Spatial tuning of static and dynamic local stereopsis.

The range of spatial tuning for channels that process static and dynamic disparities was investigated in the central visual field by measuring stereoscopic thresholds as a function of the difference in size of spatially filtered bar-like patterns presented to the two eyes. Spatial tuning functions were revealed by an elevation of stereothreshold as the difference between the widths of bar patterns increased. Functions tuned to low spatial frequencies (0.075-2 c/deg) were classified as transient since their stereosensitivity was greater for dynamic (1 Hz) than static disparities. Functions tuned to high spatial frequencies (2.4-19 c/deg) were classified as sustained since their stereosensitivity was equal for dynamic and static disparities. When equal width patterns were presented to the two eyes, stereothreshold increased with spatial periods greater than 0.4 deg according to a constant 6 deg phase disparity. This size-disparity correlation suggests that large disparities are processed by spatial filters tuned to disparities proportional to their receptive field dimensions.