Inhibition around visual stimuli

Abstract

Kirschfeld and Kammer (1999), and independently Kanai, Sheth and Shimojo (2004), proposed that an inhibitory wake trails a moving visual stimulus, and a bow-wave like region of excitation precedes it. Using the perceived luminance of a small flash as a psychophysical probe, I demonstrate that indeed a region of significant inhibition extends behind a moving stimulus. However, in contradiction to these models, the region of inhibition also extends ahead of the moving stimulus, as well as to the side. In regions immediately around the moving stimulus, the average effect size (d) is estimated to be greater than three. Effects of the visual stimulus without its motion attribute, and masking effects of the moving stimulus, were controlled for.