Walsh & Hoyt: Trichromacy, Color Opponency, and Imagery in Achromatopsia

Not all color perception is lost in achromatopsia. Several methods have established that some aspects of color processing derived from the function of the cones and retinal ganglion cells of the parvocellular pathway can still be discerned in achromatopsic patients. Thus, both trichromacy and color opponency have been shown in photopic spectral sensitivity curves and evoked potential or psychophysical measures of chromatic contrast sensitivity. Likewise, performance with anomaloscope testing can resemble an anomalous trichromat rather than a monochromat, despite the personal experience of the world in monochromatic ""shades of gray"". On the other hand, some impairment in spectral sensitivity curves occurs in some patients, suggesting that there is some extrastriate contribution to chromatic contrast.