Critical period - Wikipedia

文章推薦指數: 80 %
投票人數:10人

In developmental psychology and developmental biology, a critical period is a maturational stage in the lifespan of an organism during which the nervous ... Criticalperiod FromWikipedia,thefreeencyclopedia Jumptonavigation Jumptosearch Maturationalstageinthelifespanofanorganism Forotheruses,seewindowofopportunity. Indevelopmentalpsychologyanddevelopmentalbiology,acriticalperiodisamaturationalstageinthelifespanofanorganismduringwhichthenervoussystemisespeciallysensitivetocertainenvironmentalstimuli.If,forsomereason,theorganismdoesnotreceivetheappropriatestimulusduringthis"criticalperiod"tolearnagivenskillortrait,itmaybedifficult,ultimatelylesssuccessful,orevenimpossible,todevelopcertainassociatedfunctionslaterinlife.Functionsthatareindispensabletoanorganism'ssurvival,suchasvision,areparticularlylikelytodevelopduringcriticalperiods."Criticalperiod"alsorelatestotheabilitytoacquireone'sfirstlanguage.Researchersfoundthatpeoplewhopassedthe"criticalperiod"wouldnotacquiretheirfirstlanguagefluently.[1] Someresearchersdifferentiatebetween'strongcriticalperiods'and'weakcriticalperiods'(a.k.a.'sensitive'periods)—defining'weakcriticalperiods'/'sensitiveperiods'asmoreextendedperiods,afterwhichlearningisstillpossible.[2]Otherresearchersconsiderthesethesamephenomenon.[3] Forexample,thecriticalperiodforthedevelopmentofahumanchild'sbinocularvisionisthoughttobebetweenthreeandeightmonths,withsensitivitytodamageextendinguptoatleastthreeyearsofage.Furthercriticalperiodshavebeenidentifiedforthedevelopmentofhearing[4]andthevestibularsystem.[1] Contents 1Strongversusweakcriticalperiods 2Criticalperiodmechanisms 2.1Criticalperiodopening 2.2Activity-dependentcompetition 2.2.1Oculardominance 2.2.2Axongrowth 2.3Microglia 2.4Spinemotility 2.5Excitatory-inhibitorybalance 2.6Criticalperiodclosure 2.6.1Perineuronalnets 2.6.2Myelin 2.7Neuromodulation 3Linguistics 3.1Firstlanguageacquisition 3.2Secondlanguageacquisition 4Vision 5Imprinting 6Auditoryprocessing 6.1Musicalability 7Vestibularsystem 8Memory 9Seealso 10References 11Externallinks Strongversusweakcriticalperiods[edit] Examplesofstrongcriticalperiodsincludemonoculardeprivation,filialimprinting,monauralocclusion,[5]andPrefrontalSynthesisacquisition.[6]Thesetraitscannotbeacquiredaftertheendofthecriticalperiod. Examplesofweakcriticalperiodsincludephonemetuning,grammarprocessing,articulationcontrol,vocabularyacquisition,musictraining,auditoryprocessing,sporttraining,andmanyothertraitsthatcanbesignificantlyimprovedbytrainingatanyage.[7][8] Criticalperiodmechanisms[edit] Criticalperiodopening[edit] Criticalperiodsofplasticityoccurintheprenatalbrainandcontinuethroughoutchildhooduntiladolescenceandareverylimitedduringadulthood.Twomajorfactorsinfluencetheopeningofcriticalperiods:cellularevents(i.e.changesinmolecularlandscape)andsensoryexperience(i.e.hearingsound,visualinput,etc).Bothneedtocoincideforthecriticalperiodtoopenproperly.Atthecellularlevel,criticalperiodsarecharacterizedbymaturationoftheinhibitorycircuits.[9]Moreprecisely,factorssuchasbrain-derivedneurotrophicfactor(BDNF)andorthodenticlehomeobox2(Otx2)contributetothematurationofamajorclassofinhibitoryneurons:parvalbumin-positiveinterneurons(PVcells).[9]Priortotheonsetofthecriticalperiod,modulationofthiscircuitishamperedbyearlyfactorssuchaspolysialicacid(PSA).[9]PSAacts,inpart,bypreventingOtx2interactionwithPVcells.[10]Soonaftertheopeningofthecriticalperiod,PSAlevelsdecrease,allowingPVcellmaturationbyactivatinginhibitoryGABAareceptorsthatfacilitateinhibitorycircuitremodeling.ArtificiallyremovingPSA,orexperimentallymanipulatinginhibitorytransmissioncanresultinearlyopeningofthecriticalperiod.[10][11]Whilethetimingofthesemoleculareventsseemstobepartiallyexplainedbyclockgenes,[12]experienceiscrucialassensorydeprivationexperimentshavebeenshowntointerferewiththepropertimingofcriticalperiods.[13][14][15] Activity-dependentcompetition[edit] Hebbiantheoryguidestheideaofactivity-dependentcompetition:iftwoneuronsbothhavethepotentialtomakeaconnectionwithacell,theneuronthatfiresmorewillmaketheconnection. Oculardominance[edit] Thisphenomenonofactivity-dependentcompetitionisespeciallyseenintheformationofoculardominancecolumnswithinthevisualsystem.Earlyindevelopment,mostofthevisualcortexisbinocular,meaningitreceivesroughlyequalinputfrombotheyes.[16]Normally,asdevelopmentprogresses,thevisualcortexwillsegregateintomonocularcolumnsthatreceiveinputfromonlyoneeye.[16]However,ifoneeyeispatched,orotherwisepreventedfromreceivingsensoryinput,thevisualcortexwillshifttofavorrepresentationoftheuncoveredeye.Thisdemonstratesactivity-dependentcompetitionandHebbiantheorybecauseinputsfromtheuncoveredeyemakeandretainmoreconnectionsthanthepatchedeye.[17] Axongrowth[edit] Furtherinformation:Axonguidance Axonformationandgrowthisanotherkeypartofplasticityandactivity-dependentcompetition.Axongrowthandbranchinghasbeenshowntobeinhibitedwhentheneuron'selectricalactivityissuppressedbelowthelevelofanactiveneighbor.[18]Thisshowsthataxonalgrowthdynamicsarenotindependentbutratherdependonthelocalcircuitswithinwhichtheyareactive(i.e.theactivityoftheotherneuronscompetingforconnections). Microglia[edit] Microgliainherentlyplayaroleinsynapticpruningduringadolescence.Asresidentimmunecellsofthecentralnervoussystem,microglia’smainroleisphagocytosisandengulfment.Studieshavefoundthatduringcriticalperiodsinthevisualcortex,neuralsynapsesbecomethetargetofmicroglialphagocytosis.[19][20]Neuronswhoreceivedlessfrequentinputfromretinalganglioncellsduringearlypostnatalperiodsweremorepronetobeengulfedandprunedbymicroglia,aspermonoculardeprivationexperiments.[19]SimilarresultswerefoundwhenmanipulatingG-coupledpurinergicreceptorsonmicroglialprocesses.Blockingthesereceptorsorperformingaknockoutexperimentsignificantlyloweredmicroglialinteractionsandsynapticpruningduringtheearlyvisualcortexcriticalperiod.[20]Morerecently,theexpressionofthecomplementcomponent4genehasbeenfoundtosignificantlycontributetoabnormallyhighlevelsofmicroglialsynapticpruningduringearlystagesofdevelopmentinschizophrenicneuronsandmicroglia,suggestingagenomicconnectionbetweentheimmunesystemandcriticalperiods.[21] Spinemotility[edit] Dendriticspinemotilityisthealteringofthedendriticmorphologyofaneuron,specificallytheappearinganddisappearingofthesmallprotrusionsknownasspines.Inearlypostnataldevelopment,spinemotilityhasbeenfoundtobeatveryhighlevels.Duetoitsmostpronouncedoccurrenceduringpostnataldays11through15,spinemotilityisthoughttohavearoleinneurogenesis.[22]Motilitylevelssignificantlydecreasebeforethestartofthevisualcortexcriticalperiodandmonoculardeprivationexperimentsshowthatmotilitylevelssteadilydecreaseuntilthecriticalperiodisover,hintingthatmotilitymightnotbeexplicitlyinvolvedinthisprocess.[23]However,binoculardeprivationbeforeeye-openingresultedinasignificantup-regulationofspinemotilityuntilthepeakofthecriticalperiod,[24]resultingincontroversialfindingsregardingtheroleofdendriticspinemotility. Excitatory-inhibitorybalance[edit] Anothercriticalcomponentofneuronalplasticityisthebalanceofexcitatoryandinhibitoryinputs.Earlyindevelopment,GABA,themajorinhibitoryneurotransmitterintheadultbrain,exhibitsanexcitatoryeffectonitstargetneurons.[25]However,duetochangesininternalchloridelevelsduetotheup-regulationofpotassiumchloridepumps,GABAthenswitchestoinhibitorysynaptictransmission.[25]ThematurationoftheGABAergicinhibitorysystemhelpstotriggertheonsetofcriticalperiods.[11]StrengthenedGABAergicsystemscaninduceanearlycriticalperiod,whileweakerGABAergicinputscandelayorevenpreventplasticity.[26][27]Inhibitionalsoguidesplasticityoncethecriticalperiodhasbegun.Forexample,lateralinhibitionisespeciallyimportantinguidingcolumnarformationinthevisualcortex.[28]Hebbiantheoryprovidesinsightontheimportanceofinhibitionwithinneuralnetworks:withoutinhibition,therewouldbemoresynchronousfiringandthereforemoreconnections,butwithinhibition,fewerexcitatorysignalsgetthrough,allowingonlythemoresalientconnectionstomature.[29] Criticalperiodclosure[edit] Perineuronalnets[edit] Criticalperiodclosurehasbeenshowntobemodulatedbythematurationofinhibitorycircuits,mediatedbytheformationofperineuronalnetsaroundinhibitoryneurons.[11]Perineuronalnets(PNNs)arestructuresintheextracellularmatrixformedbychondroitinsulfateproteoglycans,hyaluronan,andlinkproteins.[30]Thesestructuresenvelopthesomaofinhibitoryneuronsinthecentralnervoussystem,appearingwithagetostabilizematurecircuits.[30][31]PNNdevelopmentcoincideswiththeclosureofcriticalperiods,andbothPNNformationandcriticalperiodtimingisdelayedindark-rearing.[31]Forexample,PNNdigestionbyABCchondroitinaseinratsleadstoashiftinoculardominanceuponmonoculardeprivation,whichisnormallyrestrictedtoitscriticalperiodmuchearlierindevelopment.[32] Additionally,PNNsarenegativelycharged,whichistheorizedtocreateacation-richenvironmentaroundcells,potentiallyleadingtoanincreasedfiringrateofinhibitoryneurons,therebyallowingforincreasedinhibitionaftertheformationofPNNsandhelpingtoclosethecriticalperiod.[33]TheroleofPNNsincriticalperiodclosureisfurthersupportedbythefindingthatfast-spikingparvalbulmin-positiveinterneuronsareoftensurroundedbyPNNs.[33] Perineuronalnetshavealsobeenfoundtocontainchemorepulsivefactors,suchassemaphorin3A,whichrestrictaxongrowthnecessaryforplasticityduringcriticalperiods.[34]Inall,thesedatasuggestaroleforPNNsinthematurationofCNSinhibition,thepreventionofplasticaxonalgrowth,andsubsequently,criticalperiodclosure. Myelin[edit] Anothermechanismthatclosesthecriticalperiodismyelination.MyelinsheathsareformedbyoligodendrocytesintheCNSthatwraparoundsegmentsofaxonstoincreasetheirfiringspeed.[35]Myelinisformedintheearlystagesofdevelopmentandprogressesinwaves,withbrainareasoflaterphylogeneticdevelopment(i.e.thoseassociatedwith“higher”brainfunctionslikethefrontallobes)havinglatermyelination.[36]Thematurationofmyelinationinintracorticallayerscoincideswithcriticalperiodclosureinmice,whichhasledtofurtherresearchontheroleofmyelinationoncriticalperiodduration.[37] Myelinisknowntobindmanydifferentaxonalgrowthinhibitorsthatpreventplasticityseenincriticalperiods.[38]TheNogoReceptorisexpressedinmyelinandbindstotheaxonalgrowthinhibitorsNogoandMAG(amongothers),preventingaxongrowthinmature,myelinatedneurons.[38]Insteadofaffectingthetimingofthecriticalperiod,mutationsoftheNogoreceptorprolongthecriticalperiodtemporarily.[37]AmutationoftheNogoreceptorinmicewasfoundtoextendthecriticalperiodformonoculardominancefromaround20–32daysto45or120days,suggestingalikelyroleofthemyelinNogoreceptorincriticalperiodclosure.[37] Additionally,theeffectsofmyelinationaretemporallylimited,sincemyelinationitselfmayhaveitsowncriticalperiodandtiming.[36][39]Researchhasshownthatsocialisolationofmiceleadstoreducedmyelinthicknessandpoorworkingmemory,butonlyduringajuvenilecriticalperiod.[39]Inprimates,isolationiscorrelatedwithabnormalchangesinwhitematterpotentiallyduetodecreasedmyelination.[40] Inall,myelinanditsassociatedreceptorsbindseveralimportantaxonalgrowthinhibitorswhichhelpclosethecriticalperiod.[37][38]Thetimingofthismyelination,however,isdependentonthebrainregionandexternalfactorssuchasthesocialenvironment.[36][39] Neuromodulation[edit] Whilethepresenceorabsenceofsensoryexperiencesmostrobustlyshapesbraindevelopmentduringthecriticalperiod,thebehavioralcontext(i.e.theamountofattention,arousal,fearandrewardexperienced)concurrentwiththesensoryinputshavebeensuggestedtobeimportantinregulatingthebrainremodelingmechanisms.[41][42][43][44][45]Intermsofbrainconnectivity,thesebehavioralandcontextualinputsactivatetheneuromodulatorysystem,whichhavesubstantialconnectivitytothecortex[43][44][46][47]Themoleculareffectorsreleasedbytheneuromodulatorysystemarecalledneuromodulators,whichincludeacetylcholine,dopamine,andnoradrenalineamongothers.[46]Investigatingtheeffectofthesemolecules,aswellastheneuronsthatreleaseandbindthem,hasbeenoneapproachtoelucidatethebiologyofneuromodulation.Researchusingthisapproachhashighlightedtheroleofneuromodulationinsensoryprocessingduringthecriticalperiod.[11][43][44][45][47][48][49]Forexample,ontheonehand,inkittens,ashiftinoculardominanceresultingfrommonoculardeprivationduringthecriticalperiodisreducedbycombineddestructionofnoradrenergicandcholinergicneurons.[48]Inaddition,prenatalexposuretoselectiveserotoninreuptakeinhibitors(SSRI)causesashiftinperceptualnarrowingonlanguagetoearlierindevelopment.[50]Ontheotherhand,neuromodulatorystimulationhasbeenshowntoinducebrainplasticityinadultmice.[43][44]Whilebeingsubjectedtocholinergicordopaminergicstimulation,adultmicelisteningtoatoneofspecificfrequencyexhibitedexpansionofthetonotopicareaintheauditorycortexthatrespondsspecificallytosoundsofthatfrequency.[43][44] Mechanistically,neuromodulationisincreasinglybeingrecognizedforitsfine-tuningofthePVcell-mediatedinhibitionofexcitatorypyramidalneurons'soma.[45][49][51]CentraltotheneuromodulatoryregulationofPVcellactivityistheexistenceofdistinctsubsetsofinhibitoryneurons,whichareresponsivetoactivationbyneuromodulatorsandwhichinhibitPVcells.[9][45][49][51]Withinthesecells,somealsoinhibitspecificpyramidalcelldendrites.[45][49]ByinhibitingPVcellsactivity,theneuromodulator-sensitiveinhibitorycellssuchasthoseexpressingVasoactiveintestinalpeptide(VIP)orsomatostatin(SST)lifttheinhibitionofthepyramidalneurons;inotherwords,theactivityofVIPandSST-expressingcellsresultinthedisinhibitionofpyramidalneurons.[9][45][49][51]Then,byinhibitingonlycertaindendriticbranchesofthesenowdis-inhibitedpyramidalneurons,theneuromodulation-activatedcellsallowselectsensoryinputstoexcitethepyramidalneuronsandberepresentedinthebraincircuitry.[45][49]Thus,inalandscapeofglobalinhibitionbymaturinginhibitorysignaling,neuromodulationallowswindowsofdis-inhibition,temporallyandspatially,thatallowbehaviorallyimportantsensoryinputstheopportunitytoinfluencethebrain.[45][49] Linguistics[edit] Mainarticle:Criticalperiodhypothesis Firstlanguageacquisition[edit] Thecriticalperiodhypothesis(CPH)statesthatthefirstfewyearsoflifeconstitutethetimeduringwhichlanguagedevelopsreadilyandafterwhich(sometimebetweenage5andpuberty)languageacquisitionismuchmoredifficultandultimatelylesssuccessful.[52]ThehypothesisthatlanguageisacquiredduringacriticalperiodwasfirstproposedbyneurologistsWilderPenfieldandLamarRobertsin1959andpopularizedbylinguistEricLennebergin1967.Lennebergarguedforthehypothesisbasedonevidencethatchildrenwhoexperiencebraininjuryearlyinlifedevelopfarbetterlanguageskillsthanadultswithsimilarinjuries. Dr.MariaMontessoriwasoneoftheearliereducatorswhobroughtattentiontothisphenomenonandcalledit"SensitivePeriods",whichisoneofthepillarsofherphilosophyofeducation. ThetwomostfamouscasesofchildrenwhofailedtoacquirelanguageafterthecriticalperiodareGenieandtheferalchildVictorofAveyron.[53]However,thetragiccircumstancesofthesecasesandthemoralandethicalimpermissibilityofreplicatingthemmakeitdifficulttodrawconclusionsaboutthem.Thechildrenmayhavebeencognitivelydisabledfrominfancy,ortheirinabilitytodeveloplanguagemayhaveresultedfromtheprofoundneglectandabusetheysuffered.[52] ManysubsequentresearchershavefurtherdevelopedtheCPH,mostnotablyElissaNewportandRachelMayberry.Studiesconductedbytheseresearchersdemonstratedthatprofoundlydeafindividualswhoarenotexposedtoasignlanguageaschildrenneverachievefullproficiency,evenafter30yearsofdailyuse.[54]Whiletheeffectismostprofoundforindividualswhoreceivenosignlanguageinputuntilaftertheageof12,eventhosedeafpeoplewhobeganlearningasignlanguageatage5weresignificantlylessfluentthannativedeafsigners(whoseexposuretoasignlanguagebeganatbirth).Earlylanguageexposurealsoaffectstheabilitytolearnasecondlanguagelaterinlife:profoundlydeafindividualswithearlylanguageexposureachievecomparablelevelsofproficiencyinasecondlanguagetohearingindividualswithearlylanguageexposure.Incontrast,deafindividualswithoutearlylanguageexposureperformfarworse.[55] Otherevidencecomesfromneuropsychologywhereitisknownthatadultswellbeyondthecriticalperiodaremorelikelytosufferpermanentlanguageimpairmentfrombraindamagethanarechildren,believedtobeduetoyouthfulresiliencyofneuralreorganization.[52] StevenPinkerdiscussestheCPHinhisbook,TheLanguageInstinct.AccordingtoPinker,languagemustbeviewedasaconceptratherthanaspecificlanguagebecausethesounds,grammar,meaning,vocabulary,andsocialnormsplayanimportantroleintheacquisitionoflanguage.[56]Physiologicalchangesinthebrainarealsoconceivablecausesfortheterminusofthecriticalperiodforlanguageacquisition.[57]Aslanguageacquisitioniscrucialduringthisphase,similarlyinfant-parentattachmentiscrucialforsocialdevelopmentoftheinfant.Aninfantlearnstotrustandfeelsafewiththeparent,buttherearecasesinwhichtheinfantmightbestayingatanorphanagewhereitdoesnotreceivethesameattachmentwiththeircaregiver.Researchshowsthatinfantswhowereunabletodevelopthisattachmenthadmajordifficultyinkeepingcloserelationships,andhadmaladaptivebehaviorswithadoptedparents.[1] Thediscussionoflanguagecriticalperiodsuffersfromthelackofacommonlyaccepteddefinitionoflanguage.Someaspectsoflanguage,suchasphonemetuning,grammarprocessing,articulationcontrol,andvocabularyacquisitioncanbesignificantlyimprovedbytrainingatanyageandthereforehaveweakcriticalperiods.[7][8]Otheraspectsoflanguage,suchasPrefrontalSynthesis,havestrongcriticalperiodsandcannotbeacquiredaftertheendofthecriticalperiod.[6]Consequently,whenlanguageisdiscussedingeneral,withoutdissectionintocomponents,argumentscanbeconstructedbothinfavorandagainstthestrongcriticalperiodofL1acquisition. Secondlanguageacquisition[edit] Thetheory[58]hasoftenbeenextendedtoacriticalperiodforsecondlanguageacquisition(SLA),whichhasinfluencedresearchersinthefieldonbothsidesofthespectrum,supportiveandunsupportiveofCPH,toexplore.[59]However,thenatureofthisphenomenonhasbeenoneofthemostfiercelydebatedissuesinpsycholinguisticsandcognitivescienceingeneralfordecades. Certainly,olderlearnersofasecondlanguagerarelyachievethenative-likefluencythatyoungerlearnersdisplay,despiteoftenprogressingfasterthanchildrenintheinitialstages.ThisisgenerallyacceptedasevidencesupportingtheCPH.Incorporatingtheidea,"youngerequalsbetter"byPenfield,DavidSingleton(1995)statesthatinlearningasecondlanguagetherearemanyexceptions,notingthatfivepercentofadultbilingualsmasterasecondlanguageeventhoughtheybeginlearningitwhentheyarewellintoadulthood—longafteranycriticalperiodhaspresumablycometoaclose.Thecriticalperiodhypothesisholdsthatfirstlanguageacquisitionmustoccurbeforecerebrallateralizationcompletes,atabouttheageofpuberty.Onepredictionofthishypothesisisthatsecondlanguageacquisitionisrelativelyfast,successful,andqualitativelysimilartofirstlanguageonlyifitoccursbeforetheageofpuberty.[60]TograspabetterunderstandingofSLA,itisessentialtoconsiderlinguistic,cognitive,andsocialfactorsratherthanagealone,astheyareallessentialtothelearner'slanguageacquisition.[59] Overtheyears,manyexperimentershavetriedtofindevidenceinsupportoforagainstthecriticalperiodsfor secondlanguageacquisition. Manyhavefoundevidencethatyoungchildrenacquire language moreeasilythanadults,buttherearealsospecialcasesofadultsacquiringasecondlanguagewithnative-likeproficiency.Thusithasbeendifficultforresearcherstoseparate correlation from causation.[61] In1989,JacquelineS.JohnsonandElissaL.Newportfoundsupportfortheclaimthatsecondlanguagesaremoreeasilyacquiredbefore puberty,ormorespecificallybeforetheageofseven.[62]Theytestedsecondlanguagelearnersof English whoarrivedintheUnitedStatesatvariousagesrangingfromthreetothirty-nine,andfoundthattherewasadeclineingrammaticalcorrectnessaftertheageofseven.JohnsonandNewportattributedthisclaimtoadeclineinlanguagelearningabilitywithage.OpponentsofthecriticalperiodarguethatthedifferenceinlanguageabilityfoundbyJohnsonandNewportcouldbeduetothedifferenttypesofinputthatchildrenandadultsreceive;childrenreceivedreducedinputwhileadultsreceivemorecomplicatedstructures. Additionalevidenceagainstastrict criticalperiod isalsofoundintheworkofPallieretal.(2003)whofoundthatchildrenadoptedto France from Korea wereabletobecomenative-likeintheirperformanceof French evenafterthecriticalperiodfor phonology.[63]Theirexperimentmayrepresentaspecialcasewheresubjectsmustlosetheirfirstlanguageinordertomoreperfectlyacquiretheirsecond. Thereisalsosomedebateastohowonecanjudgethenative-likequalityofthespeechparticipantsproduceandwhatexactlyitmeanstobeanear-nativespeakerofasecondlanguage.[64]Whiteetal.foundthatitispossiblefornon-nativespeakersofalanguagetobecomenative-likeinsomeaspects,butthoseaspectsareinfluencedbytheir firstlanguage. Recently,aconnectionistmodelhasbeendevelopedtoexplainthechangesthattakeplaceinsecondlanguagelearningassumingthatsensitiveperiodaffectslexicallearningandsyntacticlearningpartsofthesystemdifferently,whichshedsfurtherlightonhowfirstandsecondlanguageacquisitionchangesoverthecourseoflearnersdevelopment.[65] Vision[edit] Inmammals,neuronsinthebrainthatprocessvisionactuallydevelopafterbirthbasedonsignalsfromtheeyes.AlandmarkexperimentbyDavidH.HubelandTorstenWiesel(1963)showedthatcatsthathadoneeyesewnshutfrombirthtothreemonthsofage(monoculardeprivation)onlyfullydevelopedvisionintheopeneye.Theyshowedthatcolumnsintheprimaryvisualcortexreceivinginputsfromtheothereyetookovertheareasthatwouldnormallyreceiveinputfromthedeprivedeye.Ingeneralelectrophysiologicalanalysesofaxonsandneuronsinthelateralgeniculatenucleusshowedthatthevisualreceptivefieldpropertieswascomparabletoadultcats.However,thelayersofcortexthatweredeprivedhadlessactivityandfewerresponseswereisolated.Thekittenshadabnormallysmalloculardominancecolumns(partofthebrainthatprocessessight)connectedtotheclosedeye,andabnormallylarge,widecolumnsconnectedtotheopeneye.Becausethecriticalperiodtimehadelapsed,itwouldbeimpossibleforthekittenstoalteranddevelopvisionintheclosedeye.Thisdidnothappentoadultcatsevenwhenoneeyewassewnshutforayearbecausetheyhadfullydevelopedtheirvisionduringtheircriticalperiod.Laterexperimentsinmonkeysfoundsimilarresultsconsistentwiththestrongcriticalperiod.[66] Inafollow-upexperiment,HubelandWiesel(1963)exploredthecorticalresponsespresentinkittensafterbinoculardeprivation;theyfounditdifficulttofindanyactivecellsinthecortex,andtheresponsestheydidgetwereeitherslow-movingorfast-fatiguing.Furthermore,thecellsthatdidrespondselectedforedgesandbarswithdistinctorientationpreferences.Nevertheless,thesekittensdevelopednormalbinocularity.HubelandWieselfirstexplainedthemechanism,knownasorientationselectivity,inthemammalianvisualcortex.Orientationtuning,amodelthatoriginatedwiththeirmodel,isaconceptinwhichreceptivefieldsofneuronsintheLGNexciteacorticalsimplecellandarearrangedinrows.Thismodelwasimportantbecauseitwasabletodescribeastrongcriticalperiodfortheproperdevelopmentofnormaloculardominancecolumnsinthelateralgeniculatenucleus,andthusabletoexplaintheeffectsofmonoculardeprivationduringthiscriticalperiod.Thecriticalperiodforcatsisaboutthreemonthsandformonkeys,aboutsixmonths.[67] Inasimilarexperiment,AntoniniandStryker(1993)examinedtheanatomicalchangesthatcanbeobservedaftermonoculardeprivation.Theycomparedgeniculocorticalaxonalarborsinmonocularlydeprivedanimalsinthelongterm(4-weeks)toshortterm(6–7days)duringthecriticalperiodestablishedbyHubelandWiesel(1993).Theyfoundthatinthelongterm,monoculardeprivationcausesreducedbranchingattheendofneurons,whiletheamountofafferentsallocatedtothenondeprivedeyeincreased.Evenintheshortterm,AntoniniandStryker(1993)foundthatgeniculocorticalneuronsweresimilarlyaffected.Thissupportstheaforementionedconceptofacriticalperiodforproperneuraldevelopmentforvisioninthecortex.[68] Studiesofpeoplewhosesighthasbeenrestoredafteralongblindness(whetherfrombirthoralaterpointinlife)revealthattheycannotnecessarilyrecognizeobjectsandfaces(asopposedtocolor,motion,andsimplegeometricshapes).Somehypothesizethatbeingblindduringchildhoodpreventssomepartofthevisualsystemnecessaryforthesehigher-leveltasksfromdevelopingproperly.[69]Thegeneralbeliefthatacriticalperiodlastsuntilage5or6waschallengedbya2007studythatfoundthatolderpatientscouldimprovetheseabilitieswithyearsofexposure.[70] ExpressionoftheproteinLynx1hasbeenassociatedwiththenormalendofthecriticalperiodforsynapticplasticityinthevisualsystem.[71] Imprinting[edit] KonradLorenz Inpsychology,imprintingisanytypeofrapidlearningthatoccursinaparticularlifestage.Whilethisrapidlearningisindependentofthebehavioraloutcome,italsoestablishesitandcanaffectbehavioralresponsestodifferentstimuli.KonradLorenziswellknownforhisclassicstudiesoffilialimprintingingraylaggeese.From1935to1938,hepresentedhimselftoagroupofnewlyhatchedgoslingandtooknoteofhowhewasinstantlyaccepted,followed,andcalledtoasifheweretheonewholaidthemhimself.Asthefirstmovingobjecttheyencountered,Lorenzstudiedthephenomenoninhowquicklythegeesewereabletoformsuchanirreversiblebond.Throughhisworkhedemonstratedthatthisonlydevelopedduringabrief“criticalperiod,”whichwasaboutafewhoursafterhatching,suggestingastrongcriticalperiod.[72] Lorenzalsodiscoveredalong-lastingeffectofhisstudies,andthatwasashiftinthespecies'sexualimprintingasaresultfromimprintinguponafostermotherofasecondspecies.Forcertainspecies,whenraisedbyasecondone,theydevelopandretainimprintedpreferencesandapproachthesecondspeciestheywereraisedbyratherthanchoosetheirown,ifgivenachoice.[73] Imprintingservesasthedistinguishingfactorbetweenone'sownmotherandothermotherfigures.Themotherandtheinfantbothidentifywitheachother,thisisastrongbondingmomentforhumans.Itprovidesasortofmodelorguidetoadultbehaviorsinadditiontootherfactorssuchasnurture,protectionininfancy,guidance,andnourishment.Theimprintingprocess,Lorenzalsofound,broughtaboutasenseoffamiliarityfortheyounganimals.Whensuchastrongbondisformedatsuchanearlystage,itcreatesasenseofsecurityandcomfortforthesubjectandactuallyencouragestheimprintingbehavior. Pheromonesplayakeyroleintheimprintingprocess,theytriggerabiochemicalresponseintherecipient,leadingtoaconfirmedidentificationintheotherindividual.Ifdirectcontactbetweenmotherandinfantisnotmaintainedduringthecriticalimprintingperiod,thenthemothergoosemayrejecttheinfantbecausesheisunfamiliarwithhernewborn'sscent.Ifthatdoeshappen,thentheinfant'slifewouldbeinjeopardyunlessitwereclaimedbyasubstitutemother,possiblyleadingtoawkwardsocialbehaviorinlaterlife.[74]Inrelationtohumans,anewbornduringthecriticalperiodidentifieswithitsmother'sandotherpeoples'scentssinceitsscentisoneofthemostdevelopedsensesatthatstageinlife.Thenewbornusesthispheromoneidentificationtoseekthepeopleitidentifieswith,whenintimesofdistress,hunger,anddiscomfortasasurvivalskill.[75]InferencescouldbemadefornewbornsbaseduponLorenz'sstudies.Whenimprintingontheirmothers,newbornslooktothemfornourishment,asenseofsecurity,andcomfort.Humannewbornsareamongthemosthelplessknownwithorangutangnewbornsrankingsecond.Newbornsofthesespecieshaveaverylimitedarrayofinnatesurvivalabilities.Theirmostimportantandfunctionalabilityistoformbondswithcloseindividualswhoareabletokeepthemalive.Imprintingisacrucialfactorofthecriticalperiodbecauseitfacilitatesthenewborn'sabilitiestoformbondswithotherindividuals,frominfancytoadulthood. Auditoryprocessing[edit] Manystudieshavesupportedacorrelationbetweenthetypeofauditorystimulipresentintheearlypostnatalenvironmentandthedevelopmentonthetopographicalandstructuraldevelopmentoftheauditorysystem.[4] Firstreportsoncriticalperiodscamefromdeafchildrenandanimalsthatreceivedacochlearimplanttorestorehearing.Approximatelyatthesametime,bothanelectroencephalographicstudybySharma,DormanandSpahr[76]andanin-vivoinvestigationofthecorticalplasticityindeafcatsbyKralandcolleagues[77]demonstratedthattheadaptationtothecochlearimplantissubjecttoanearly,developmentalsensitiveperiod.Theclosureofsensitiveperiodslikelyinvolvesamultitudeofprocessesthatintheircombinationmakeitdifficulttoreopenthesebehaviorally.[4]Theunderstandingofthemechanismsbehindcriticalperiodshasconsequencesformedicaltherapyofhearingloss.[78]M.Merzenichandcolleaguesshowedthatduringanearlycriticalperiod,noiseexposurecanaffectthefrequencyorganizationoftheauditorycortex.[79] Recentstudieshaveexaminedthepossibilityofacriticalperiodforthalamocorticalconnectivityintheauditorysystem.Forexample,ZhouandMerzenich(2008)studiedtheeffectsofnoiseondevelopmentintheprimaryauditorycortexinrats.Intheirstudy,ratswereexposedtopulsednoiseduringthecriticalperiodandtheeffectoncorticalprocessingwasmeasured.Ratsthatwereexposedtopulsednoiseduringthecriticalperiodhadcorticalneuronsthatwerelessabletorespondtorepeatedstimuli;theearlyauditoryenvironmentinterruptednormalstructuralorganizationduringdevelopment. Inarelatedstudy,Barkat,PolleyandHensch(2011)lookedathowexposuretodifferentsoundfrequenciesinfluencesthedevelopmentofthetonotopicmapintheprimaryauditorycortexandtheventralmedicalgeniculatebody.Inthisexperiment,micewererearedeitherinnormalenvironmentsorinthepresenceof7 kHztonesduringearlypostnataldays.TheyfoundthatmicethatwereexposedtoanabnormalauditoryenvironmentduringacriticalperiodP11-P15hadanatypicaltonotopicmapintheprimaryauditorycortex.[80] Thesestudiessupportthenotionthatexposuretocertainsoundswithinthecriticalperiodcaninfluencethedevelopmentoftonotopicmapsandtheresponsepropertiesofneurons.Criticalperiodsareimportantforthedevelopmentofthebrainforthefunctionfromapatternofconnectivity.Ingeneral,theearlyauditoryenvironmentinfluencesthestructuraldevelopmentandresponsespecificityoftheprimaryauditorycortex.[81] Musicalability[edit] Mainarticle:Absolutepitch Absolutepitchmanifestsitselfalmostalwaysbeforeadolescenceandrarelyifeveramongindividualswhoarefirstexposedtomusicaftermid-childhood,suggestingthatexposuretomusicorsimilarphenomena(e.g.,tonallanguages)inearlytomid-childhoodisanecessaryconditionforitsdevelopmentorrefinement.Studiesthataskmusiciansandnon-musicianstosingorhumwell-knownpopularsongsthathavedefinitiverecordings(andhencearesunginstandardizedkeys)showthat—onaverage—participantssingwithinasemitoneofthestandardizedkeybutthatoutsidethesmallsubsetofparticipantswithabsolutepitchthereisbroadvariation(the"bellcurve"thatreflectsthedegreeofapproximationtothestandardkeyisbroadandflat).[citationneeded]Theseresultssuggestthatalmostallhumanshavesomeinnateaptitudeforabsolutepitchrecognition—thoughotherfactorsmayenhanceorlimitthelevelofthataptitude.Also,theresults'conjunctionwiththeaforementionedchronologicalobservationssuggeststhatearlytomid-childhoodexposuretoenvironmentswhoseinterpretationdependsonpitchisadevelopmental"trigger"forwhateveraptitudeanindividualpossesses. Vestibularsystem[edit] Inourvestibularsystem,neuronsareundevelopedatneuronalbirthandmatureduringthecriticalperiodofthefirst2-3postnatalweeks.Hence,disruptionofmaturationduringthisperiodcancausechangesinnormalbalanceandmovementthroughspace.Animalswithabnormalvestibulardevelopmenttendtohaveirregularmotorskills.[82] Studieshaveconsistentlyshownthatanimalswithgeneticvestibulardeficienciesduringthiscriticalperiodhavealteredvestibularphenotypes,mostlikelyasaresultofinsufficientinputfromthesemicircularcanalsanddopaminergicabnormalities.Moreover,exposuretoabnormalvestibularstimuliduringthecriticalperiodisassociatedwithirregularmotordevelopment.Childrenwithhypofunctioningvestibularreceptorsfrequentlyhavedelayedmotordevelopment.Theresultsofthestudiesdoneonferretsandratsreinforcedtheideathatthevestibularsystemisveryimportanttomotordevelopmentduringtheinitialneonatalperiod.Ifthevestibularreceptorsarepresentduringtheinitialsixmonthstoayearwhentheinfantislearningtositandstand,thenthechildmaydevelopmotorcontrolandbalancenormally.[83] Thevestibulo-ocularreflex(VOR)isareflexeyemovementthatstabilizesimagesontheretinaduringheadmovement.Itproducesaneyemovementinthedirectionoppositetoheadmovement,thuspreservingtheimageonthecenterofthevisualfield.StudiesinfishandamphibiansrevealedasensitivityintheirVOR.Theylaunchedintospaceflightfor9-10,somewithdevelopingVOR'sandotherswithalreadydevelopedreflexes.Thefishwithdevelopingreflexesdevelopedanupwardbendintheirtails.Thealteredgravityresultedinashiftoforientation.Thosewhowerealreadymaturedwiththereflexwereinsensitivetothemicrogravityexposure.[84] Memory[edit] Recentstudiesalsosupportthepossibilityofacriticalperiodforthedevelopmentofneuronsthatmediatememoryprocessing.Experimentalevidencesupportsthenotionthatyoungneuronsintheadultdentategyrushaveacriticalperiod(about1–3weeksafterneuronalbirth)duringwhichtheyareintegraltomemoryformation.[85]Althoughtheexactreasoningbehindthisobservationisuncertain,studiessuggestthatthefunctionalpropertiesofneuronsatthisagemakethemmostappropriateforthispurpose;theseneurons:(1)Remainhyperactiveduringtheformationofmemories;(2)aremoreexcitable;and(3)MoreeasilydepolarizableduetoGABAergiceffects.Itisalsopossiblethathyperplasticitymakestheneuronsmoreusefulinmemoryformation.Iftheseyoungneuronshadmoreplasticitythanadultneuronsinthesamecontext,theycouldbemoreinfluentialinsmallernumbers.[85] Theroleoftheseneuronsintheadultdentategyrusinmemoryprocessingisfurthersupportedbythefactthatbehavioralexperimentshaveshownthatanintactdentategyrusisintegraltohippocampalmemoryformation.[85]Itisspeculatedthatthedentategyrusactsasarelaystationforinformationrelatingtomemorystorage.Thelikelihoodofacriticalperiodcouldchangethewayweviewmemoryprocessingbecauseitwouldultimatelymeanthatthecollectionofneuronspresentisconstantlybeingreplenishedasnewneuronsreplaceoldones.Ifacriticalperioddoesindeedexist,thiscouldpossiblymeanthat:(1)Diversepopulationsofneuronsthatrepresenteventsoccurringsoonafteroneanothermayconnectthoseeventstemporallyinthememoryformationandprocessing;OR(2)Thesedifferentpopulationsofneuronsmaydistinguishbetweensimilarevents,independentoftemporalposition;OR(3)Separatepopulationsmaymediatetheformationofnewmemorieswhenthesameeventsoccurfrequently.[85] Seealso[edit] Behavioralcusp Childdevelopment Criticalperiodhypothesis Developmentalpsychology Malleableintelligence Universalgrammar References[edit] ^abRobsonAL(2002)."Critical/SensitivePeriods".InSalkindNJ(ed.).ChildDevelopment.GaleVirtualReferenceLibrary.NewYork:MacmillanReferenceUSA.pp. 101–3. ^BrainardMS,KnudsenEI(May1998)."Sensitiveperiodsforvisualcalibrationoftheauditoryspacemapinthebarnowloptictectum".TheJournalofNeuroscience.18(10):3929–42.doi:10.1523/JNEUROSCI.18-10-03929.1998.PMC 6793138.PMID 9570820. ^HenschTK(2004)."Criticalperiodregulation".AnnualReviewofNeuroscience.27:549–79.doi:10.1146/annurev.neuro.27.070203.144327.PMID 15217343. ^abcKralA(September2013)."Auditorycriticalperiods:areviewfromsystem'sperspective".Neuroscience.247:117–33.doi:10.1016/j.neuroscience.2013.05.021.PMID 23707979. ^KnudsenEI,EsterlySD,KnudsenPF(April1984)."Monauralocclusionalterssoundlocalizationduringasensitiveperiodinthebarnowl".TheJournalofNeuroscience.4(4):1001–11.doi:10.1523/JNEUROSCI.04-04-01001.1984.PMC 6564776.PMID 6716127. ^abVyshedskiyA,MahapatraS,DunnR(31August2017)."Linguisticallydeprivedchildren:meta-analysisofpublishedresearchunderlinestheimportanceofearlysyntacticlanguageusefornormalbraindevelopment".ResearchIdeasandOutcomes.3:e20696.doi:10.3897/rio.3.e20696. ^abTallalP,MillerSL,BediG,BymaG,WangX,NagarajanSS,SchreinerC,JenkinsWM,MerzenichMM(January1996)."Languagecomprehensioninlanguage-learningimpairedchildrenimprovedwithacousticallymodifiedspeech".Science.271(5245):81–4.Bibcode:1996Sci...271...81T.doi:10.1126/science.271.5245.81.PMID 8539604.S2CID 2045591. ^abKilgardMP,MerzenichMM(December1998)."Plasticityoftemporalinformationprocessingintheprimaryauditorycortex".NatureNeuroscience.1(8):727–31.doi:10.1038/3729.PMC 2948964.PMID 10196590. ^abcdeTakesianAE,HenschTK(2013)."Balancingplasticity/stabilityacrossbraindevelopment".ProgressinBrainResearch.Elsevier.207:3–34.doi:10.1016/b978-0-444-63327-9.00001-1.ISBN 9780444633279.PMID 24309249. ^abJoliotA,PernelleC,Deagostini-BazinH,ProchiantzA(March1991)."Antennapediahomeoboxpeptideregulatesneuralmorphogenesis".ProceedingsoftheNationalAcademyofSciencesoftheUnitedStatesofAmerica.88(5):1864–8.Bibcode:1991PNAS...88.1864J.doi:10.1073/pnas.88.5.1864.PMC 51126.PMID 1672046. ^abcdHenschTK(November2005)."Criticalperiodplasticityinlocalcorticalcircuits".NatureReviews.Neuroscience.6(11):877–88.doi:10.1038/nrn1787.hdl:10533/174307.PMID 16261181.S2CID 5264124. ^KobayashiY,YeZ,HenschTK(April2015)."Clockgenescontrolcorticalcriticalperiodtiming".Neuron.86(1):264–75.doi:10.1016/j.neuron.2015.02.036.PMC 4392344.PMID 25801703. ^BalmerTS,CarelsVM,FrischJL,NickTA(October2009)."Modulationofperineuronalnetsandparvalbuminwithdevelopmentalsonglearning".TheJournalofNeuroscience.29(41):12878–85.doi:10.1523/JNEUROSCI.2974-09.2009.PMC 2769505.PMID 19828802. ^McRaePA,RoccoMM,KellyG,BrumbergJC,MatthewsRT(May2007)."Sensorydeprivationaltersaggrecanandperineuronalnetexpressioninthemousebarrelcortex".TheJournalofNeuroscience.27(20):5405–13.doi:10.1523/jneurosci.5425-06.2007.PMC 6672348.PMID 17507562. ^YeQ,MiaoQL(August2013)."Experience-dependentdevelopmentofperineuronalnetsandchondroitinsulfateproteoglycanreceptorsinmousevisualcortex".MatrixBiology.32(6):352–63.doi:10.1016/j.matbio.2013.04.001.PMID 23597636. ^abMillerKD,KellerJB,StrykerMP(August1989)."Oculardominancecolumndevelopment:analysisandsimulation".Science.245(4918):605–15.Bibcode:1989Sci...245..605M.doi:10.1126/science.2762813.PMID 2762813. ^ErwinE,MillerKD(December1998)."Correlation-baseddevelopmentofocularlymatchedorientationandoculardominancemaps:determinationofrequiredinputactivities".TheJournalofNeuroscience.18(23):9870–95.doi:10.1523/JNEUROSCI.18-23-09870.1998.PMC 6793311.PMID 9822745. ^HuaJY,SmearMC,BaierH,SmithSJ(April2005)."Regulationofaxongrowthinvivobyactivity-basedcompetition".Nature.434(7036):1022–6.Bibcode:2005Natur.434.1022H.doi:10.1038/nature03409.PMID 15846347.S2CID 4429878. ^abSchafer,DorothyP.(24May2012)."MicrogliaSculptPostnatalNeuralCircuitsinanActivityandComplement-DependentManner".Neuron.74(4):691–705.doi:10.1016/j.neuron.2012.03.026.PMC 3528177.PMID 22632727. ^abSipe,G.O.;et al.(28October2015)."MicroglialP2Y12IsNecessaryforSynapticPlasticityinMouseVisualCortex".NatureCommunications.7:10905.Bibcode:2016NatCo...710905S.doi:10.1038/ncomms10905.PMC 4786684.PMID 26948129. ^Sellgren,CarlM.;et al.(4March2019)."IncreasedSynapseEliminationbyMicrogliainSchizophreniaPatient-DerivedModelsofSynapticPruning".NatureNeuroscience.22(3):374–385.doi:10.1038/s41593-018-0334-7.PMC 6410571.PMID 30718903. ^Dunaevsky,Anna;et al.(7September1999)."DevelopmentalRegulationofSpineMotilityintheMammalianCentralNervousSystem".ProceedingsoftheNationalAcademyofSciences.96(23):13438–13443.Bibcode:1999PNAS...9613438D.doi:10.1073/pnas.96.23.13438.PMC 23966.PMID 10557339. ^Konur,Sila;Yuste,Rafael(1August2003)."DevelopmentalRegulationofSpineandFilopodialMotilityinPrimaryVisualCortex:ReducedEffectsofActivityandSensoryDeprivation".JournalofNeurobiology.59(2):236–246.doi:10.1002/neu.10306.PMID 15085540. ^Majewska,Ania;Mriganka,Sur(27May2003)."MotilityofDendriticSpinesinVisualCortexinVivo:ChangesduringtheCriticalPeriodandEffectsofVisualDeprivation".ProceedingsoftheNationalAcademyofSciences.100(26):16024–16029.Bibcode:2003PNAS..10016024M.doi:10.1073/pnas.2636949100.PMC 307686.PMID 14663137. ^abGangulyK,SchinderAF,WongST,PooM(May2001)."GABAitselfpromotesthedevelopmentalswitchofneuronalGABAergicresponsesfromexcitationtoinhibition".Cell.105(4):521–32.doi:10.1016/S0092-8674(01)00341-5.PMID 11371348.S2CID 8615968. ^FagioliniM,HenschTK(March2000)."Inhibitorythresholdforcritical-periodactivationinprimaryvisualcortex".Nature.404(6774):183–6.Bibcode:2000Natur.404..183F.doi:10.1038/35004582.PMID 10724170.S2CID 4331566. ^HenschTK,FagioliniM,MatagaN,StrykerMP,BaekkeskovS,KashSF(November1998)."LocalGABAcircuitcontrolofexperience-dependentplasticityindevelopingvisualcortex".Science.282(5393):1504–8.doi:10.1126/science.282.5393.1504.PMC 2851625.PMID 9822384. ^HenschTK,StrykerMP(March2004)."ColumnararchitecturesculptedbyGABAcircuitsindevelopingcatvisualcortex".Science.303(5664):1678–81.Bibcode:2004Sci...303.1678H.doi:10.1126/science.1091031.PMC 2562723.PMID 15017001. ^SillitoAM,KempJA,PatelH(1980-12-01)."Inhibitoryinteractionscontributingtotheoculardominanceofmonocularlydominatedcellsinthenormalcatstriatecortex".ExperimentalBrainResearch.41(1):1–10.doi:10.1007/BF00236673.PMID 7461064.S2CID 24537788. ^abKwokJC,CarulliD,FawcettJW(September2010)."Invitromodelingofperineuronalnets:hyaluronansynthaseandlinkproteinarenecessaryfortheirformationandintegrity".JournalofNeurochemistry.114(5):1447–59.doi:10.1111/j.1471-4159.2010.06878.x.PMID 20584105. ^abPizzorussoT,MediniP,BerardiN,ChierziS,FawcettJW,MaffeiL(November2002)."Reactivationofoculardominanceplasticityintheadultvisualcortex".Science.298(5596):1248–51.Bibcode:2002Sci...298.1248P.doi:10.1126/science.1072699.PMID 12424383.S2CID 14254863. ^PizzorussoT,MediniP,LandiS,BaldiniS,BerardiN,MaffeiL(May2006)."Structuralandfunctionalrecoveryfromearlymonoculardeprivationinadultrats".ProceedingsoftheNationalAcademyofSciencesoftheUnitedStatesofAmerica.103(22):8517–22.Bibcode:2006PNAS..103.8517P.doi:10.1073/pnas.0602657103.PMC 1482523.PMID 16709670. ^abHärtigW,DerouicheA,WeltK,BrauerK,GroscheJ,MäderM,ReichenbachA,BrücknerG(September1999)."CorticalneuronsimmunoreactiveforthepotassiumchannelKv3.1bsubunitarepredominantlysurroundedbyperineuronalnetspresumedasabufferingsystemforcations".BrainResearch.842(1):15–29.doi:10.1016/S0006-8993(99)01784-9.PMID 10526091.S2CID 19980614. ^VoT,CarulliD,EhlertEM,KwokJC,DickG,MecollariV,MoloneyEB,NeufeldG,deWinterF,FawcettJW,VerhaagenJ(September2013)."Thechemorepulsiveaxonguidanceproteinsemaphorin3Aisaconstituentofperineuronalnetsintheadultrodentbrain".MolecularandCellularNeurosciences.56:186–200.doi:10.1016/j.mcn.2013.04.009.PMID 23665579.S2CID 21526309. ^HartlineDK,ColmanDR(January2007)."Rapidconductionandtheevolutionofgiantaxonsandmyelinatedfibers".CurrentBiology.17(1):R29-35.doi:10.1016/j.cub.2006.11.042.PMID 17208176.S2CID 10033356. ^abcHolmesGL,MilhMD,DulacO(2012)."Maturationofthehumanbrainandepilepsy".HandbookofClinicalNeurology.Elsevier.107:135–43.doi:10.1016/b978-0-444-52898-8.00007-0.ISBN 9780444528988.PMID 22938967. ^abcdMcGeeAW,YangY,FischerQS,DawNW,StrittmatterSM(September2005)."Experience-drivenplasticityofvisualcortexlimitedbymyelinandNogoreceptor".Science.309(5744):2222–6.Bibcode:2005Sci...309.2222M.doi:10.1126/science.1114362.PMC 2856689.PMID 16195464. ^abcYiuG,HeZ(August2006)."GlialinhibitionofCNSaxonregeneration".NatureReviews.Neuroscience.7(8):617–27.doi:10.1038/nrn1956.PMC 2693386.PMID 16858390. ^abcMakinodanM,RosenKM,ItoS,CorfasG(September2012)."Acriticalperiodforsocialexperience-dependentoligodendrocytematurationandmyelination".Science.337(6100):1357–60.Bibcode:2012Sci...337.1357M.doi:10.1126/science.1220845.PMC 4165613.PMID 22984073. ^SánchezMM,HearnEF,DoD,RillingJK,HerndonJG(November1998)."Differentialrearingaffectscorpuscallosumsizeandcognitivefunctionofrhesusmonkeys".BrainResearch.812(1–2):38–49.doi:10.1016/s0006-8993(98)00857-9.PMID 9813233.S2CID 23976772. ^HenschTK(January2014)."Bistableparvalbumincircuitspivotalforbrainplasticity".Cell.156(1–2):17–9.doi:10.1016/j.cell.2013.12.034.PMC 4183967.PMID 24439367. ^FrémauxN,GerstnerW(2015)."NeuromodulatedSpike-Timing-DependentPlasticity,andTheoryofThree-FactorLearningRules".FrontiersinNeuralCircuits.9:85.doi:10.3389/fncir.2015.00085.PMC 4717313.PMID 26834568. ^abcdeKilgardMP,MerzenichMM(March1998)."Corticalmapreorganizationenabledbynucleusbasalisactivity".Science.279(5357):1714–8.Bibcode:1998Sci...279.1714K.doi:10.1126/science.279.5357.1714.PMID 9497289. ^abcdeBaoS,ChanVT,MerzenichMM(July2001)."Corticalremodellinginducedbyactivityofventraltegmentaldopamineneurons".Nature.412(6842):79–83.Bibcode:2001Natur.412...79B.doi:10.1038/35083586.PMID 11452310.S2CID 4353142. ^abcdefghYaegerCE,RingachDL,TrachtenbergJT(March2019)."Neuromodulatorycontroloflocalizeddendriticspikingincriticalperiodcortex".Nature.567(7746):100–104.Bibcode:2019Natur.567..100Y.doi:10.1038/s41586-019-0963-3.PMC 6405296.PMID 30787434. ^abAveryMC,KrichmarJL(2017-12-22)."NeuromodulatorySystemsandTheirInteractions:AReviewofModels,Theories,andExperiments".FrontiersinNeuralCircuits.11:108.doi:10.3389/fncir.2017.00108.PMC 5744617.PMID 29311844. ^abLeveltCN,HübenerM(2012-07-21)."Critical-periodplasticityinthevisualcortex".AnnualReviewofNeuroscience.35(1):309–30.doi:10.1146/annurev-neuro-061010-113813.PMID 22462544. ^abBearMF,SingerW(March1986)."Modulationofvisualcorticalplasticitybyacetylcholineandnoradrenaline".Nature.320(6058):172–6.Bibcode:1986Natur.320..172B.doi:10.1038/320172a0.PMID 3005879.S2CID 29697125. ^abcdefgTakesianAE,BogartLJ,LichtmanJW,HenschTK(February2018)."Inhibitorycircuitgatingofauditorycritical-periodplasticity".NatureNeuroscience.21(2):218–227.doi:10.1038/s41593-017-0064-2.PMC 5978727.PMID 29358666. ^WeikumWM,OberlanderTF,HenschTK,WerkerJF(October2012)."Prenatalexposuretoantidepressantsanddepressedmaternalmoodaltertrajectoryofinfantspeechperception".ProceedingsoftheNationalAcademyofSciencesoftheUnitedStatesofAmerica.109Suppl2(Supplement_2):17221–7.doi:10.1073/pnas.1121263109.PMC 3477387.PMID 23045665. ^abcPiHJ,HangyaB,KvitsianiD,SandersJI,HuangZJ,KepecsA(November2013)."Corticalinterneuronsthatspecializeindisinhibitorycontrol".Nature.503(7477):521–4.Bibcode:2013Natur.503..521P.doi:10.1038/nature12676.PMC 4017628.PMID 24097352. ^abcSiegler,Robert(2006).HowChildrenDevelop,ExploringChildDevelopStudentMediaToolKit&ScientificAmericanReadertoAccompanyHowChildrenDevelop.NewYork:WorthPublishers.ISBN 0-7167-6113-0. ^CurtissS(1977).Genie:apsycholinguisticstudyofamodern-daywildchild.NewYork:AcademicPress. ^NewportEL(1990)."Maturationalconstraintsonlanguagelearning".CognitiveScience.14(1):11–28.doi:10.1207/s15516709cog1401_2. ^MayberryRI,LockE,KazmiH(May2002)."Linguisticabilityandearlylanguageexposure".Nature.417(6884):38.Bibcode:2002Natur.417...38M.doi:10.1038/417038a.PMID 11986658.S2CID 4313378. ^Johnson,Eric."First-LanguageAcquisition."EncyclopediaofBilingualEducation.Ed.JosuéM.González.Vol.1.ThousandOaks,CA:SAGEPublications,2008.299-304.GaleVirtualReferenceLibrary.Web.22Oct.2014. ^PinkerS(1994).TheLanguageInstinct.NewYork:Morrow. ^DeKeyserRM(2000-12-01)."TheRobustnessofCriticalPeriodEffectsinSecondLanguageAcquisition".StudiesinSecondLanguageAcquisition.22(4):499–533.doi:10.1017/S0272263100004022.ISSN 1470-1545. ^abJia,Li."LearningaLanguage,BestAge."EncyclopediaofBilingualEducation.Ed.JosuéM.González.Vol.1.ThousandOaks,CA:SAGEPublications,2008.520-523.GaleVirtualReferenceLibrary.Web.20Oct.2014. ^SnowCE,Hoefnagel-HöhleM(December1978)."TheCriticalPeriodforLanguageAcquisition:EvidencefromSecond-LanguageLearning".ChildDevelopment.49(4):1114–1128.doi:10.1111/j.1467-8624.1978.tb04080.x.JSTOR 1128751. ^BirdsongD(1999).SecondLanguageAcquisitionandtheCriticalPeriodHypothesis.Routledge.ISBN 9781135674892. ^JohnsonJS,NewportEL(January1989)."Criticalperiodeffectsinsecondlanguagelearning:theinfluenceofmaturationalstateontheacquisitionofEnglishasasecondlanguage".CognitivePsychology.21(1):60–99.doi:10.1016/0010-0285(89)90003-0.PMID 2920538.S2CID 15842890. ^PallierC,DehaeneS,PolineJB,LeBihanD,ArgentiAM,DupouxE,MehlerJ(February2003)."Brainimagingoflanguageplasticityinadoptedadults:canasecondlanguagereplacethefirst?"(PDF).CerebralCortex.13(2):155–61.doi:10.1093/cercor/13.2.155.PMID 12507946. ^WhiteL,GeneseeF(1996-01-01)."Hownativeisnear-native?Theissueofultimateattainmentinadultsecondlanguageacquisition".SecondLanguageResearch.12(3):233–265.doi:10.1177/026765839601200301.JSTOR 43104516.S2CID 146433640. ^JanciauskasM,ChangF(May2018)."InputandAge-DependentVariationinSecondLanguageLearning:AConnectionistAccount".CognitiveScience.42Suppl2:519–554.doi:10.1111/cogs.12519.PMC 6001481.PMID 28744901. ^WieselTN,HubelDH(November1963)."Effectsofvisualdeprivationonmorphologyandphysiologyofcellinthecat'slateralgeniculatebody".JournalofNeurophysiology.26(6):978–93.doi:10.1152/jn.1963.26.6.978.PMID 14084170.S2CID 16117515. ^ExperimentModule:EffectsofVisualDeprivationDuringtheCriticalPeriodforDevelopmentofVision.McGillUniversity,TheBrainfromToptoBottom ^AntoniniA,StrykerMP(June1993)."Rapidremodelingofaxonalarborsinthevisualcortex".Science.260(5115):1819–21.Bibcode:1993Sci...260.1819A.doi:10.1126/science.8511592.JSTOR 2881379.PMID 8511592. ^Manwithrestoredsightprovidesnewinsightintohowvisiondevelops ^OutOfDarkness,Sight:RareCasesOfRestoredVisionRevealHowTheBrainLearnsToSee ^HigleyMJ,StrittmatterSM(November2010)."Neuroscience.Lynxforbrakingplasticity".Science.330(6008):1189–90.Bibcode:2010Sci...330.1189H.doi:10.1126/science.1198983.PMC 3244692.PMID 21109660. ^KisilevskyBS,HainsSM,LeeK,XieX,HuangH,YeHH,ZhangK,WangZ(May2003)."Effectsofexperienceonfetalvoicerecognition".PsychologicalScience.14(3):220–4.doi:10.1111/1467-9280.02435.PMID 12741744.S2CID 11219888. ^MertzLA."ImprintingandEstablishmentofEthology".GaleVirtualReferenceLibrary.NeilSchlagerandJoshLauer.Retrieved20October2014. ^HollarDW."Imprinting".SalemHealth:Psychology&MentalHealth.3:980–984. ^StoneSM."Imprinting".GaleVirtualReferenceLibrary.SAGEReference.Retrieved20October2014. ^SharmaA,DormanMF,SpahrAJ(2002)."Asensitiveperiodforthedevelopmentofthecentralauditorysysteminchildrenwithcochlearimplants:implicationsforageofimplantation".EarHear.23(6):532–29.doi:10.1097/00003446-200212000-00004.PMID 12476090.S2CID 14004538. ^KralA,HartmannR,TilleinJ,HeidS,KlinkeR(August2002)."Hearingaftercongenitaldeafness:centralauditoryplasticityandsensorydeprivation".CerebralCortex.12(8):797–807.doi:10.1093/cercor/12.8.797.PMID 12122028. ^KralA,SharmaA(February2012)."Developmentalneuroplasticityaftercochlearimplantation".TrendsinNeurosciences.35(2):111–22.doi:10.1016/j.tins.2011.09.004.PMC 3561718.PMID 22104561. ^NakaharaH,ZhangLI,MerzenichMM(May2004)."Specializationofprimaryauditorycortexprocessingbysoundexposureinthe"criticalperiod"".ProceedingsoftheNationalAcademyofSciencesoftheUnitedStatesofAmerica.101(18):7170–4.Bibcode:2004PNAS..101.7170N.doi:10.1073/pnas.0401196101.PMC 406484.PMID 15118079. ^BarkatTR,PolleyDB,HenschTK(July2011)."Acriticalperiodforauditorythalamocorticalconnectivity".NatureNeuroscience.14(9):1189–94.doi:10.1038/nn.2882.PMC 3419581.PMID 21804538. ^ZhouX,MerzenichMM(March2008)."Enduringeffectsofearlystructurednoiseexposureontemporalmodulationintheprimaryauditorycortex".ProceedingsoftheNationalAcademyofSciencesoftheUnitedStatesofAmerica.105(11):4423–8.Bibcode:2008PNAS..105.4423Z.doi:10.1073/pnas.0800009105.PMC 2393777.PMID 18332439. ^EugèneD,DeforgesS,VibertN,VidalPP(May2009)."Vestibularcriticalperiod,maturationofcentralvestibularneurons,andlocomotorcontrol".AnnalsoftheNewYorkAcademyofSciences.1164(1):180–7.Bibcode:2009NYASA1164..180E.doi:10.1111/j.1749-6632.2008.03727.x.PMID 19645897.S2CID 24833800. ^VanCleaveS,ShallMS(2006)."Acriticalperiodfortheimpactofvestibularsensationonferretmotordevelopment".JournalofVestibularResearch.16(4–5):179–86.PMC 2034323.PMID 17538206. ^HornER(May2004).""Criticalperiods"investibulardevelopmentoradaptationofgravitysensorysystemstoalteredgravitationalconditions?".ArchivesItaliennesdeBiologie.142(3):155–74.PMID 15260375. ^abcdAasebøIE,BlankvoortS,TashiroA(March2011)."Criticalmaturationalperiodofnewneuronsinadultdentategyrusfortheirinvolvementinmemoryformation".TheEuropeanJournalofNeuroscience.33(6):1094–100.doi:10.1111/j.1460-9568.2011.07608.x.PMID 21395853.S2CID 37671329. Externallinks[edit] Bibliographyofpapersoncriticalperiodsinsecondlanguageacquisition Retrievedfrom"https://en.wikipedia.org/w/index.php?title=Critical_period&oldid=1054970884" Categories:DevelopmentalbiologyDevelopmentalpsychologyHiddencategories:CS1:longvolumevalueArticleswithshortdescriptionShortdescriptionisdifferentfromWikidataAllarticleswithunsourcedstatementsArticleswithunsourcedstatementsfromApril2016 Navigationmenu Personaltools NotloggedinTalkContributionsCreateaccountLogin Namespaces ArticleTalk English Views ReadEditViewhistory More Search Navigation MainpageContentsCurrenteventsRandomarticleAboutWikipediaContactusDonate Contribute HelpLearntoeditCommunityportalRecentchangesUploadfile Tools WhatlinkshereRelatedchangesUploadfileSpecialpagesPermanentlinkPageinformationCitethispageWikidataitem Print/export DownloadasPDFPrintableversion Languages العربيةČeštinaEspañolFrançaisעבריתSuomiУкраїнська Editlinks



請為這篇文章評分?