Receptive field properties of the photopic luminosity horizontal cell of carp retina.

The receptive field of the LEHC of the carp's retina is different when tested with red versus green stimuli. The sensitivities to 706 nm vs 519 nm flashes were compared for various size spots centered on the receptive field. Full summation (area times intensity equaling a constant at threshold) and greater than full summation were found to occur up to larger diameters of spots with red illumination than with green. A further test was made of the effect of constant background green (502 nm) illumination on the sensitivity to red vs green flashes. At all background intensities the sensitivity to red vs green flashes. At all background intensities the sensitivity to green flashes was reduced, but over an optimal range of background intensities the sensitivity to red flashes was increased. These findings are explained in terms of a previously proposed model of cone-LEHC connections.