Physiology of L- and M-cone inputs to H1 horizontal cells in the primate retina.
In the primate retina, H1 horizontal cells form an electrically coupled network and receive convergent input from long- (L-) and middle- (M-) wavelength-sensitive cones. Using an in vitro preparation of the intact retina to record the light-evoked voltage responses of H1 cells, we systematically varied the L- and M-cone stimulus contrast and measured the relative L- and M-cone input strength for 137 cells across 33 retinas from three Old World species (Macaca nemestrina, M. fascicularis, and Papio anubis). We found that the L- and the M-cone inputs were summed by the H1 cell in proportion to the stimulus cone contrast, which yielded a measure of what we term L- and M-cone contrast gain. The proportion of L-cone contrast gain was highly variable, ranging from 25% to 90% [mean +/- standard deviation, (60 +/- 14)%]. This variability was accounted for by retinal location within an individual, with the temporal retina showing a consistently higher percentage of L-cone gain, and by large overall variation across individuals, with the mean percentage of L-cone gain ranging from 32% to 80%. We hypothesize that the relative L- and M-cone contrast gain is determined simply by the relative number of L and M cones in the H1 cell's receptive field and that the variability in L- and M-cone contrast gain reflects a corresponding variability in the mosaic of L and M cones.
Dacey
D M
DM
Department of Biological Structure and the Regional Primate Research Center, University of Washington, Seattle 98195-7420, USA.
Diller
L C
LC
Verweij
J
J
Williams
D R
DR
D000818:Animals; D008027:Light; D008252:Macaca fascicularis; D008254:Macaca nemestrina; D010215:Papio; D011323:Primates / Q000502:physiology*; D012160:Retina / Q000166:cytology / Q000502:physiology*; D017949:Retinal Cone Photoreceptor Cells / Q000502:physiology* / Q000528:radiation effects