Perceptual Completion across the Fovea under Scotopic/Mesopic Viewing Conditions

Abstract

Perceptual completion has been shown to occur across the blind spot, across the blue-blind region of the fovea, and across blind fields created by retinal scotomas. The purpose of this study was to determine whether perceptual completion can also occur across the dark-adapted fovea. The central fovea, which contains only cones, is blinded at low light levels, when rod vision is still possible in the periphery. Does the visual system “fill in” features across the center of gaze at low light levels? To answer this question, three dark-adapted subjects were asked to report the presence or absence of a circular gap in a field, line, or checkerboard pattern viewed under high scotopic or low mesopic conditions. The gap in the field, line, or pattern appeared on half the trials, positioned either at the fovea or 4° in the periphery. All three subjects were significantly more likely to report “no gap” on foveal gap trials than on peripheral gap trials for field and line stimuli; results for the patterned stimuli were inconclusive. These results indicate that perceptual completion of both fields and lines occurs across the fovea under high scotopic/low mesopic viewing conditions. The completion of lines suggests mechanisms involving cortical circuitry.