Vision-Florida-Atlantic-University視覺-佛羅里達大西洋大學共4課件

Vision-FloridaAtlanticUniversity視覺-佛羅里達大西洋大學56、死去何所道，托體同山阿。57、春秋多佳日，登高賦新詩。58、種豆南山下，草盛豆苗稀。晨興理荒穢，帶月荷鋤歸。道狹草木長，夕露沾我衣。衣沾不足惜，但使愿無違。59、相見無雜言，但道桑麻長。60、迢迢新秋夕，亭亭月將圓。Vision-FloridaAtlanticUniversity視覺-佛羅里達大西洋大學Vision-FloridaAtlanticUniversity視覺-佛羅里達大西洋大學56、死去何所道，托體同山阿。57、春秋多佳日，登高賦新詩。58、種豆南山下，草盛豆苗稀。晨興理荒穢，帶月荷鋤歸。道狹草木長，夕露沾我衣。衣沾不足惜，但使愿無違。59、相見無雜言，但道桑麻長。60、迢迢新秋夕，亭亭月將圓。6:VisionBiologicalBasesofBehaviorSensorySystemsThebraindetectseventsintheexternalenvironmentanddirectsthecontractionsofthemusclesAfferentneuronscarrysensorymessagestobrainEfferentneuronscarrymotormessagestothemusclesStimulus:anyenergycapableofexcitingareceptorMechanicalChemicalThermalPhotonicSensoryenergiesaremeasurable(unlikeESP)6.36:VisionBiologicalBasesofBehaviorSensorySystemsThebraindetectseventsintheexternalenvironmentanddirectsthecontractionsofthemusclesAfferentneuronscarrysensorymessagestobrainEfferentneuronscarrymotormessagestothemusclesStimulus:anyenergycapableofexcitingareceptorMechanicalChemicalThermalPhotonicSensoryenergiesaremeasurable(unlikeESP)6.3SensoryReceptorsReceptorsare

specializednervecellsthattransduceenergyintoneuralsignalsReceptorslackaxons,formsynapseswithdendritesofothersensoryneuronsReceptorsare“mode”specific“LawofSpecificNerveEnergies”:sensorymessagesarecarriedonseparatechannelstodifferentareasofthebrainReceptorsdetectasmallrangeofenergylevelsEye:400-700nMEar:20-20,000HzTastebuds:specificchemicals6.4VisualSystemsThefunctionofavisualsystemistodetectelectromagneticradiation(EMR)emittedbyobjectsHumanscandetectlightwithawavelengthbetween400-700nMPerceivedcolor(hue)isrelatedtothewavelengthoflightBrightnessisrelatedtotheintensityoftheradiationFunctionsofvisionDiscriminatefigurefrombackground(foodorrock?)Detectmovement(predator/prey?)Detectcolor(adaptivevalueofcolorvision)6.5EyeDetailsAneyeconsistsof:Aperture(pinhole,pit,orpupil)toadmitlightLensthatfocuseslightPhotoreceptiveelements(retina)thattransducethelightstimulusSource:/nei/vision/vision2.htm6.6RetinaLightpassesthroughthepupilandisfocusedbythelensontotheretinaatthebackoftheeyeTheretinaconsistsofthreelayersofcellsGanglioncelllayerBipolarlayerPhotoreceptorlayer:receptorsinthislayertransducelightTheganglioncelllayeristheoutermostlayerandthephotoreceptorlayeristheinnermostlayerInordertoreachthephotoreceptorlayer,lightactuallypassesthroughtheoutertwolayersoftheretina6.7RodsandConesTwotypesofphotoreceptorsarelocatedwithintheretinaRods:120millionLightsensitive(notcolor)FoundinperipheryofretinaLowactivationthresholdCones:6millionArecolorsensitiveFoundmostlyinfovea

Theoutersegments(O.S.)ofarodoraconecontaindifferentphotopigmentsthatreacttolightSource:/Webvision/imageswv/rodcoEM.jpeg6.8RetinalCircuitry6.9AdaptedfromDowling,J.E.,andBoycott,B.B.ProceedingsoftheRoyalSocietyofLondon,B.,1966,166,80-111.PrimaryVisualPathwayInformationfromeachvisualfieldcrossesoverattheopticchiasmandprojectstotheoppositesideoftheprimaryvisualcortex6.10VisualPathways:LGNSignalsfromtheganglioncellsoftheretinaaresenttothethalamusviatheopticnerve/tractThedorsallateralthalamicnucleus(LGN)has6layersEachlayerreceivesinputfromonlyoneeyeTheinner2layerscontainlargecells(magnocellular)Theouter4layerscontainsmallcells(parvocellular)Koniocellularsublayersareventraltoeachofthe6layersNeuronsoftheLGNprojectthroughtheopticradiationstoaregionofoccipitalcortextermedprimaryvisualcortex(striate)6.11VisualPathways:LGN6.12OverviewoftheVisualCortexHumanvisualareasV1V2V3V3AV4PosteriorAnteriorcm6.13Visualareasoccipitallobes,posteriorviewV1V2V3V3aV4vMT+leftrightcmOrganizationofV180UpperVMLowerVMHM6.15VisualTransductionPhotopigmentsarelocatedinthemembraneoftheoutersegmentofrodsandconesEachpigmentconsistsofanopsin(aprotein)andretinal(alipid)Inthedark,membraneNA+channelsareopen->glutamateisreleasedwhichdepolarizesthemembraneLightsplitstheopsinandretinalapart->Activatestransducin(Gprotein)->Activatesphosphodiesterase->ReducescGMP->closesNA+channelsTheneteffectoflightistohyperpolarizetheretinalreceptorandreducethereleaseofglutamate6.16RetinalResponsestoLight6.17ReceptiveFieldsMicroelectrodescanbeusedtorecordthefiringactivityofasinglesensoryneuronSensoryneuronshaveabackgroundrateoffiring(impulses/sec)ThisrateoffiringcanincreaseordecreaseinresponsetoastimulusReceptiveField(RF):ThoseattributesofastimulusthatwillalterthefiringrateofsensorycellThegeneralpatternoftheRFcanberecordedateachlevelofasensorysystem(e.g.fromaperipheralsensoryreceptor,thethalamus,orthecortex)RFanalysescanindicatethemannerinwhichsensoryinformationconvergesfromleveltolevel6.18GanglionCellReceptiveFieldsGanglioncellsintheretinalperipheryreceiveinputfrommanyphotoreceptorswhileganglioncellsinthefoveareceiveinputfromonephotoreceptorThereceptivefieldsofganglioncellsarecircularwithacenterfieldandasurroundfield“ON-Cell”:CellexhibitsalowbaselinefiringrateLightplacedincenterringincreasesfiringrateLightplacedonsurrounddecreasesfiringrate“OFF-Cell”LightplacedincenterringreducesfiringrateLightplacedonsurroundincreasesfiringrateONOFF6.19ColorVisionTheoriesTrichromatictheory(ThomasYoung1802)arguedthereare3differentreceptorsintheeye,witheachsensitivetoasinglehueAnycolorcouldbeaccountedforbymixing3lightsinvariousproportionsOpponenttheory(EwaldHering1905/65)notesthatpeopleperceiveopponentcolors:yellow/blueandred/greenYellowisaprimarycolorratherthanamixtureofredandblue-greenlightNegativecolorafterimagessuggestthatredandgreenarecomplementarycolorsasareblueandyellow6.20ColorVisionSystems6.21 TritanopiadeuteranopiaprotanopiaColorVisionSystemsPrimateretinacontains3typesofphotoreceptorsEachconeusesadifferentopsinwhichissensitivetoaparticularwavelength(blue,red,green),supportingtrichromatictheoryAttheganglioncelllevel,thesystemrespondsinanopponent-processfashionAgivencellmightincreaseitsfiringratetoyellowlightinthecenter,butdecreaseittobluelight6.22Center-Surround:LGN/Retina6.23VisualPathways:StriateCortexStriatecortexisorganizedinto6layersLayer4creceivesinformationfromtheparvocellularandmagnocellularlayersoftheLGNThevisualinformationisthesenttolayersaboveandbelowlayer4cforanalysisMicroelectrodereceptivefieldstudieshavesoughttoidentifythefeaturesoftheexternalworldthatactivatecellsinstriatecortexOrientationsensitivity:somecellsfirebesttoastimulusofaparticularorientationandfirelesswhenorientationisshiftedSpatialfrequency:cellsvaryfiringrateaccordingtothesinewavefrequencyofthestimulus6.24OrientationSensitivity6.25BestorientationSpatialFrequencyVisualneuronsrespondtoasinewavegrating:AlternatingpatchesoflightanddarkLowfrequency:largeareasoflightanddarkHighfrequency:finedetails6.26ModularOrganizationofStriateCortexStriatecortexisorganizedintomodules(~2500)Stainsforcytochromeoxidase(CO)revealtwo”COblobs”ineachmoduleCellswithineachCOblobaresensitivetocolorandtolowfrequencyinformationOutsideeachblob,neuronsrespondtoorientation,movement,spatialfrequencyandtexture,butnottocolorinformationStriatemodulesshowOculardominance:cellsineachhalfofthemodulerespondtoonlyoneeyeOrientationcolumns:Cellsrespondtosameorientation,adjacentcellsareshiftedby10degreesAreorganizedatrightanglestotheoculardominancecolumns6.27ModulesinVisualCortex6.28CytochromeOxidaseblobsinV1

VisualSystemDivisionsMagnocellularsystemCellsfromretinaterminateinLGNlayers1,2andthenprojecttolayer4CofstriatecortexCarryinfooncontrastandmovement(colorinsensitive)SystemisfoundinallmammalsParvocellularsystemCellsfromretinaterminateinLGNlayers3-6andthenprojecttolayer4CofstriatecortexCarryinfoonfinedetail,andcolor(red,green)SystemisfoundinprimatesKoniocellularsystemSystemprojectsfromLGNtoblobsinstriatecortexSystemcarriescolorinformation(blue)Systemisfoundonlyinprimates6.30PrimaryVisualPathway6.31GIRKINANDMILLER

SurvOphthalmol45(5)March–April2001VisualAreasinLateralandMedialViewsofOccipitalCortexVisualAssociationCortexVisualinformationistransmittedtoextrastriatecortex(termedvisualassociationcortex)viatwostreamsDorsalstream:“where”anobjectisReceivesmostlymagnocellularinputProjectstopost.parietalassociationcortexVentralstream:“what”anobjectis(analysisofform)ReceivesanequalmixofmagnocellularandparvocellularinputProjectstoextrastriatecortex(V2,V3,V4,V5)andtoinferiortemporalcortex(TEO,TE,STS)6.33VisualCortex:what/where6.34PETstudyofwhere/whatdichotomy6.35FacecellsinSTSofmacaquemonkey6.36Agnosiareferstoafailuretoperceiveoridentifyastimulusbymeansofasensor