Abstract
Stimuli extending through the receptor-free blind spot region of the retina appear filled in. However, stimuli extending into the blind spot without passing through to the opposite side appear cut off at the blind spot boundary. Here we test whether the perceived cut-off position at the blind spot boundary is solely determined by the anatomical position of the blind spot, or whether it can be influenced by visual motion. We used a haploscopic setup that allowed presenting stimuli independently to each eye. A sinusoidal grating was presented within a rectangular aperture that extended into the blind spot (or—for control purposes—ended in a Gaussian contrast edge at corresponding regions in the fellow eye). The grating was either drifting into or out of the blind spot region, or remained stationary while flickering in counterphase. Observers were asked to judge the perceived end point of the grating by moving pointers to the perceived cut-off position (presented binocularly next to the grating). In the fellow eye, the perceived end point was consistently shifted in the direction of motion, a replication of the well-known De Valois effect. At the blind spot, observers also perceived the cut-off point shifted in the direction of motion, meaning that observers perceived the grating extending further into the blind spot when it drifted in that direction. This result points to a dynamic filling-in process dependent on visual motion that facilitates filling-in of spatiotemporal visual structure and works even if there is no stimulation at the opposite blind spot boundary.
Meeting abstract presented at VSS 2014