Critical Period In Brain Development and ... - Parenting For Brain

A critical period is a phase during which the brain cell connections are more plastic and receptive to the influence of a certain kind of life ... SkiptoContent Findoutwhatacriticalperiodisinbraindevelopmentandhowparentscanusethisknowledgetopromoteoptimalbraingrowthinourchildren. TableofContents WhatisCriticalPeriod CriticalPeriodHypothesis SensitivePeriod WhyisCriticalPeriodImportant CriticalPeriodforLanguageAcquisition WhatisCriticalPeriod Acriticalperiodisaphaseduringwhichthebraincellconnectionsaremoreplasticandreceptivetotheinfluenceofacertainkindoflifeexperience.Theseconnections,calledsynapses,canformorstrengthenmoreeasilyduringthisperiod.Synapticconnectionsusuallymatureandchangesstabilizeafterthiswindowoftimeandthewiringsbecomehardertochange. CriticalPeriodHypothesis AccordingtotheCriticalPeriodHypothesis,duringthecriticalperiod,anewskillortraitcanbeformedgiventheproperlifeexperience.Ifthenecessaryexperienceisnotavailableduringthistime,itbecomesmuchharder,lesssuccessfulorevenimpossibletoacquiretheskillortraitafterthewindowofopportunitycloses. Thisisproventrueinsensorysystemsinhumanandanimals,suchasvisionandhearing. Forexample,ifoneeye(butnotboth)iscoveredrightafterbirth,thedeprivedeyewilllosevisualacuitypermanently,evenifthecoveredperiodisbriefpostnatal.Thisisbecausecoveringaneyeduringthecriticalperiodcanalterthephysicalpathwaysofthebrainpermanently​1​. CriticalPeriodvsSensitivePeriod Asensitiveperiodissimilartoacriticalperiodinwhichthebrainisrelativelymoreplasticandmoresensitivetotheinfluenceofexperienceinformingnewsynapses.Newsynapsescanstillformforanextendedperiodoftimeoutsideofthisoptimalperioddespitebeingmoredifficult. Somescientistsrefertothisasaweakcriticalperiod. Formorehelponcalmingtantrums,checkoutthisstep-by-stepguide WhyIsCriticalPeriodImportant Criticalperiodsareimportantbecausemanycrucialfunctionsofourbodyareestablishedduringthoseperiods,andsomeonlyduringthoseperiods. Studieshavefoundthatthefollowingfunctionsarebestdevelopedduringtheircriticalperiods. Emotionalregulation Emotionalselfregulationistheabilitytomonitorandmodulateemotions.Learningtoself-regulateisakeymilestoneinachild’sdevelopment.Itcansignificantlyimpactachild’srelationships,academicperformance,mentalhealthandlong-termwell-being. InastudyinaRomanianorphanage,onlyorphanswhowereadoptedbyfosterfamiliesbeforetheageof2wereabletodevelopemotionalregulationskillscomparabletothoseoftheneverinstitutionalizedchildren​6​.Thosewhoremainedintheorphanagesufferedfromdeprivationofsocialcontactormaternalcare,andgrewuplackingemotionalregulationlaterinlife. Thesensitiveperiodofemotionalself-regulationisthereforebelievedtobefrombirthtoage2. VisionSystem Therearedifferentcriticalperiodsfordifferentvisualfunctionsofthevisualsystem.Theyusuallyfallbetweeneye-openingandpuberty​7​. Forexample,researchresultsshowthatvisualacuityusuallydevelopsfrombirthtoaroundage5andtheperiodbetweenages3and5showsthemostgrowth.Ontheotherhand,stereopsis,theperceptionofdepth,hasacriticalperiodthatendsat2yearsofage. Susceptibilitytodamageinvisualdevelopmentalsohasitsowncriticalperiod.Forinstance,amblyopia,theconditionwhereoneoftheeyeshasreducedvisionbecausetheeyeandbrainarenotworkingtogetherproperly,canresultbetweenseveralmonthsoldand7or8yearsofage. AbsolutePitchinMusicListening Absolutepitchistheabilitytoidentifyandproducethepitchofamusicalsoundwithoutanexternalsoundsasreferencepoints​8​. Childrenwhostartedmusicaltrainingbetweenages4and6aremostlikelytoreachtheabsolutepitch. Buttrainingsthatoccuraftertheageof9rarelyleadstothatlevelofproficiency​9​inadult. AuditoryProcessing Forchildrenwhoarebornwithcongenitaldeafness,theabsenceofauditoryinputfrombirthcanaffectthenormalgrowthofafunctionalauditorysystem,severelyaffectingtheirabilitytolearntospeak. Scientistshavefoundthatwhencochlearimplantsareinstalledtobypassthenon-functionalinnerearsinthesechildrenbeforeage3.5,theycanmostlikelylearntospeaksuccessfully,especiallyiftheyarealsoexposedtolanguage-richenvironments​10​. CriticalPeriodForLanguageAcquisition Whenappliedtolanguagelearning,theCriticalPeriodHypothesisstatesthatthereisacriticaltimeduringwhichindividualsaremorecapableofacquiringnewlanguageswithnative-likeproficiency. Thisperiodbeginsinearlychildhoodandconcludesshortlybeforetheonsetofpuberty​2​. Afterthiswindow,evenwithalinguisticallyrichenvironment,itbecomesmuchmoredifficulttoacquirenewlanguagecompetency​3​andfullmasteryisunlikely. TheoriginalhypothesiswasfirstpopularizedbyEricLenneberg,alinguistandneurologist,inalandmarkbookBiologicalFoundationsofLanguagein1967. Accordingtothistheory,theprocessoflearninganewlanguageisconstrainedbyacriticalperiod.Thereisadistinctdiscontinuityinoutcomesbetweenlearningwithinthecriticalperiodandlearningoutsideofit.Thetimeofthatdiscontinuityreflectsthecloseofthecriticalperiod​4​. However,weknowthatitisstillpossibleforadultstolearntouseanewlanguagebeyondpuberty,althoughit’sharderandmaytakelongercomparedtoyoungchildren. Thus,learningperfectphonologyandgrammarinasecondlanguagehasacriticalperiod,butlearning(asgeneralspeakers)seemstohavemoreasensitiveperiodratherthanacriticalperiod(althoughthisalternativedefinitionisstillcontroversial​5​andindividualeffectdoesvary). WhatParentsShouldKnow Itmayfeeloverwhelmingthattherearesomanydifferentcriticalperiodsinthebraindevelopmentjourney. Parentswhohave“missed”someofthecriticalperiodsareworriedthattheirchildrenarenowdestinedtofail.Thosewhohave“met”thecriticalperiodssuccessfullyaregladthattheirchildrenarenowsetforlifeandtheirjobsaredone. Thetruthisthatneitherofthesearetrue. Criticalperiodisacontroversialscienceconceptbecauseitimpliesthereisahardcutoff.Iftheskillisnotdevelopedduringthattime,theopportunitytodevelopthisfunctionwillbegoneforever. Butsomeofthoseskillsareactuallyexperience-expectantratherthanexperience-dependent,meaningthestimulirequiredfordevelopmentareexpected.Theexpectedexperiencesarepracticallyguaranteedtobeavailableineverydaylife,e.g.thecapacityforlanguage,vision,andhearing.Parentsrarelyhavetomakeanefforttointroducethosecommonexperiences. Abilitiesthatdependonthepresenceofspecificexperiencesareexperience-dependent.Parentsneedtoprovidetheappropriateearlylifeexperiencesfortheseskillstodevelop.Someexamplesareemotionalregulation,speech&language,andtheabsolutepitch. Butthegoodnewsismanyexperience-dependenttraitshavesensitiveperiodsratherthancriticalperiods.Evenwhentheparticularlifeexperiencesaremissingduringtheoptimaltime,theskillscanstilldevelop.Itmightjustbeharderortakelonger. Amongtheexperience-dependentabilities,emotionalregulationishandsdownthemostessentialonetoachild’sgrowthandfuturewell-being.Sothemostimportantthingforparentstodoistoprovideanurturingenvironmentforyourchildandhelpyourchildbuildresilience. FinalThoughtsOnCriticalPeriod Asparents,it’sbetterifwemakesureourchildrenarenotdeprivedofcriticalexperiences,especiallyduringcriticalperiods.However,itdoesn’tmeanweshouldbuythelatest“mozartforbabies”DVDorsignourtoddlersupindozesofenrichmentclasses.Whatourchildrenneedareanurturingenvironmentandexposuretocommonlifeexperiences,suchastalking,playingandreadingtothem.Also,otherunderlyingfactorscouldaffecttheoutcomes,too. Thereisalsononeedtosweatovermissingtheoptimaltimes,becauseit’snevertoolatetostartprovidinggoodlifeexperiencestoourkids. References 1.HenschTK.Criticalperiodplasticityinlocalcorticalcircuits.NatRevNeurosci.November2005:877-888.doi:10.1038/nrn1787 2.HakutaK,BialystokE,WileyE.CriticalEvidence.PsycholSci.January2003:31-38.doi:10.1111/1467-9280.01415 3.FriedericiAD,SteinhauerK,PfeiferE.Brainsignaturesofartificiallanguageprocessing:Evidencechallengingthecriticalperiodhypothesis.ProceedingsoftheNationalAcademyofSciences.January2002:529-534.doi:10.1073/pnas.012611199 4.BirdsongD.SecondLanguageAcquisitionandtheCriticalPeriodHypothesis.Routledge;1999. 5.BirdsongD,MolisM.OntheEvidenceforMaturationalConstraintsinSecond-LanguageAcquisition.JournalofMemoryandLanguage.February2001:235-249.doi:10.1006/jmla.2000.2750 6.McLaughlinKA,SheridanMA,TibuF,FoxNA,ZeanahCH,NelsonCAIII.Causaleffectsoftheearlycaregivingenvironmentondevelopmentofstressresponsesystemsinchildren.ProcNatlAcadSciUSA.April2015:5637-5642.doi:10.1073/pnas.1423363112 7.DawNW.CriticalPeriodsandAmblyopia.ArchOphthalmol.April1998:502.doi:10.1001/archopht.116.4.502 8.LevitinDJ,RogersSE.Absolutepitch:perception,coding,andcontroversies.TrendsinCognitiveSciences.January2005:26-33.doi:10.1016/j.tics.2004.11.007 9.GervainJ,VinesBW,ChenLM,etal.Valproatereopenscritical-periodlearningofabsolutepitch.FrontSystNeurosci.2013.doi:10.3389/fnsys.2013.00102 10.KralA,SharmaA.Developmentalneuroplasticityaftercochlearimplantation.TrendsinNeurosciences.February2012:111-122.doi:10.1016/j.tins.2011.09.004 Wasthisarticlehelpful? 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