Introduction
Ganglioncelllayer:Locatedintheinnermostlayeroftheretina,itiscomposedofmultipolarganglioncells.Itsdendritesaremainlyconnectedwithbipolarcellsandcanalsopassthroughapodocytes.Lateralconnection;itsaxonsextendtotheopticnerveheadandpassthroughthelaminatoformtheopticnerve.
Transmittingsignals
Thereareseveraldifferenttypesofganglioncellsthattransmitbrightnesssignals,andtheyareexcitedbybipolarcells,horizontalcells,andapodocytesindifferentsituations.Asmallnumberofganglioncellsmainlyrespondtotheintensity(brightness)ofthelightthathitsthephotoreceptors.Aslongasthebrightnessishigh,thefrequencyofimpulsesfromthesecellsisalwayshigherthanthenaturalfrequencyoffiringimpulses.Itisthesignalsemittedbythesecellsthatletthebrainknowthetotalbrightnessofthesceneitsees.
Transmitthesignalaboutthecontrastinthevisualscene-intheprocessoflateralinhibition,mostganglioncellshardlyrespondtotheactuallevelofbrightnessinthescene,butonlyreacttotheedgeofthecontrastinthescene.Becausethisisthemainwaytheformofthesceneistransmittedtothebrain,thefollowingexplainshowthisprocessoccurs.
Whenuniformlighthitstheentireretina(thatis,whenallphotoreceptorsareequallyexcitedbytheincidentlight),thecontrasttypeganglioncellsareneitherexcitednorinhibited.Thisisbecausethesignalstransmitteddirectlyfromthephotoreceptorsthroughthebipolarcellsareexcitatory,whilethesignalstransmittedfromthesurroundingphotoreceptorsthroughthehorizontalcellsareinhibited.Thesetworeactionsoffseteachother.Onthecontrary,ifthereisacontrastedge,thephotoreceptorsononesideoftheedgeareexcited,andthephotoreceptorsontheothersideoftheedgearenotexcited,thereisnodirectoffsetbytheexcitatorysignalofthebipolarcellandthehorizontalcellinhibitorysignal.Theresultisthattheganglioncellsonthebrightsideareexcited,whilethedarksideissuppressed.
Thebalanceprocessoftheexcitatorysignalandtheinhibitorysignalisexactlythesameasthelateralinhibitionduringthetransmissionofvariousothersensorysignals.Thisprocessisamechanismusedbythenervoussystemtoenhancecontrast.
Přijímací pole
Dva typy gangliových buněk: ON-centredtype,OFF-centredtype
Typ ON-centred
Když se světlo objeví ve středu vnímavého pole, střelba této buňky ganglionu se náhle zvýší. (Distribuovaná oblast je kruh se středem pole pohledu jako bod. Tato oblast se nazývá oblast ON); světelný bod, který se používá k jeho stimulaci, dojde k opačnému efektu. Pokud světelný bod dopadne zcela do jiné oblasti, emise na pozadí se zcela zastaví. Tato oblast se nazývá oblast VYPNUTO. [ON])“. U centrovaných gangliových článků ON je světelná energie dopadající (dávat) v oblasti ON Viz, světlo dopadající (dávat) v zóně OFF není vidět.
OFF-centeredtype
Whenthelightspotisremovedfromthecenterofthereceptivefield,itwillemitstrongly.(ThesmallcircularareaemittedistheONarea).Onthecontrary,ifthelightisinthecenterofthefieldofview,itstopsemitting.Outsidethissmallcentralcirculararea,thereisanannularrangearoundthem.Inthisring-shapedarea,ifthesmalllightspotisremoved,thedistributionwillstop.ThisareaiscalledtheOFFarea.Fromthispointofview,OFF-centeredcellsbelongtothe“light-extractedtype(thelightspotinthecenterofthefieldofviewisremovedtoproduceemission,andthelightwillstopemitting[OFF])".ForOFF-centeredganglioncells,ThelightevacuatedintheONareacanbeseen,andthelightevacuatedintheOFFareaisinvisible.Inthesameway,thelightfallingintheONareaisinvisible,andthelightfallingintheOFFareacanbeseen.
Visualreceptivefieldreferstoacertainareaorrangeontheomentum.Whenitisstimulated,itcanactivatetheactivityoftheinterlayernervecellsthatareconnectedtothevisualsystemandthisarea.Thisareaontheomentumisthereceptivefieldofthesenervecells.Thereceptivefieldofaganglioncellisonlyintheareaconnectedtoitontheretina.Towhatextentanervenodeisconnectedtotheretina,thelargestreceptivefieldisthesize.