Aging effects on vernier hyperacuity: a function of oscillation rate but not target contrast

Purpose. Most previous studies have shown static vernier acuity for high-co ntrast targets to be largely unaffected by aging; those examining adult age differences on oscillatory displacement thresholds have consistently repor ted marked age deficits. The goals of this study were to (1) measure the ag e deficit on oscillatory discrimination beyond that attributable to any cha nge in spatial discrimination by using the same target configuration for bo th task types and (2) determine whether an age-related change in the contra st response of the visual system contributes to age differences on static o r oscillatory discrimination. Methods. The displacement thresholds of young and old observers for a vernier task configuration were determined at two target contrast levels (0.08 and 0.64) for static and oscillating targets ( 2 and 6 Hz). Results. No age differences were seen on static displacement t hresholds at either high or low contrast. A marked age deficit that emerged when oscillation was increased was unrelated to target contrast or observe r contrast sensitivity. Conclusions. Age-related declines in oscillatory di scrimination beyond those attributable to spatial discrimination do not app ear to be attributable to optical factors nor to a decline in the contrast response of the senescent visual system. These findings are discussed in te rms of a functional decline in the magnocellular pathway, or "neural entrop y," possibly due to random cell loss.