DETECTION AND DIRECTION DISCRIMINATION PERFORMANCE WITH FLICKER GRATINGS IN PERIPHERAL-VISION

Detection and direction discrimination experiments were conducted with luminance and flicker gratings. The flicker gratings had bars made up of static random pixels interspersed between other bars with flickeri ng random pixels. All experiments were carried out in peripheral visio n with grating images centered at 8 deg eccentricity in the superior r etina. Detection of flicker gratings (i) was independent of pixel size , (ii) declined with spatial frequency in the range 1-4 c/deg, and (ii i) improved with stimulus area (number of grating cycles). Detection p erformance with a flicker grating was comparable to that obtained with a low-contrast (0.01) Luminance grating, and the results suggest that the spatial structure of a flicker-domain stimulus is based upon sign als which are weak compared to the maximum signals attainable with a l uminance-domain stimulus. With the detectability of flicker and lumina nce gratings equated, d' for discriminating the direction of motion of a luminance grating increased with step size (1/12 to 1/4 cycle) wher eas direction discrimination performance with a flicker grating remain ed unchanged and at chance levels. Under the conditions tested, there was no evidence that the motion of a flicker-domain stimulus could be processed peripherally. Constraints on alternative models of motion pr ocessing are discussed.