Accueil Technologie Centre visuel

Centre visuel



Courte introduction

Concept

Vision centrale isthenervecellinthecerebralcortexthatisinvolvedintheformationofvisiongroup.Itislocatedontheoccipitalcortexonbothsidesofthetalarfissure, thatis, theuppercuneiformgyrusandthelowerlingualgyrus.Becauseofthespecialstructureofthecortex, therearewhitefinelinesonthecrosssection, soitisalsocalledthestriatedarea.Thevisualcenterofeachhemisphereisrelatedtohalfofthevisualfieldofbotheyes, sototalblindnessoccurswhenthevisualcentersofbothhemispheresarecompletelydamaged.

Emplacement du cerveau

Thevisualareaof thehumancerebralcortexislocatedintheoccipitallobe (area17) .Theleftoccipitalcortexreceivesafferentnerveprojectionsfromthetemporalretinaofthelefteyeandthenasalretinaoftherighteye.Therightoccipitalcortexreceivesafferentfiberprojectionsfromthetemporalretinaoftherighteyeandthenasalretinaofthelefteye.Theupperhalfoftheretina (thelowerquadrantofthefieldofview) isprojectedtotheupperedgeofthetalariacleft; thelowerhalf (theupperquadrantofthefieldofview) isprojectedtotheloweredgeofthetalariscleft.Therefore, damagetotheloweredgeofthetalusfissurewillappearasadefectintheupperquadrantintermsofhumanvision.Themacularareainthecenteroftheretinaisprojectedtothebackofthetaluscleft, andthemarginalareaisprojectedtothefrontofthetaluscleft.Therepresentativeareaof themaculaisrelativelylargerinboththecortexandthelateralgeniculatebodythantheborderrepresentativearea.

Le mécanisme central de formation de la vision

Le processus de formation de la vision

Cellsareexcited, andthecellsattheleveloftheretinaarecomposedandanalyzedinaloop.Thex, Y, andWneuronsparticipateinthecontrast, orientation, distanceandothermechanismsofthesurfaceoftheextractedobject.Differentneuronshavedifferentorientations, differentspatialfrequencies, andimages.TheresponseofthevisualsystemisbasedontheperformanceoftheFourieralgorithm, andthenthevisualsystemextractsprimitiveprimitivesfromtheretinalscenetoperformsymbolgroupoperations.Inthisway, visualinformationpassesthroughvisualcells, bipolarcells, horizontalcells, andganglioncells, andpassesthroughtheopticnerve.The forme « en série » informationpatternistransmittedtothelateralgeniculatebodytobedecodedintoa « treillis », andthentransmittedbyopticradiationtodifferentfunctionalareasoftheprimaryvisualcortex, andfinallytransmittedtothecorrespondingdivisionoflaborareasofthehigh- zone de niveau, et intégrée dans différentes zones corticales pour produire une connaissance complète de l'information visuelle.

La voie centrale de vision et de positionnement cortical

Thevisualpathwayconsistsoffourlevelsofneurons, Thefirst, deuxième, andthirdlevelsofneuronsarelocatedintheretina, andthefourthlevelofneuronsislocatedontheoutsideThegeniculatebody, fromwhichthenervefibersarefinallyterminatedintheopticcenterofthecerebralcortex.Theopticnerve, whichiscomposedofaxonsofthird-levelneurons (ganglioncells), entersthecranialcavityafterleavingtheeyeball.Itmergesintotheopticchiasmatthebottomofthethirdventricle, wherehalfofthefiberscrosstotheoppositeside.Theruleisthatthefibersfromthenasalretinaofbotheyes (thatis, thepartthatreceiveslightstimulationfromthetemporalside) crosstothecontralateralsideandascendtothecontralaterallateralgeniculatebody.Thefibersfromthetemporalretina (thatis, thepartthatreceiveslightstimulationfromthenasalside) donotcross, andascendtotheipsilaterallateralgeniculatebody.Inthisway, theleftandrighthalvesoftheentirefieldofviewareprojectedtotheoppositecerebralhemispheres.Theopticnervefibersformtheleftandrightoptictractsafterpassingthroughtheopticchiasm , et certains d'entre eux eachthesuperiorcolliculusofthequadruplex, andparticipateinactivitiessuchasvisualaccommodationreflex, lightreflex, andvisualmotorreflex; mostofthefibersstopatthelateralgeniculatebody.Theinternalstructureofthelateralgeniculatebodyiscomposedof6layersofnervecells, andthepartsrelatedtocentralvisionandperipheralvisioncanbeclearlydistinguished.Theopticnervefibersfromtheintersectioncorrespondingtothefoveaterminateinlayers1,4, et6, andthenon-intersectingopticnervefibersterminateinlayers2,3, and5.Thoseequivalenttothenear-peripheralareastopat1,6,2, and3layersrespectively, andthoseinthefar-peripheralareastopatlayers1,2respectively.Theendofeachopticnervefiberisdividedinto5-6smallbranches, eachofwhichterminatesinacellbodyofthelateralgeniculatebody, plutôt que lesendrites.Par conséquent,chaquefoisunefibrenerveuxoptiqueestendommagé,ilestpossiblededégénérerlescellulesdanslescouches2,3,et5surlecôtéipsilatérauxoulescouches1,4,et6surlecôtécontralatéral. daunestationrelaisentrelecortexcérébraletlarétine.

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