofmanyclinicaldisorders--dyslexia,autism,developmentalprosopagnosia,amusia,allofthesethingsandothers,forallofthem,disruptionsinlong-rangewhite-matterconnectionshavebeenimplicatedaspossiblyplayinganimportantroleintheetiologyofthatdisease.

Aging--mostdefinitelydeclineinwhitematterisprominentinaging.Sorrytosay,there'sa10%decreaseinwhite-matterfibersperdecadestartingatage20.Useyoursnowwhileyouhavethem.Let'schangethetopic.OK.

There'salotoftalkabouthowwhite-matterconnectionsmaychangewithexperience,andlearning,andplasticity.Andthat'saprettypatchyliterature.Andit'snotaveryimpressiveliterature.

Theclassicthingyouprobablylearnedin9.00,thatwhenyoujuggle,yougetchangesinwhite-matterconnectionsfromjugglingexpertise.Maybe.Maybenot.There'ssomeproblemswithalotofthatliterature.Soit'saninterestingquestion,butit'snotclearwhatthestronganswersare.

Andfinally,Idon'tknowaboutcircuitdesign.Probablysomeofyoudo.ButIgatherthatpeoplewhothinkalotaboutcircuitdesign--oneofthekeyfeaturesyouneedtotakeintoaccountiswiringlength.Youwanttokeepwiringlengthshort,right?

Youhaveconductiondelays.Youhaveheating.Youhavespacetakenupincircuits.Allofthosethingsarebadincircuitdesign,andthey'rebadinbraindesigntoo.

Soalotofreasontothinkthatamajorfactorinthedesignofbrains,especiallyhumanbrains,isminimizingwiringlengthbecausewiringlengthisveryexpensivemetabolically.You'vegottomaintainiongradientsacrosscellmembranes.It'sexpensivedevelopmentally.Thesedamnthingsneedtofigureoutwheretogo,andiftheydon'tgototherightplace,youhaveadevelopmentaldisorder.

Andsoit'sprobablyarealconstraintondesignsofbrains.OK,sothatwasawhirlwind--lotsofreasonstocareaboutwhitematterandconnectivity.Oh,plus,atleastinanimalresearch,there'sawholesuiteofamazingnewmethodsforlookingatconnectivityinanimalbrains.And[INAUDIBLE]cantellusmoreaboutthatthanIcouldbecauseshe'sworkinginalabthat'srightattheforefrontofdevelopingthosemethods.Someday,we'regoingtoapplythosemethodstoahumanbrain--Ican'twait--andgetthewholewiringdiagram.OK.

Anyway,sowhatdoweknowabouttheconnectivityoftheseregions?Well,youmaybethinking,don'twealreadyknowallthisstuff?Afterall,Ishowedyouthisdiagramwayback.Andyou'veprobablyseeniteverydamncourseyoutakeinthisdepartment.It'sinmosttextbooksinthefield--thewholewiringdiagramofthevisualsystem.

Sodon'twealreadyknowallthisstuff?Sowhat'sthebigdeal?Well,here'sthebigdeal.That's amacaquebrain.Andinmacaquebrain,youcangettheactualanswertowhatistheactualstructuralconnectivityofthispatchofcortextothatpatchofcortex.

There'sawholebunchofmethods,buttraditionally,youinjectsomedyeherethat'suptakenbyneuronsthattravelsalongaxonsthatgoeshere.Youkilltheanimal,sliceupthebrain,andfindthattraceroverhere.Andthenthosetwothingsareabsolutelyconnected.That'sthegoldstandard.Andthat'sthebasisofmostofthosestudies,thatmethodandvariationsthereof.

Butwecan'tdothatinhumanbrains.Andsowedonothaveanythinglikethisinformationinhumanbrains.Yes,David.

AUDIENCE:Whenwasthisdone?

NANCY KANWISHER:Oh,thatisacompilation.Thiswaspublished,in,Ithink,1991.Butthatwasacompilationofheapsofstudiesthathavebeendonebeforethat.Itwasabigreviewarticlelookingatallofthisliterature,wherelotsofclassicneuroanatomypeoplewoulddothesethingswheretheywouldinjecttracers,andsliceupbrains,andlookinotherplaces.Anditwasjustavastamountofliteraturethatdidthatformanydecades.It'ssortoffallenoutoffavor,eventhoughthesethingsare,atleast--Idon'tknow--thesearereallycrucialquestions.

Nowpeopleuseothermethodstodothat.Youcanuseallkindsofoptogeneticandothermethodstomapconnectivityinanimals.Yeah.

AUDIENCE:I have aquestion.

[INAUDIBLE].

NANCY KANWISHER:Inhere?Oh,that'sagoodquestion.Oh,it'sprobablydorsalandventralpathways.Letmeseehere.Yeah.

Yeah,theredones--thisisanotherthingIdidn'tevenreallymention,probablyletalonegive ashort[INAUDIBLE].Thatwaslame.Butanyway,thevisual--highlevelsofthevisualsystem--wefocusedontheventralvisualpathwaycomingdownthebottomofthetemporallobe.Butthere'sawholeothervisualpathwaythatgoesupintotheparietallobe.

DidItalkaboutthatalittlebit--reachingandgrasping?No,Ididn't.Lame,lame,lame,lame.Anyway,amajorpartofthefieldIdidn'tgetto.

Anyway,it'sawholeotherpartofthevisualsystemthatseemstobemoreinvolvedinvisuallyguidedaction.Andthey'reactuallyveryinterconnected,butthey'retryingtoemphasizethatthedorsalpathwayisatleastsomewhatseparableinmonkeys.Butmypointisthisismonkeyswheretheyhavethegold-standardmethods,andtheycanactuallydiscovertherealconnectivity.

Sadly,wecan'tdothosethingsinhumans.Andinhumans,wehaveonlythreemethods,andnoneofthemareverygood.Sowe'lltalkaboutthemtodayanywaybecausethisissuchanimportantquestion,butthebottomlineis--thisdrivesmeoutofmymind--webasicallydon'tknowtheconnectivityofanyofthoseregionsforsureinhumanbrains.

Andsomebody'sgottosolvethat.Maybeoneofyouwillgoinventamethodthatworksinhumansthathelpsussolvethatproblembecauseit'sactually,Ithink,reallyparalyzingtoourfield.SoI'lltellyouwhatwedoknow,whichisn'tmuch.But,youknow,beggarscan'tbechoosers.

OK,the firstmethodhasbeenaroundforafewyears,andthat'sgrossdissection.AndImeangross,likethatkindofgross--soonlygoodforpost-mortembrains,butit'sreallyquiteamazing.Thisisabottomviewofthebrainbackandfront.

Thisisactuallyaphysicallydissectedbrain.Like,ittakesarealseriousneuroanatomistandlotsoffancymethods--Imean,notfancymethodsbutlotsofcareful,preciseteasingapartofbitsofbrain.Andyoucanactuallyseethesebigfiberscominguphere.

Soifthisisthebackofthebrainandwe'relookinguplikethis,whatdoyouthinkthosefibersareconnectingrightthere?Bigfiberbundlecomingfromdeepdowninthebrainuptorightinthere.

AUDIENCE:Isthatthalamusto[INAUDIBLE]?

NANCY KANWISHER:Bingo.Exactly.OK,sothat'stheLGNrightthere.Andthisiscalledtheopticradiation.It'sthishugecableoffibersthatcomeup.OK,first,here'stheoptictract.

Actually,Iforget.That'snot--Ithinkthisistheoptictractthat'sbeensnippedthere.Thenitcomesupinhere,makesastopintheLGN,andthenthisbigbatchoffiberscomesuprighttheretoprimaryvisualcortex,OK?Everybodygotthat?OK,soyoucanactuallyseeitindissectingadeadbrain.OK,that'sprettycool.

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Butwhatifwedon'twanttowaitforpeopletodie?Often,wewanttoaskquestionsaboutapersonrightnowintheirbrain.Dotheyhavethisdisorder?Aretheyatriskofthatdisorder?Whatistheirconnectivity?

Soforthat,wehavetwomethods,andI'lltalkaboutthesetwomethodsintherestofthelecture.Thefirstoneisdiffusionimaging.OK,soItalkedaboutthisbrieflybefore.Butletmeremindyouofwhatthebasicprinciplesare.

Sohereisapictureoftheopticnervewithabunchofaxonsorientedlikethat.It'sabigcablewithawholebunchoflittlefibersinthere.Andthebasickindofbiophysicsisthatwaterwantstodiffusemorealongthislength,followingtheorientationofthefibers,thanitwantstodiffusethisway,OK?

Anddiffusionimaging--I'mnotexplaininganyofthephysics,butjusttakeitformywordthatwhatdiffusionimagingdoesisgiveyouapictureofthedirectionofwaterdiffusion,OK?Soyougetapictureofapieceofbrain,andit'llshowyou,forexample,thatrightinthere,allthefibers--well,thewaterisdiffusingthisway.Andoverhere,thewater'sdiffusingthatway,OK?Andthat'sjustwhatyouseeinadiffusionimage,OK?

Andsotheinferencepeoplemakeisifyouhaveallthoseparallellinestellingyouthere'slotsofdiffusionlikethis,there'sprobablyabigfiberbundlegoinglikethat--andthereis.Thatwouldbethecorpuscallosum.OK?

Allright.Sothismethodworksgreatforfindingthebigfiberbundles.OK?I'mgoingtodisdiffusionimaginginabunchofways,butitisgreatforfindingthebigfiberbundlesbecauseinthosebigfiberbundles,axonsareveryparallel.There'sawholebunchofthem,andyoucanreallyseeit.OK.

Andsopeoplehavebeenusingthisforoveradecadetofindsomeofthemajorfiberbundlesinthebrain.SoyoumayhaveheardofthearcuatefasciculusthatbasicallyconnectslanguageregionsinthetemporallobeuptoBroca'sareainthefrontallobe,OK?It'sabigbunchoffibersthatgo--Iguessinme,theygolikethis,boom,right?[INAUDIBLE]And youcan seethoseguys with--thisisadistantreconstruction,butyoucanseethosewithdiffusionimaging.

Anotherone,thegoesfromthefrontofthetemporallobeuptothefrontallobe.Youdon'tneedtomemorizethese.Idon'tcareaboutthat.Ijustwantyoutogettheideaofwhatyoucansee.Yeah,question?

AUDIENCE:Sothesearediscoverablewithoutthepersonhavingtodoanything[INAUDIBLE]?

NANCY KANWISHER:Yes.Yes.Theseareanatomicalimages.Soindiffusionimaging,youdon'tdoanything.Youcansleep,actually.That'sidealbecauseit'slongandboring.

Actually,it'snotboring, butthescannershakeslikehellinadiffusion-imagingscan.It'sprettywild.Wecouldchargeadmissionforit.Idon'tknow.Ifinditquitewild.

Anyway,thisistheinferiorlongitudinalfasciculus.Asitgoesdownthetemporallobe.Sowhenwetalkabouttheventral-visualpathway--faceareas,placeareas,allthatstuff--thisisthebigfiberhighwaythatsitsrightontopofthatwholechunkofgraymatterthatdoesalltheprocessing.Andit'sabigpileoffibersthatgostraightdownthetemporallobe,OK?OK.

Andsohere'smorerecentdata.ThisisfromAnastasiaYendikioveratMHGCharlestownoverthere.Andshe'sdevelopedthislovelypieceofsoftwarethatenablesyoutotakediffusionimagesandidentify,basedonanatlasshe'sputtogether,18ofthemajorfibertractsinthehumanbrain--sonineperhemisphere.

Andthisisjustshowingyousomeofthebigones.ThisistheinferiorlongitudinalfasciculusIjustshowedyouandsoforth.Yeah.

AUDIENCE:Sohowdoesthiscomparetojustapostmortemdissection?Couldyouseethe--

NANCY KANWISHER:It'sagoodquestion.It'sagoodquestion.Idon'texactlyknow.Itwouldn'tbeeasy.ThatthingIshowedyouworksbecauseyoutakethestuffoffthetop,andit'sjustkindofsittingthere.Butthenyouwouldhavetakenalotofotherstuffout,andyouwouldn'tbeabletoseethatotherstuffyouhadtotakeout.YouknowwhatImean?

Sohere,youcansurfthroughandpickoutanyofthese.Soit'sdefinitelygoingtobebetter.ButwhichoftheseyoucanseewithpostmortemdissectionI'mnotsure--someofthem,someofthebiggeronesbutprobablynotallofthem.

OK,soherearesomeofthemajortracts.OK.Butyoucandoalittlebitmorethanjustfindthemwithdiffusionimaging.Youcanalsocharacterizethemalittlebit.Andthisisawholeuniverse.There'speoplewhospendtheirliveswithallkindsoffancymeasures,andI'mjustgoingtotellyouaboutthemostcommonone.

Sorecallthatthewholedealwithdiffusionimagingisit'slookingfororientationsofmaximumwaterdiffusion.Sosomepartsofthebrainhaveasystematicsetofdirectionsofwaterdiffusion,andotheronesdon't,right?Insideaventricle,thewatercangoanywhichway.There'snothingdeterminingwhichwayitgoes.

Sothisiscalledisotropicbecauseyouhavediffusiongoingequally--inequalamountsinalldirectionsandanisotropic,right?Soitgoessystematicallymoreinonedirection,oneaxisthanothers,OK?Diffusioncan'tseetheaxialdirection,likeleftorrightversustoleft.Itcanjustseethatthisaxisismoreprominentthanthisone,orthisone,orthisone,OK?Soyou'renotactuallyseeingitmoveinasystematicdirection.

OK,sothat'sthebasicsignal.Sowhatyoucandoisinalittlepatchofbrain,youcanasknotjust,whatdirectionhasmaximumdiffusion,whichiswhatI'vebeentalkingaboutsofar.Youcansay,howmuchmoredoesitgointhatmaximumdirectionthananyoftheothers?Isitmorelikethisormorelikethat?Andyoucanimagineawholespectrumin-between.

OK,soyou'rejustasking,howorientedisit?Isittotallyorientedorjustpartially?AndthatmeasureiscalledFractionalAnisotropy,orFA.It'sprominentenoughinthefieldyoushouldjustlearnthisphrase.Andyoureadanyarticles,especiallyanyclinicalarticles,thisisthefirstthingyou'llseeinanyclinicalpapersthatusediffusionimaging.

OK,andsofractionalanisotropy--there'sabunchoffancydefinitions.Andwedon'tcare.Wejustwanttheidea.It'sjust,towhatdegreeisthatlittlepatchofbraininthislittlepartofatractthatyou'veidentifiedmorelikethisormorelikethat,OK?Isitanisotropicorisotropic?OK?

Andsothishasbeenusedalottotrytoaskaboutthenatureoffibertractsindifferentgroups--youngversusold,differentclinicalgroups,autismversustypical,schizophrenia,younameit.Experience--youtrainpeopleuponatask--doyouchangetheFA,theFractionalAnisotropy,ofsomeparticulartract.OK?

Soit'sjustacharacteristicoftractis,howorientedisitalongtheway?Isitsuperclean,totallyoriented?Ordoesithavesomeisotropymixedin?OK?

Allright,sothisisallovertheliterature.LetmegiveyouonecoolexamplefromGabriellilabthatcameoutrecently.SotheyidentifiedthearcuatefasciculusthatIshowedyoubefore,goingfrom the--basically,Wernicke'sareacurvingarounduptoBroca'sareauptheresothatyoucanidentifyitanatomicallyineachsubjectindividually,OK?Nowyou'vegotit.You'veidentifiedwhichvoxelsarepartofthearcuatefasciculus.

Andthenwhattheywanttoask--whattheywantedtoaskis,istheintegrity,orthecharacteristicsofthearcuatefasciculus--isthatimportantforlanguage--fordyslexia?SotheymeasuredtheFAalongthistract.Howorientedisitallthewayalonghere?Andthenyougetsomekindofaverage.

Andtheymeasuredthatinabunchofkidswithdyslexiaandinabunchofkidswithnoreadingdisabilitywhoarematchedinotherdimensionsofnon-verbalcognitiveability,OK?Andwhattheyfoundisthefractionalanisotropywashigherinthetypicalkidsthanthekidswithreadingdisability,withdyslexia,OK?Andfromthat,theyimplicatedthatthisconnectionmayplaysomeroleindyslexia.OK?

It'snottotallyobviousbecauseonewouldthinkthisregionisconnectedtothatregion--thosearelanguageyregions,right?It'snotvisualregions.Youthinkofdyslexiaasaproblemseeingthelettersandwhichonesareorientedwhichway.Andthissuggeststhat,atleast,higher-levelconnectivitybetweenlanguageregionsmaybeimplicated,OK?Yeah.

AUDIENCE:Sothisjusttalksaboutthearchitectureandnottheperunitinformationbeing[INAUDIBLE]?

NANCY KANWISHER:That'sright.

AUDIENCE:There'snoinformation[INAUDIBLE].

NANCY KANWISHER:That'sright.It'sjustsaying,wherearethewires,andhoworganizedarethewires?Period.Yeah.

AUDIENCE:Sothey won'tflowthroughsometechniqueas--ifIcanmesswithit,likeI'mmeasuringit,ifthere'ssomemeanstomissthe[INAUDIBLE]diffusion,willthathaveanyeffect?

NANCY KANWISHER:Ididn'tquitegetthat.Sayitagain.

AUDIENCE:Sothere'sthiswaterdiffusionthat'shappeningthatI'mgoingtomeasure.ButwhatifIhavesomewaytointerveneandchangetherateofdiffusionsome such?

NANCY KANWISHER:Idon'tknowhowyou'ddothat.Imean,it'saprettybasicphysicalproperty--diffusionofwaterandhowit'sconstrainedbylipids,right?

AUDIENCE:Butthatshouldn'taffect,likethefunctionofinformationflow[INAUDIBLE]?

NANCY KANWISHER:Ooh.Ihavenoidea.Imean,that'sabiophysicalquestionIdon'tknowabout.Butnotice,thisisaprettydistantproxy.You'remostlylookingatwaterbetweenaxons,notevenwithinthem.Andsoit'sjustaproxyfor,howwellcanweseethosefibersandhowthey'reoriented,OK?

Yeah,it'sprettyremovedfromactualsignalsgoingalongthewires.Anyway,soeverybodygetthesensethat--you know,it'sonelittlefinding.Butitimplicatessomethingaboutthattractindyslexia.

OK,sothat'sinteresting.Butfirst,it'sjustcorrelational.Lotsofthingsarejustcorrelational.Mostofthestuffinthisclassisjustcorrelational.Sameistruehere.

Butalittlemoreseriously,it'snottotallyclearwhatfractionalanisotropymeans,OK?Sothere'sarealtraditionoftreatinghigh-fractionalanisotropyasifthat'sgood.Afterall,we'reinafiberbundle.Shouldn'talltheaxonsbeorientednicelyinthereandnotallscrambled?

Surely,orientedisgood,andscrambledisbad.Well,maybe,butsometimes,fiberscrossafiberbundle.Soyoucanhaveafiberbundlelikethiswithotherfiberscrossingit.

Andsowhenthathappens,maybethat'sgood.AndsopeopleuseFAasaproxyforgoodfiber.Peoplesay'fiberintegrity'even.Butthere'sawholequestionaboutwhatexactlyitmeans.Peoplewillspendtheirliveslookingatthebiophysicsoffibersandallthedifferentthingsthatfractionalanisotropyandtheothermeasuresmightmean.Andit'sactuallyprettycomplicatedandunresolved.

Anotherchallengewithfractionalanisotropyisit'sextremelyvulnerabletoartifacts.Allofdiffusionimagingisextremelyvulnerabletoartifacts,OK?AndI'mgoingtogiveyouanexampleofastudywedidafewyearsago.

SoIwas,forawhile,tryingtoworkonautism.I've,moreorless,givenupbecauseit's,asfarasIcantell,impossible.ButbackwhileIwasstilltrying,wescannedawholebunchofkidswithandwithoutautismwithdiffusionimaging,OK?

Andatthetime,therewereabout50publishedpapers,almostallofwhichsaidoneofthethingsyoufindwithautismisthatthere'sanunderdevelopmentoflong-rangeconnectivityandanoverdevelopmentofshort-rangeconnectivity.Andsothenpeoplewouldfreeassociatewithallkindsofspeculationsabout,OK,thisexplainsaspectsoftheautismphenotype.Theycan'tputdifferentideastogetherbecausetheirconnectionsacrossthebrainaren'tasgood.Andthey'reobsessedwithlittledetailsbecausetheyhavetoomanylocalconnectionsandallkindsof--suggestive,butvery,veryfuzzyideaslikethat.So50papersprettymuchallfoundunderdevelopedlowerfractionalanisotropyandlong-rangeconnections,long-rangetractsinautism,averyestablishedfinding

Sowewentinnottoraisehellbutjusttokindofreplicatesomeofthosebasicfindingswhilestudyingsomeotherthings.And,infact,whenwedidwhateveryoneelsedoes--thatisstandardanalysis--youcollectyourdiffusion-imagingdata,andyoueyeballitloosely,andifitreallylooksterriblytaintedwithartifact,youthrowthatsubjectout.And,otherwise,youkeepit,andyouanalyzeyourdata.Andyoulookat,herearethe18fibertractsthatIshowedyoubefore.Andyouask,whichofthosehavehigherorlowerfractionalanisotropyinkidswithautismcomparedtotypicalkids?

Andthebasicfinding--wereplicatedtheusualfinding.Andthatis,overall--thisiscolumnA--mostofthosetractsshowedlowerfractionalanisotropyinthekidswithautismthanthetypicalkids,OK?Manyofthosedifferenceswereindividuallysignificantinindividualtracts.Thosearetheoneswith theasterisks.

OK.Sothat'sthestandardfindingintheliterature,andwereplicatedit.However,wenoticedthatalotofthedatareallyseemedsuspect.Andwestartedmeasuringtheamountofheadmotionbetweenthekidswithautismandthekidswithout.Andguesswhat.Kidswithautismmoveinthescannermorethankidswithout.Andguesswhat.Diffusionimagingandfractionalanisotropyinparticulararehighlyinfluencedbyheadmotion.

Sothenwesaid,OK,let'sgetalittlemorecareful.Andsowedidamorestringentanalysis.Andwelookedatthekids.Wehadquiteafewofthemineachgroup.Andwetookthesubsetofkidswhowecouldmatchforheadmotion,OK?

Sonowwe'vegotthekidswithautismandthetypicalkids,butwe'venowgotthesubsetwehavetochoosetomatchforheadmotion,OK?Itusuallymeansthetypicalkidswhomovealittlemoreandtheautistickidswhohadslightlylessheadmotion.That'swhatyouneedtodotomatchthem.

Andwhenwedothat,theusualpatterndisappears.Nowthere'sonlyasingletractthatshowslowerfractionalanisotropyinthekidswithautismthanthetypicalkids,OK?Theinferiorlongitudinalfasciculus.Sothat'sworrying.

Butthenfurther,wethought,OKsincemanyofthosekidswehad,especiallythetypicalkids--manyofthemwehadscannedtwice.Sowethought,OK,let'sreallymakethiscase.Thisisclearlyaprobleminthefield.Infact,it'sabroaderproblem.Prettymuchanycomparisonacrossagegroupsorclinicalgroups--onegroupmovesmorethantheothergroup.Uh-oh.

Whatabouttheentireliterature?Hundreds,probablythousandsofpublishedpapers,essentially,noneofwhichpayattentiontothis--thisis2014.Peoplehavecleaneduptheiract since,butupuntil2014,almostnoneofthempaidanyattentiontothiswhoppingproblem.

Sowefiguredwebettermakethispointsalientbecausethere'salotofmoneyandtimebeingwastedpublishinggarbage.Andwewanttomakethepointsaliently.Sowetookthetypicalkidswhowehadscannedtwice,OK?Andsometimesakidwill--thesamekidwillmovemoreinonesessionthananothersession.

Sowesaid,OK,let'scomparetheverysamekidsonthesessionwheretheymovemorethanthesessionwheretheymovedless.Andyouknowwhat?Wereplicatedtheautismphenotype.Thoseweretypicalkids,notautistickids.

Thepointisheadmotionalonewillreducefractionalanisotropyandwilllookawholelotlikeaclinicaldisorder.Andsoeverytimeyouseethataclinicaldisorderismarkedbysomeanatomicaldifference,yourfirstthoughtshouldbe,howcarefullydidtheydealwithheadmotionandotherartifactsthataregoingtodifferbetweengroups?OK?

SoIsaythatnotto distheentireliteraturebutjusttoalertyouthatthesethingscanreallymatter.ThepaperfromGabrielliLabthatIjustdescribed--Ilooked,ofcourse,beforeIpresenteditinhere,andtheycitedus,andtheyusedourmethodsformatchingheadmotion--goodforthem.Sothesethingsarechanging,andIthinkthefieldwillstartcleaningupitsact.Butit'samazingittookthislong.

OK.Allright,sofindingfibertractsandcharacterizingthemwithfractionalanisotropyarenice,but,really,whatwewanttoknowiswhat'sconnectedtowhat,OK?Whichofthesethingsareconnectedtoeachother?Whichotherbrainregionsaretheyconnectedto?

Andsotofindthatout,weneedtonotjuststudywhitematteritselfandthetracts,butwehavetogetoutofthetractsandintothegraymatter.Soweneedtostartinapatchofgraymatterandfigureoutwherewecangobyfollowingthoseaxons,OK?Andsothemethodfordoingthatiscalledtractography.Sotherearemanyversionsofthis.Ishowedbrieflythesepicturesbefore.I'msureyou'veseenthese.

Thesimplestideaofwhatyoudo,leavingoutallthedetails,isyoustartinsomegray-matterregion,somevoxelinthegraymatter.Youwanttoknowwhatit'sconnectedto.Youjustfollowthoselittleorientations,andyou can--youseewhereyoucango.OK?

Andsothat'sbasicallyhowyoumakethisdiagram.OK?You'rejustfollowingthose.Youstartoverhereyoufollowtheorientation--godo,do, do,do, do,do, do,right?OK?Imean,youdothatinacomputer,right?Analgorithmdoesthat,followsalong--ch, ch,OK?

OK,sothat'scalledtractography.Andtheidea'sawesome--howgreattobeabletoseewhat'sconnectedtowhat.Andtherearemany,manythousandsofpapersthatdothisforgoodreason.Weneedtoknowwhat'sconnectedtowhat.

Thisisourcurrentlybestmethodforlookingatthestructuralconnectivityofdifferentgray-matterregionstoeachother.Andsoyoucanask,forexample,OK,let'sputaseedinthefusiformfaceareaandseewhereitgoes.Wouldn'tthatbecool?Right.Wouldn'titbecool?

Unfortunately,itdoesn'twork.SoIhavetotellyouthatIdon'tknowifI'mthebestpersontoreporttothisbecauseI'mnot--I'veonlybeentryingtodothisforafewyears.But,I'vebeencollaboratingwiththebestpeopleintheworldoverthereatMGHCharlestownwhoareworkingcloselywithus.Andwecan'tgetthisthingtoworkworthadamn.

AndsonowI'mactuallyconfusedwhethertheentireliteratureisgarbage.Idon'tthinkit'sentirelygarbage.ButIthinkit'sfullofoveroptimisticevaluationsofwhatyoucantellfromtractographybecauseinourhands,westartedwithrealitychecks,putaseedinthelateralgeniculatenucleus.Let'smakedamnsurewecangetuptoV1.Well,youcangetuptoV1,butyoucangetuptoV2,andV3,andV4,aswell,whichareallwrong,right?LGNonlygoestoV1.

Worse,youstickaseednextdoorinthemedialgeniculatenucleus,whichisthepartofthethalamusthatgoesuptoauditorycortex,youalsoendupinV1.Wrong.Wrong.Wrong.Wrong.There'snotverymanyanatomicalconnectionsinthehumanbrainwhereweactuallyknowtherightanswerwherewecandotheserealitychecks,butoftheonesweknowthatwe'vetried,itdoesn'twork.

Andwe'reusingthebestdiffusion-imagingscannerintheworld.It'srightoverthere.SomaybeI'mdoingeverythingwrong.Butattheveryleast,Ithinktherearealotofproblemswiththismethod.

Thisisnotjustmeworryingaboutthis.Andmanypeoplehavebeenworryingaboutthisforthewhole15,20-yearlifeofdiffusiontractography.Andsomeofthechallengesare,like,famous.

Sotofollowthoselittleorientations,youneed to--youcansee,likethere'dbelotsofplaceswhere,OK,there'sabunchofdifferentwaysyoucouldgo.It'sillposed,right?Sopeopleuseheuristicstoconstrainthosesolutions.Andthoseheuristicsarebasedonassumptionsabouthowfibersbendinthebrain,namelythattheydon'tmakereallysharpangles,right?That'sreasonable.Mostofthetimetheydon't,butsometimestheydo.

Andinparticular,whenyou'regoingfromwhitemattertocortex,often,youmakeaverysharpturn.Andsoit'svery,verydifficulttofigureouthowtogetfromagivengray-matterpatchintotheunderlyingwhitematterexactlywhattheconnectivityis.Sothat'soneproblem.

Anotherfamousproblemwithtractographyiscalledthecrossing-fiberproblem.Soimagineabunchofaxonssomewhereinthebrainthatcrosslikethisversusimagineabunchoffibersinthebrainthatcomeuptoeachotherandthengoapart,OK?Everybodygetthis?Theconnectivity'stotallydifferenthere--nowayyou'reevergoingtodistinguishthosewithdiffusiontractography.Sopeopletrytogethigherandhigherresolutiontoseedownthoseindividualthings,butthey'renotthere.Yeah.

AUDIENCE:Whywouldsomethinglikethathappen?

NANCY KANWISHER:Yeah,whywouldtheydothat?Weirdstuffhappensinthebrain.Soit'snotincrediblycommon,butit'snotunheardof.

Yeah,remember,thebrainwasn'tdissolved--designednowoptimallytosolvealltheproblemsitneedstosolvewiththeoptimalsolutionfromscratch.Itevolvedgraduallyovertime.Andsothereareallkindsofweirdthingsthatareworkaroundsforpre-existingdecisionsthatevolutionmadeearlier.Andsobothbrainandbodyhavelotsofbizarreattributesthataren'thowyouwoulddesignitfromscratch.They'rejustthefixthatevolutionmadeatthatpointgivenwhathadalreadybeenfixed.Andsothere'sweirdstufflikethat.

Anyway,ImentionthistosayI'mmorenegativeaboutdiffusiontractographythanprobablyanyoneelsebecauseI'vespentalotofthelasttwoyearstryingtodoit,andit'sbigbust,andI'mcranky.Soit'sprobablynotasbadasI'mlayingout.Plentyofpeopledoit.Theygetsomekindofanswersoutofit,butit'sproblematicatleast.