Name
ThetermhippocampuscomesfromLatin(Hippocampus),anditisnamedbecausetheshapeofthestructureissimilartothatofthehippocampus.
Anatomy
Thehippocampusstructureiscomposedofthehippocampusandthedentategyrusandinferiorpedicleadjacenttothetemporallobe.Inaddition,thehippocampusincludestheentorhinalareainsidetheparahippocampalgyrus.
Fromananatomicalpointofview,thehippocampusisoftenseenasamedialbulgeofthetemporalhornofthelateralventricle.ItiscomposedoffourareasCA1,CA2,CA3andCA4.
Wheninformationentersthehippocampus,itflowsfromthedentategyrusintoCA3andthenpassesthroughCA1tothesubbrasalhead.Additionalinformationisinputineachareaandoutputinthelasttwoareas.
Itisgenerallybelievedthatdifferentregionsplayauniqueroleintheinformationprocessingprocessofthehippocampus,butsofarthespecificfunctionsofeachregionstillneedtobefurtherstudied.
Memoryfunction
Amnesia(amnesia)ismainlymanifestedasthelossofmemoryability.In1957,ScovilleandMilnerreportedaveryimportantcaseinneuropsychology.ThisisareportfromapatientcalledHM.Duetolong-termepilepsysymptoms,thedoctordecidedtoperformsurgeryonhim.Thelimbicsystemtissueunderthetemporalcortexwasremoved,includingthehippocampusonbothsides.Thesymptomsofpost-epilepsywereeffectivelycontrolled,butsincethen,HMhasdevelopedanterogradeamnesiaandlosttheabilitytoformnewdeclarativelong-termmemory.H.M.'sshort-termmemoryabilityandimplicitmemoryabilityremainedbetter,whilethestorageoflong-termmemoryandtheabilityofepisodicmemoryweregreatlyimpaired.
However,theresultsofstudiesonHMandotherhippocampalinjurypatientsonlyprovedthatthehippocampushasaneffectonmemory.Inordertofurtherverifytheexactroleofthehippocampusinmemorygeneration,theresearchersfurtherproveditsrolethroughanimalexperiments.
TheAmericanBiotechnologyNetworkreportedonJune10,2003thatscientistsfromHarvardUniversityandNewYorkUniversity(NYU)jointlydiscoveredtheoperatingmechanismofthehippocampusofthebrain—thehippocampusofthebrainhelpsHumanbeingsarethemainareasforlong-termlearningandmemoryofeventssuchassoundandlight,taste,etc.(namely,narrativememory).Bystudyingtheactivityofneuronsinthehippocampus,researchershavediscoveredamethodfortheformationofnarrativememoriesinthebrain.Thisdiscoveryalsoprovidesthemostfavorableevidencefortheplasticityofmemorylearninginthehippocampus.Sincethe1950s,scientistshavenoticedtherelationshipbetweenthehippocampusofthebrainandmemory.Butithasnotbeenabletoconnectmemorywithneuralactivityinthehippocampus.Ifthehippocampusisremoved,thepreviousmemorieswilldisappeartogether.Buttheproblemof"howdothenervecellsinthehippocampusfixtheinformation"hasnotbeenresolved.Scientistshavediscoveredthatsomemoleculesareinvolvedintheformationofmemories.Inaddition,theformationofsynapsesinnervecellsisalsoassociatedwithmemory.However,scientistsstilldonothaveenoughunderstandingoftheoperatingmechanismofmemory-andthismechanismisveryimportantforunderstandingourselves.ResearchersatNewYorkUniversityusedelectrodestomonitortheneuronalactivityofthemonkey'sbrainduringlearning.Thenusethe"dynamicestimationalgorithms"developedbyHarvardUniversityresearcherstoanalyzetherecordedbehaviorandneuralinformation.
Duringthecourseofthestudy,theresearchersaskedthemonkeystowatchcompleximagessuperimposedbyfouranalogueseveryday.Whenthemonkeyknowsthelocationofeachimagefromtrialanderrorlearning,itcanberewarded.Atthesametime,theresearchersobservedtheactivityofneuronsinthehippocampusofmonkeys,andtheyfoundthatsomeofthechangesincellneuralactivitywereparalleltothelearningcurveofmonkeys.Thismeansthattheseneuronsareinvolvedintheformationofnewassociativememories.Andbecausetheseneuralactivitiescontinuetocontinueafterthemonkeystopslearning,theresearchersspeculatethatsomeofthecellsshouldberelatedtotheformationoflong-termmemory.
Thestorageandprocessingofspatialinformationisalsorelatedtothehippocampus.Inafunctionalmagneticresonancestudy,whensubjectswereaskedtoimaginethebestroutebetweenthehomesoftwofriends,theactivitylevelofthehippocampuswassignificantlyhigherthanthebaselinestate(Kumaran&Maguire,2005)Inthedriver-relatedresearch,whenaskingquestionssuchas"HowtogetthebestroutefromCatonCastleHoteltoSherlockHolmesMuseum"isequaltospatialinformation,theresultsofPETscanshowedthattheactivationlevelofthehippocampuswasmuchhigherthanthatofotherquestions.Inaddition,magneticresonanceimagingstudieshavealsoconfirmedthatthehippocampusoftaxidriversislargerthanthatofordinaryindividuals,andispositivelycorrelatedwithdrivingage.
Inaddition,thehippocampusisrelatedtoenvironmentalbackgroundmemory,andthehippocampusisTheenvironmentalbackgroundanddetailsoftheeventalsoplayaveryimportantroleinthememory.Fortherecenttime,manydetailsareusuallycompletedbythehippocampus.Astimegoesby,thememorydetailswilldecrease,andthehippocampus’Theeffectisalsogettingsmallerandsmaller.Inthestudyofrats,theratswereallowedtolearnabehavioralresponseandthentestedit.Ifthetestenvironmentissimilartotheoriginalenvironment,thememoryeffectwillbebetter.AndhippocampusdamageRatsdidnotshowsuchenvironmental-specificdifferences.
Consolidationofmemory
Thehippocampusplaysanimportantroleinconsolidatingshort-termmemoryandtransformingmemoriesduringgrowthInanexperiment,adrugthatpreventsproteinsynthesiswasinjectedintothehippocampusofrats.Thelearningabilityofratsdidnotshowobviousimpairment.Butcomparedwithnormalrats,thecontentoflearningAftertwodays,theywereallforgotten.Obviously,thisproteininhibitorysyntheticagentpreventstheconsolidationprocessofmemory.Intheprocessofmemoryconsolidation,thelong-termenhancementeffectplaysanimportantrole,thelong-termenhancementeffect,alsoknownasthelong-termgaineffect(Long-termpotentiation,LTP)isalastingenhancementphenomenonthatoccursinthesignaltransmissionoftwoneurons,whichcanstimulatetwoneuronssimultaneously.Thisisrelatedtosynapticplasticity-theabilityofsynapsestochangestrengthOneofseveralphenomena.Sincememoryisthoughttobeencodedbychangesinsynapticstrength,LTPisgenerallyregardedasoneofthemainmolecularmechanismsthatformthebasisoflearningandmemory.
Role
Generalmemoryfunction
Psychologistsandneurologistshavedisputesabouttheroleofthehippocampus,buttheyallagreethattheimportantroleofthehippocampusistoformnewmemories(episodicmemoryorautobiography).Sexualmemory).Somescholarsbelievethatthehippocampusshouldberegardedaspartofthemedialtemporallobememorysystemthatplaysaroleingeneraldeclarativememory(declarativememoryreferstomemoriesthatcanbeclearlydescribed,suchas"Whatdidyoueatfordinneryesterday?""Suchepisodicmemoryofpastevents,andconceptualmemoryofknowledgesuchas"theearthisround").
Therearesignsthatalthoughtheseformsofmemoryusuallylastforlife,Afteraseriesofmemoryenhancement,thehippocampusceasestoretainmemory.Damagetothehippocampusoftenmakesitdifficulttoorganizenewmemories(anterogradeamnesia),anditalsomakesitdifficulttosearchpastmemories(retrogradeamnesia).Althoughsuchretrogradeeffectsusuallybegintoexpandmanyyearsbeforethebraininjury,insomecasesrelativelylongmemoriescanbemaintained.Thisshowsthatthehippocampuswillconsolidatethememorytotransfertootherpartsofthebrain.However,therearesomedifficultiesintestinghowoldmemoriesarestored.Inaddition,insomecasesofretrogradeamnesia,thememoryofdecadesbeforethehippocampuswasdamagedhasalsobeenaffected,whichhasledtothiscontroversyovertheviewofoldmemories.
Thedamageofthehippocampuswillnotaffectcertainmemories,suchastheabilitytolearnnewskills(suchaslearningamusicalinstrument).Thisabilitywillrelyonanotherkindofmemory(programmemory)anddifferentBrainarea.Therearesignsthatthewell-knownpatientHM(hismedialtemporallobewasremovedasatreatmentforepilepsy)hastheabilitytoorganizethememoryofnewconcepts.
Theroleoforientationandpositioning
Someevidenceprovidesthefollowingclues:Thestorageandprocessingofspatialinformationinvolvesthehippocampus.Studiesinmicehaveshownthatneuronsinthehippocampushavespatialdischargeareas,andthesecellsarecalledplacecells.Ifamousefindsitselfinacertainplace,nomatterwhatdirectionthemouseismoving,somecellswillgenerateelectricity,andmostofthecellswillatleastbesensitivetothedirectionoftheheadandthedirectionofmovement.Inmice,somecellsarecalledsplittercells.Thepowergenerationofthesecellsdependsontheanimal'srecentexperience(retrospectivememory)orlookingforwardtothefuture(prospectivememory).Accordingtodifferentlocations,differentcellsgenerateelectricity;therefore,aslongasyouobservethepowergenerationofcells,youcanpointoutwheretheanimalis.Inhumans,whenpeoplearelookingforadirectioninatowninthevirtualworld,the"locationcell"isinvolved.Thisdiscoverystemsfromthefollowingresearch:implantingelectrodesinthebrainsofpatientswithsevereepilepsyasawaytodiagnosepatientsduringsurgery.
Thediscoveryof"locationcells"makestheworldfeelthatthehippocampusmayplaytheroleofa"cognitivemap",andthecognitivemapistheneuralreproductionoftheenvironmentalpattern.However,inresponsetothisview,recentevidenceraisesdoubtsandpointsoutthatthehippocampusisveryimportantforthemorefundamentalprocessof"navigation."Nevertheless,animalexperimentshaveshownthatahealthyhippocampusisnecessaryeventocompletesimplespatialmemoryactivities(suchashidingthedestinationandaskingtheanimaltofindawayback).
Ifthehippocampusisnothealthy,humansmaynotbeabletorememberwheretheyhavebeenandhowtogettowheretheywanttogo.Researchersbelievethatthehippocampusplaysanextremelyimportantroleinfindingshortcutsandnewroutesbetweenfamiliarenvironments.Fortheabilitytofinddirections,somepeoplearebetterthanothers;inaddition,brainimagingstudieshaveshownthatthesepeoplewithbetterabilitytofinddirectionshavemoreactivehippocampuswhenlookingfordirections.
Londontaxidriversmustremembermanyplacesandknowthemostdirectroutebetweentheseplaces(theymustpassarigoroustestcalled"Knowledge"andtheEnglishnameisTheKnowledge.Togetthedriver’slicenseofLondon’sfamousblackcabblackcab).AstudyatUniversityCollegeLondon(Macguireetal,2000)showsthatcomparedtothegeneralpublic,thehippocampusofLondontaxidriversislarger,andthehippocampusofmoreexperiencedtaxidriversislarger.However,whetherhavingalargerhippocampushelpstobecomeataxidriver,orwhetherbecomingataxidriverortakingshortcutsforalivingcanmakeaperson'shippocampuslargerremainstobestudied.
ThemouseexperimentconductedatIndianaUniversityraisedthefollowingpossibility:Observingtheperformanceofmiceinrepeatedmazeexperiments,thehippocampusshapeiscloselyrelatedtothe"dimorphism".Malemicearebetteratspatializinglocationsandfindingoutwheretheyare,becausemalemicehavealargerhippocampus.
Researchresults
Thehippocampusisthepartofthebrain(cerebralcortex)inthecentralnervoussystemofmammalsthathasbeenstudiedindetail.Inanatomyandhistology,thehippocampushasaclearstructureataglance.Insidethehippocampustherearelayersthatformabeautifulappearance.Thatis,thecellbodyofthenervecellanditsneuralnetworkareaarearrangedinlayers.
Thehippocampusisapartofthelimbicsystemcalledthehippocampalregion.Thehippocampuscanbedividedinto:dentategyrus,hippocampus,subiculum,presubiculum,parasubiculum,andenterorhinalcortex.Amongthem,thecelllayersofthedentategyrus,hippocampus,andsubspindleareasinglelayer,collectivelycalledthe"hippocampalformation",whichissandwichedbetweenalow-celldensitylayerandacell-freelayer.Theotherpartsarecomposedofmultiplelayers.Thesingle-layerstructureofthedentategyrusandhippocampushascontributedtotheadvancementofneuroanatomyandelectrophysiology.
Atthebeginningofthe20thcentury,scientistsbegantorealizethatthehippocampusplaysabasicroleincertainmemoryandlearning.Especiallyin1957ScovilleandMilnerreportedaveryimportantcaseinneuropsychology.ThisisareportfromapatientcalledH.M.,whoisconsideredthemostdetailedpersoninthefieldofneuropsychology.Duetolong-termepilepsysymptoms,thedoctordecidedtoperformsurgeryforhim,removingpartofthelimbicsystemtissueunderthetemporalcortex,includingthehippocampusonbothsides.Aftertheoperation,thesymptomsofepilepsywereeffectivelycontrolled,butHMhaslostsincethen.Theabilitytoformnewdeclarativelong-termmemory.Thisdiscoveryhasbecomeanopportunityformanypeopletowanttounderstandthememoryandlearningmechanismofthehippocampus,andithasbecomeatrend.Nomatterinvariousfieldssuchasneuroanatomy,physiology,behavior,etc.,ithasdonethesameforthehippocampus.Extensiveresearch.Today,therelationshipbetweenthehippocampusandmemoryiswellunderstood.
Manypeoplearealsoveryinterestedintherelationshipbetweenhippocampusandseizures.Thehippocampusisapartofthebrainwheretheseizurethresholdislow.Becausealmostallseizuresinpatientswithepilepsystartfromthehippocampus,therearemanycaseswhereitisdifficulttotreatwithdrugslikethiskindofseizuresdominatedbythehippocampus.Moreover,apartofthehippocampus,especiallytheentorhinalcortex,isthefirstplacewhereAlzheimer'sdiseasedevelops.Thehippocampusalsoshowsthatitiseasytobeinjuredbyanemiaandhypoxia.
Thehippocampusisaresearchsampleofothercerebralcorticalsystemsinanatomy,anatomyandfunctionalstructure.Thecerebralcortexhasrecentlybeguntoreceiveattentionandresearch,andtheknowninsightsonthesynapticconductionofthecentralnervoussystemmostlybenefitfromtheresearchinthehippocampus.Therelatedknowledgeofthehippocampusismostlyderivedfromspecimensofthedentategyrusandhippocampus.
Maleandfemalehippocampus
Theso-calledsexualdimorphismreferstotheexistenceofphenotypic(physicalappearanceorcomposition)ofbothsexesofthesameorganismThedifference.Themostobviousfeatureofbisexualheterogeneityisthedifferenceinthegenitaliaofthetwosexes.Ofcourse,thisallogeneicwillalsoshowotherdifferences.
Forexample,themalesofmanyanimalshavemorevividappearancesthantheirfemalemates.Inaddition,hermaphroditismcanalsomanifestinsomedeeperandmoresubtleplaces,suchasthehumanbrainmechanism.
Studieshaveshownthatthebrainsofadultmenareabout14%largerthanthoseofadultwomen,andcontainahigherpercentageofgraymatter.——Graymatteriswhite-to-graymatter.Itexistsinthehumanbrainandspinalcord.Itisanimportantcomponentofthecentralnervoussystem.Itisdividedintograymatterandwhitematter.Therearealsodifferencesinthebody(hippocampus,theareaofthebrainthatismainlyresponsibleforlearningandmemory,andiscloselyrelatedtomemory,pressureregulation,andspatialnavigation),whichaffectsthedifferentbonestructuresofmenandwomenandthecontinuousenhancementofstructuralconnectionsbetweennervecells(neurons)(Synaptic)capabilities.
ResearchersfromtheRosalindFranklinUniversityofMedicineandScienceanalyzed76papersusingmagneticresonanceimaging(MRI,anon-invasivedetectionmethod).Researchonhumanbodystructurewithoutharmingthecomplexstructureofthehumanbody)technologyresearchpapersondifferentmaleandfemalehippocampus,andcomparetheconclusionsofthesepapers.
Itwasfoundthatthesepapersinvolvedthehippocampalvolume(HCV)ofmorethan6000menandwomenofdifferentages.Aftercomparison,therewasnosignificantdifferenceinthevolumeofthesehippocampus.
Thisresearchoverturnsthepreviousviewthatthefemalehippocampusismuchlargerthanthemale.Researchershavelongbelievedthatwomenarebetteratexpressingandmenarebetteratrationalthinkingbecauseofthedifferenceinthesizeofthehippocampusintheirbrains,butthisnewdiscoveryhasforcedresearcherstofindanotheranswerforthesedifferences.
LiseElio,aneuroscientistatRosalindFranklinUniversityofMedicalSciences,said:“Forresearchers,thebraindifferencesbetweenmenandwomenareanimportantbasisforexplainingthedifferencesbetweenmenandwomen.Butbasedonasmallnumberofdatasamples,oftenItwillmakeresearchtendtofindlargedifferencesbetweenmenandwomen;onlywhentheresearcherscollectenoughdiversedata,theresearchresultswillshowthatthedifferencebetweenthemaleandfemalebrainsisactuallyinsignificant."
Thehippocampusshrinks
AccordingtotheSydneyMorningHeraldreportonJune30,thelatestresearchshowsthatforpatientswithrecurrentdepression,theirbrainsareresponsibleformemoryandThepartthatcontrolsemotionswillshrinkduetodepression.
ProfessorIanHickieoftheBrainandMindResearchInstituteattheUniversityofSydneysaidthisdiscoveryemphasizesthetimelyidentificationandtreatmentofdepressionwhenitfirstappearsThenecessityoftreatment,especiallyforyoungpatients.Atthesametime,healsosaidthatthiskindofbrainatrophyisreversible.
Theresearchteaminvestigated1,728depressionpatientsand7,199non-patients,andanalyzedtheirbrainscansandmedicaldata.Amongthesedepressionpatients,65%sufferfromrecurrentdepression.
Researchandanalysisfoundthatthehippocampusinthebrainsofpatientswithrecurrentandpersistentdepressionissignificantlysmaller,andthehippocampusismainlyresponsibleformemoryandemotionalcontrol.ProfessorHejisaid,"Butwedidnotfindthispartofthechangeintheinitialstageofdepression,whichmeansthatthediseaseitselfcausedthischangeinthebrain.""Inthiscase,thesizeisrelated—-Ifthispartofyourbrainshrinks,thenyourmemoryandemotionalcontrolcapabilitiesarealsoweakened."Hesaid.
However,ProfessorHekialsopointedoutthatthischangeisreversible,becausethisreductionismainlyduetothedisconnectionbetweencells,ratherthanthedeathofnervecellslikedementia.Itwillgrowagainundertherightenvironment."Hesaidthatinordertopromoteregrowth,patientsshouldbetreatedwithcontinuousandeffectivetreatment,includingacombinationofpsychologicalanddrugtreatments.
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