Computer Model of Color Vision Circuit Parallels Psychophysical Responses to Single Cone Photoreceptor Stimulation by a 550 nm Wavelength Light

Abstract

Adaptive optics allows for near diffraction-limited imaging of the photoreceptor mosaic in vivo. Hofer et al. (Journal of Vision 2005 (5)) used this technology, essentially in reverse, to deliver points of 550 nm light to the retina. We compared their psychophysical results to those from a computer implementation of a physiologically-based model of the circuit for color vision in which the cortex performs an operation on the LGN input analogous to that carried out by the midget ganglion-cell circuit on the cone signals. This forms cortical circuits that resolve the confound between diffuse colored lights and luminance edges without introducing cell-type specific L/M connections or Hebbian learning to inform the appropriate neural wiring. Circuits for color were imposed by the receptor mosaic and by post-receptoral elements early in the pathway as a consequence of indiscriminate comparisons of the activity of a cell with its neighbors. Retinal mosaics were created to match the L:M ratios of the subjects tested by Hofer et al. Retinal coordinates were randomly chosen for stimulation by the 550 nm stimuli. The computer model accounted for observed variations in color percepts within an observer and the individual differences in perceptions between observers with differing L:M ratios.