Abstract
Despite over two hundred years of perceptual and physiological work in the study of color vision the precise manner in which signals from L, M, and S cones are combined to result in the hues we perceive is still mysterious. While it is well established that early in the visual system color information is processed in two chromatically opponent channels, the L–M and S-cone opponent channels1, it has also been established that these channels do not satisfactorily explain color perception. For example, despite the L–M and S-cone channels often being associated with red-green and blue-yellow psychophysical color opponency these so-called unique hues are not the colors that are perceived under isolated activity of the cone opponent channels2.
Our approach exploits a phenomenon described by Holmgren3, that small flashes of light appear to fluctuate in color, to probe the contributions of individual cones to hue and provide insight into the microstructure of the chromatic mechanisms. Detection and perception of near-threshold, monochromatic flashes of light, made smaller than individual cones with adaptive optics, were studied in subjects with known retinal mosaics and a wide range of L:M ratios. Our findings suggest that M cones contribute to blueness and that cones within the same class contribute differently to color perception depending on local retinal typography, with cones within clumps of like-type cones apparently failing to participate in chromatic pathways. We then discuss recent efforts to directly link elicited sensations with the individual cones responsible for detection using an ultra-high resolution retinal stimulus tracking method4.