Comparison of the Effects of Striate Cortex and Retinal Lesions on Visual Acuity in the Monkey

Abstract

Acuity falls sharply and predictably in man as fixation is shifted away from the test stimulus. If the same "eccentricity" function applies to the monkey, then it can be shown that striate cortex lesions produce a smaller acuity impairment than is predicted by electrophysiological maps of the projection of retina onto the cortex. It is seen in this study that retinal lesions of the fovea and adjacent parafovea produce a more severe drop in acuity than corresponding cortical lesions, and therefore the surprisingly slight effects of the latter cannot be explained in terms of a relatively higher parafoveal acuity in the monkey. The discrepancy between retinal and cortical effects is unlikely to be due to the development of "supersensitivity" at the edge of the cortical lesions. An explanation is proposed in terms of lateral spread of information at retinal and/or geniculate stages of the visual system.