Physiology of L- and M-cone inputs to H1 horizontal cells in the primate retina

Abstract

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.

L and M Cone Contributions to the Midget and Parasol Ganglion Cell Receptive Fields of Macaque Monkey Retina

“…H1 horizontal cells, midget ganglion cells, and parasol ganglion cells were recorded in an in vitro preparation of intact primate (Macaca nemestrina, Macaca fascicularis, Papio c. anubis) retina using methods described in detail elsewhere (Dacey et al, 2000b). Retinas were obtained through the Tissue Distribution Program at the Regional Primate Research Center at the University of Washington.…”

“…Verweij et al (2003) showed that the receptive fields of individual cone photoreceptors have surrounds that get mixed L and M cone input. H1 horizontal cells, thought to contribute to the inhibitory surrounds of midget bipolar and ganglion cells, get nonselective input from L and M cones (Wässle et al, 1989;Dacheux and Raviola, 1990;Goodchild et al, 1996;Dacey et al, 1996Dacey et al, , 2000b. There is no evidence that midget bipolar cells, which are the middle elements in the private line connections from cones to midget ganglion cells, have selective surround circuitry.…”

“…We measured responses to stimuli that systematically varied in L and M cone contrast and evaluated the relative sign and strength of L and M cone input to the receptive field (Dacey et al, 2000b). In many cases, we recorded from midget and parasol cells sequentially at the same retinal location.…”

“…Finally, we compared the relative strengths of L and M cone inputs to ganglion cells to the inputs to H1 horizontal cells, whose dendrites sum input from L and M cones (Dacey et al, 1996). The relative strengths of L and M cone input to H1 cells also varied from cell to cell (Dacey et al, 2000b) but were highly correlated with the inputs to ganglion cells at the same retinal locations. The simplest explanation for these results is that, for both the midget and parasol cells of inner retina and the H1 horizontal cells of outer retina, responses reflect the local ratio of L and M cones in the photoreceptor mosaic unmodified by cone type-selective circuitry.…”

Functional polarity of dendrites and axons of primate A1 amacrine cells

“…Tissue was prepared as previously described (Dacey et al, 2000b). In brief, Macaca nemestrina or fascicularis retinas were obtained from the tissue distribution program of the Washington National Primate Research Center at the University of Washington.…”