Abstract
Leone, Blakeslee & McCourt (VSS 2011) reported a significant age-related reduction in the perceived contrast of gratings in the lower versus upper visual field, in free viewing. We extend these findings by assessing suprathreshold contrast perception at additional spatial and temporal frequencies, under conditions of central fixation. In Experiment 1 participants (N=64) matched the contrast of gratings (1°x 40°; 0.0625 or 1.875 c/d; 5 or 50% contrast) in the upper and lower visual fields (±7.5° eccentricity) while maintaining central fixation. As previously found in free viewing, at all contrasts and spatial frequencies there was an age-related reduction in the perceived contrast of gratings in the lower versus upper visual field. Experiment 2 replicated Experiment 1 except that grating contrast was temporally counterphased at 1 or 4 Hz. Temporal modulation eliminated the age-related visual field processing asymmetry found for static stimuli. In the low contrast, low spatial frequency condition (5%; 0.0625 c/d), temporal contrast modulation at both 1 and 4 Hz actually reversed the age-related reduction in perceived contrast in the lower visual field such that perceived contrast in the lower versus upper visual field increased with age. These results are discussed with respect to an age-related magnocellular pathway deficit where sensitivity loss is greatest for static stimuli, and where disuse supersensitivity may result in compensatory (high gain) responses to preferred (temporally modulated) stimuli.
Meeting abstract presented at VSS 2012