Visual Acuity of the Cat estimated from Evoked Cerebral Potentials

Abstract

THE ability to distinguish between a striped target or a grating and a non-striped target, when the average intensity is held constant, depends on the relative intensity (contrast) and size of the light and dark stripes. Contrast and stripe size, however, are not independent in that the minimum (threshold) contrast necessary to detect a grating varies with the spatial frequency (cycles/degree of visual angle) of the grating. The function relating contrast sensitivity, the reciprocal of threshold contrast, to spatial frequency is the contrast sensitivity function. When expressed this way, peak contrast sensitivity is found at moderate spatial frequencies, with sensitivity declining slowly at lower spatial frequencies and rapidly at higher spatial frequencies¹. At maximum contrast, the highest spatial frequency (finest grating) that is seen as a grating is a measure of the spatial resolution of the visual system and can be considered a measure of visual acuity².