On “A three-stage color model”

to a first approximation, that a light of any spatial frequency that appears whitish to humans will either appear whitish to macaques, or be responded to as a null stimulus by the ensemble of macaque cells that comprise a particular chromatic system. COLOreD LIGHTS In regard to colored lights, an opponent cell will indeed increase its firing to luminance increments (as well as to equiluminant color increments) but this does not at all imply confounding; rathe, r, in both cases, the cell will signal more color. Alternatively stated, when one increases the luminance (or radiance, or energy, etc.) of a colored light, any theory must predict that its chromaticness (as well as its whiteness) will increase. Otherwise, incrementing the luminance of a colored light would be equivalent to dcsaturating it. For example, within opponent theory, if one increments the luminance of a red light, then not only must nonopponent cells increase firing so there is more whiteness, but also opponent, say R/G, cells must increase firing so that there is more redness, thereby producing at least approximate invariance of the apparent saturation of the light. (Of course, if one increments the light's redness, i.e. purity, at equal luminance, then nonopponent cells will not be affected but opponent cells must again increase firing; to signal increased saturation of redness.) Therefore, for colored lights, the De Valois' statement that an opponent cell will fire to both luminance and color changes is absolutely true, but confounding is not involved-rather, the opponent cell is in both cases signaling more color, as it must. response patterns of LGN cells. spectral sensitivity, and a new color model. certain aspects of visual behavior by reference to the observed characteristics of the anatomy and physiology of the visual system. Although the Standard Model has served us well, its account of several phenomena of interest is less than completely satisfactory. Motivated in part by our recognition of these limitations, and in part by certain new anatomical and physiological reports sug