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.
Рецептивно поле
Два вида ганглийни клетки: ON-центриран тип, OFF-центриран тип
ON-центриран тип
Когато светлинни петна попаднат в центъра на възприемчивото поле, активирането на тази ганглийна клетка внезапно се засилва. (Разпределената област е кръг с точка в центъра на зрителното поле. Тази област се нарича ON-област); извън този малък център около тях има кръгова зона. llсветлинна точка, използвана за стимулирането му, ще възникне обратният ефект. Ако светлинните петна попаднат изцяло в друга област, фоновите емисии спират напълно. Тази област се нарича ИЗКЛЮЧЕНА зона. [ON])”.За ON-центрирани ганглийни клетки светлинната енергия, падаща (отдаваща) в ON-областта, е невидима.
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.