News/Notices

Feb. 17, 11:45, Wei Ji Ma. Optimality and Probabilistic Computation in Visual Categorization

Temporal dynamics of the venetian blind effect

Joshua Dobias, Rutgers

When square wave gratings are viewed binocularly with lower luminance or contrast in one eye, the individual bars of the grating appear to rotate around a vertical axis (Venetian blind effect).  The effect has typically been thought to occur due to retinal disparities that result from irradiation and, therefore, are entirely entoptic.  If so, the visual system should process disparities from a luminance or contrast disparity and a geometric disparity at the same rate.  Studies of motion-in-depth using geometric disparities have shown that the visual system becomes unable to process depth cues when the cues are oscillated at frequencies greater than 5 Hz.  By changing contrast and geometric disparity cues over time, the set of experiments measured the frequency at which both the perception of motion-in-depth and the perception of depth diminish.  The perception of motion-in-depth decreased near 1.1 Hz and the perception of depth decreased near 1.3 Hz; both of which are lower than the frequency where depth from a geometric disparity diminishes (near 4.8 Hz).  The differences between the dynamics of depth from geometric and contrast disparities suggest that the perception arises from separate neural mechanisms.