Latencies and discharge patterns of color-opponent neurons in the rainbow trout optic tectum

Although color-opponent neurons appear to subserve color vision, precisely how these cells encode hue is still not clear. Single-unit, extracellular r ecordings from the rainbow trout optic tectum were made in order to examine the possible role of action potential timing in coding chromatic stimuli. We found that color-opponent units can exhibit differences in response late ncy which are a function of wavelength and response sign, with the OFF resp onse exhibiting the shorter response latency. We also found that units ofte n responded with spike bursts characterized by early and late spikes separa ted by a silent period, with the relative proportion of early and late spik es varying as a function of wavelength. This type of discharge pattern appe ars to be a result of inhibitory, color-opponent processes. We suggest that complete inhibition of early spikes may be the mechanism underlying the ob served latency differences. These findings suggest a role for action potent ial patterning in coding chromatic stimuli. (C) 1999 Elsevier Science Ltd. All rights reserved.