Retinal pathways for colour vision: Studies of short-wavelength sensitive ("blue") cones and their connections in primate retina

Colour vision depends on the presence of photo-receptors with distinct spec tral sensitivity and on post-receptoral mechanisms which can compare the re lative activation of these receptors. We review recent work on the retinal pathways for colour vision in primates, with emphasis on the cells and path ways involved with processing signals from short-wavelength sensitive (SWS or "blue") cones. We find that there is substantial variability in the dist ribution of SWS cones when the retinae of different primate species are com pared Despite these differences, the synaptic connectivity of SWS cones is very similar in all primates studied so far, The SWS cones are contacted se lectively by a depolarising (On-) bipolar cell type, and are biased in thei r connectivity towards one subset (H2) of horizontal cells. A distinct clas s of retinal ganglion cell is responsible for transmitting "blue-yellow" co ne opponent signals to the brain. The intra-retinal pathways for SWS cone s ignals are indistinguishable in dichromatic and trichromatic monkeys, sugge sting that the SWS chromatic subsystem is an ancient and well-preserved fea ture in the retina of diurnal primates. (C) 2000 John Wiley & Sons, Inc. Co l Res Appl, 26, S112-S117, 2001.