Brightness induction and suprathreshold vision: Effects of age and visual field

A variety of visual capacities show significant age-related alterations. We assessed suprathreshold contrast and brightness perception across the lifespan in a large sample of healthy participants (N = 155; 142) ranging in age from 16 to 80. years. Experiment 1 used a quadrature-phase motion cancelation technique (Blakeslee & McCourt, 2008) to measure canceling contrast (in central vision) for induced gratings at two temporal frequencies (1. Hz and 4. Hz) at two test field heights (0.5° or 2° × 38.7° 0.052. c/d). There was a significant age-related reduction in canceling contrast at 4. Hz, but not at 1. Hz. We find no age-related change in induction magnitude in the 1. Hz condition. We interpret the age-related decline in grating induction magnitude at 4. Hz to reflect a diminished capacity for inhibitory processing at higher temporal frequencies. In Experiment 2 participants adjusted the contrast of a matching grating (0.5° or 2° × 38.7° 0.052. c/d) to equal that of both real (30% contrast, 0.052. c/d) and induced (McCourt, 1982) standard gratings (100% inducing grating contrast; 0.052. c/d). Matching gratings appeared in the upper visual field (UVF) and test gratings appeared in the lower visual field (LVF), and vice versa, at eccentricities of ±7.5°. Average induction magnitude was invariant with age for both test field heights. There was a significant age-related reduction in perceived contrast of stimuli in the LVF versus UVF for both real and induced gratings.