THE ARRANGEMENT OF L AND M CONES IN HUMAN AND A PRIMATE RETINA

摘要: The relative numerosities and the spatial arrangement of long-wave (L) middle-wave (M) cones in human primate retina have long been debated. This topographical organization is fundamental to our understanding visual sensitivity colour vision. To date, owing very similar structure L M opsins (Nathans et al. 1986), it has not possible label two spectral classes cone independently, thus indirect methods had be employed. In humans, psychophysical estimates (Vos Walraven 1971; Cicerone Nerger 1989; Pokorny e t 1991) suggested a preponderance cones, with an average : ratio close 2 1, but considerable variation between individuals, estimated ratios ranging from about 0.3 1 3 (Rushton Baker 1964). More recent findings, including ERG measurements (Carroll 2000; Dobkins 2000), suggest confirm individual variability, as high 12 1. Adaptive optics made direct imaging photoreceptor mosaic for spatially localized retina1 densitometry allowed by differential bleaching (Roorda Williams 1999; Brainard Roorda 2001). For individuals this method gave 1.2 3.8 distribution appeared random. Estimates also levels mRNA, either whole or regionally located pieces retina. retinae appears increase central periphery, fovea 1.3: rising 3.5 5 mid periphery (Yamaguchi 1997; Hagstrom 1998,2000). There was individuals. suggestion that number increases towards (Hagstrom 1998) implies cone-rich rim at ora serrata may dominated cones. stochastic process thought determine which form longor opsin will expressed given cone. genes are