Single-Cell Analysis of the Organization of the Primate Color-Vision System

In order to determine the behavioral significance of various physiological responses to stimuli, it is obviously important to have a good idea of what sort of behavior the animal exhibits to these stimuli. Thus if one wants to determine if a particular type of ganglion cell response functions as part of the animal’s color vision system one must first have some information about what sort of chromatic discrimination, if any, the animal is capable of making. Unfortunately, almost all of our evidence with regard to the psychophysics of color vision is from man, whereas most of our physiological evidence must inevitably be from other animals. One can minimize these difficulties by studying the physiology of color vision in an animal whose visual system is as similar as possible to man, or an animal on which there is considerable psychophysical data, or an animal from which it is fairly easy to obtain psychophysical evidence to correlate with the physiological findings. The macaque monkey actually satisfies all of these criteria: Its visual system anatomically, from the retina to the cortex, is essentially identical to that of man; it has been studied behaviorally a number of times and has been clearly shown to have a trichromatic color vision system which is in most regards the same as the human; and finally, it is comparatively easy to obtain psychophysical data from the monkey. For these reasons we have chosen to study the physiology of color vision in the macaque monkey.