Orientation discrimination in cyclopean vision

AbstractUsing a dynamic random-noise display we measured orientation discrimination threshold for two kinds of cyclopean bar and for a cyclopean edge. Ocular vergence was monitored by means of nonious lines. Orientation discrimination threshold for a cyclopean bar or cyclopean edge fell to a minimum at some disparity between about 2 and 50 min arc. For the three subjects tested with bars, the minimum value of discrimination threshold lay between 0.6 and 1.5 deg, and for the two subjects tested with the edge between 0.7 and 2.0 deg. The lowest discrimination thresholds for the cyclopean bars were similar for crossed and uncrossed disparities for all three subjects tested. Matched depth increased smoothly with increasing disparity through a range over which orientation discrimination threshold fell and then levelled out. We conclude that the processing of the depth of a cyclopean form is dissociated from the processing of the orientation of that same cyclopean form. We suggest that orientation discrimination of cyclopean form is determined by the relative activity of binocular, disparity-sensitive, orientation-tuned neurons