Color Vision

Color+Vision%0d%0aBy+Andrew+J+Pakchoian+Psych+159+Prof+Macleod%0d%0a%0d%0a%0cRoad+Map%0d%0a%e2%80%a2+Pigment+anatomy+%e2%80%a2+Photoreceptor%0d%0a%0d%0aanatomy+%e2%80%a2+Neurobiology+of+color+vision+%e2%80%a2+Physiology+of+color+blindness%0d%0a%0d%0a%0cKey+Terms%0d%0a%e2%80%a2+MC+layer+magnocellular+%e2%80%a2+PC+layer+parvocellular+%e2%80%a2+LGN+lateral+geniculate+nucleus%0d%0a%0d%0a%0cPigment+Anatomy%0d%0a%e2%80%a2+3+types+of+cones%3a%0d%0a%0d%0a%e2%80%a2+%e2%80%a2+%e2%80%a2%0d%0a%0d%0ashort+(S)%2c+middle+(M)%2c+and+long+(L)+wavelength+sensitive.+(S)%3a+430+nm+%3d+blue+(M)%3a+530+nm+%3d+green+(L)%3a+560+nm+%3d+red%0d%0a%0d%0a%0cPigment+Anatomy%0d%0a%e2%80%a2+Origin+of+pigments%0d%0a%e2%80%93+Red%2fgreen+from+opsin+gene+on+X-chromosome+or+sex+chromosome.+%e2%80%93+Show+very+similar+amino+acid+seqs.+(96%25)+%e2%80%93+Blue+on+chromosome+7+and+rhodopsin+on+chromosome+3+are+very+different.%0d%0a%0d%0a%0cPhotoreceptor+Anatomy%0d%0a%e2%80%a2+Cones+more+concentrated%0d%0anear+fovea%0d%0a%e2%80%93+Adapts+to+a+wide+range+of+illumination+colors+and+levels.%0d%0a%0d%0a%e2%80%a2+Rods+spread+throughout%0d%0athe+retina%0d%0a%e2%80%93+Provide+quick+response+to+changes+in+illumination.%0d%0a%0d%0a%0cPhotoreceptor+Anatomy%0d%0a%e2%80%a2+Measuring+Wavelengths%3a%0d%0a%e2%80%93+Short+wavelengths+causes+the+green+receptor+to+fire.+%e2%80%93+As+the+wavelength+gets+longer+and+closer+to+580+nm+the+red+begins+to+fire%2c+surpassing+the+green.+%e2%80%93+Get+mix+of+wavelengths.%0d%0a%0d%0a%e2%80%a2+Therefore%2c+color+vision+is%0d%0a%0d%0athe+consequence+of+unequal+stimulation+of+the+3+types+of+cones.+In+a+specific+ratio.%0d%0a%0d%0a%0cPhotoreceptor+Anatomy%0d%0a%e2%80%a2+Example%3a+if+you%0d%0astimulate+all+3+types+of+cones+about+equally+the+result+is+white+or+no+color.%0d%0a%0d%0a%0cNeurobiology+of+color+vision%0d%0a%e2%80%a2+Once+again+3+types+of+cones%3a%0d%0aS%2c+M%2c+and+L.+%e2%80%a2+Only+2+types+of+horizontal+cells%3a%0d%0a%0d%0a%e2%80%93+H1+which+connects+L+and+M+cells.+%e2%80%93+H2+which+connects+S+with+some+L+and+M+cells.%0d%0a%0d%0a%e2%80%a2+The+relation+between+high%0d%0a%0d%0aspecificity+of+cone+connectivity+and+chromatic+processing+is+unclear.%0d%0a%0d%0a%0cNeurobiology+of+color+vision%0d%0a%e2%80%a2+Blue%2fYellow+Pathway%3a%0d%0a%e2%80%93+2+Systems%3a%0d%0a%0d%0a%e2%80%a2+Differentiate+signal+from+S%0d%0a%e2%80%a2+%e2%80%a2+%e2%80%a2%0d%0a%0d%0aand+the+summed+signal+from+L+and+M.+%3d+%2bS-(L%2bM)+Receives+input+from+S-cone+bipolars+(ON)+and+L+and+M+cone+bipolars+(OFF)+Second+system+%3d+-S%2b(L%2bM)+Input+signals+are+unclear.%0d%0a%0d%0a%e2%80%93+Conclusion%3a+The+ganglion+cells+%3a+Small+bistratified+cell+and+small+bodied+inner+cell+form+blue%2fyellow+pathway.%0d%0a%0d%0a%0cNeurobiology+of+color+vision%0d%0a%e2%80%a2+Red%2fGreen+Pathway%3a%0d%0a%e2%80%93+Differentiate+between+signals+from+the+L+and+M+cones.+%e2%80%93+Path%3a+Single+L+and+M+cones+receive+input+connect+to+single+midget+bipolar+cells+contact+single+midget+ganglion+cells+project+to+the+PC+layer+of+LGN.%0d%0a%0d%0a%0cNeurobiology+of+color+vision%0d%0a%e2%80%a2+Red%2fGreen+Pathway+Cont%e2%80%99d%3a%0d%0a%e2%80%a2+L+and+M+cones+have+two+forms%3a+ON%0d%0a%e2%80%a2%0d%0aand+OFF-centre+ON-center+midget+cells+for+L+and+M+have+identical+arrays+and+same+with+the+OFF-center+There+is+no+overlap+between+dendritic+trees+of+central+midget+ganglion+cells+which+leads+to+the+exact+1%3a1+ratio+of+cones+to+ganglion+cells.+More+than+10+to+15+degrees+in+the+periphery+we+do+find+some+overlap+of+dendritic+trees+in+the+midget+bipolar+cells%2c+but+not+ganglion.%0d%0a%0d%0a%e2%80%a2%0d%0a%0d%0a%e2%80%a2%0d%0a%0d%0a%0cNeurobiology+of+color+vision%0d%0a%e2%80%a2+Interesting+facts%3a%0d%0a%e2%80%93+In+the+periphery+of+the+retina+chromatic+sensitivity+drastically+decreases%2c+but+responsiveness+of+PC+cells+is+unchanged+Connectivity+to+midget+bipolar+cells+is+not+random.%0d%0a%0d%0a%0cPhysiology+of+color+blindness%0d%0a%e2%80%a2+Male+dominant+trait+but+females+%e2%80%a2%0d%0a%0d%0a%e2%80%a2%0d%0a%e2%80%a2+%e2%80%a2+%e2%80%a2+%e2%80%a2%0d%0a%0d%0acarry+it.+Females+have+2+X+chromosomes+so+trait+is+normally+not+expressed.+Males+have+1+X+and+1+Y+chromosome+which+means+recessive+traits+will+show+in+phenotype.+As+stated+before%2c+red+and+green+pigments+originate+on+the+X+chromosome.+1+in+20+males+suffers+from+some+form+of+color+blindness.+Most+common+is+red-green+color+blindness+which+is+caused+by+problem+with+M+or+L+cones.+However%2c+they+can+still+see+red+and+green%2c+but+have+trouble+with+light+or+desaturated+colors.%0d%0a%0d%0a%0cPhysiology+of+color+blindness%0d%0a%e2%80%a2+A+few+types%3a%0d%0a%e2%80%93+Anomalous+Trichromacy%3a+have+3+photopigments%2c+but+only+from+2+groups.+%e2%80%a2+Most+common+is%0d%0adeuteranomalous+%3d+2+L+photopigments.%0d%0a%0d%0a%e2%80%93+Dichromacy%3a+missing+1+group+of+photopigments.%0d%0a%0d%0a%0cWhich+picture+contains+a+red+crayon%3f%0d%0a%0d%0a%0cExample%0d%0a%0d%0a%0c%0cQuiz%0d%0aTrue+or+false%3a+The+dendritic+trees+of+midget+ganglion+cells+overlap.%0d%0a%0d%0a%0cAnswer%0d%0aFalse%0d%0a%0d%0a%0cReferences%0d%0a%e2%80%a2+Colorblindness%3a+%e2%80%a2+%e2%80%a2+%e2%80%a2+%e2%80%a2+%e2%80%a2%0d%0ahttp%3a%2f%2fsrv2.lycoming.edu%2f%7enewman%2fcourses%2fbio22298%2fdisorderpapers%2fColorbli+ndness%2fpreliminary.htm+Hubel%2c+David+H.+Eye%2c+Brain%2c+and+Vision.+Harvard+Medical+School.+15+Jan.+2005+Lee%2c+Barry+B.+%22Paths+to+Colour+in+the+Retina.%22+Rev.+of+Current+understanding+of+neurobiology+of+color+vision.+Clinical+and+Experimental+Optometry+20+June+2004%3a+239-248.+Levine%2c+Michael+W.+Fundamentals+of+Sensation+and+Perception.+3rd+ed.+New+York%3a+Oxford%2c+2000.+94-110.+Neitz%2c+Jay+%2c+and+Maureen+Neitz.+Neitz+Color+Vision+Lab.+21+Feb.+2002.+Dept.+of+Opthamology%2c+Medical+College+of+Wisconsin.+14+Jan.+2005.+Scott%2c+Ed.+Spectral+Selectivity.+1997.+Luminal+Path+Corporation+and+contributors.+15+Jan.+2005.%0d%0a%0d%0a%0c