Abstract
In stereovision, images are slightly disparate, but usually correlated and synchronized between the two eyes. When an image in one eye is given a reversed luminance contrast (binocularly anticorrelated), or when the image sequence in one eye is given a time lag, there is no global-match solution to the stereo correspondence problem. Despite the absence of a global-match, disparity energy mechanisms can convey a nonzero depth signal. We examined whether human subjects can discriminate stereoscopic depth in anticorrelated random-dot stereograms (RDS) and in RDS with interocular delay. The subjects were asked to report whether the center portion of a dynamic RDS appeared nearer or farther than the annular portion. The direction of perceived depth was reversed in anticorrelated RDS with small interocular delay (12 ms). As the interocular delay increased, subjects' performance approached chance for both correlated and anticorrelated RDS. At intermediate interocular delay (108 ms), there was another depth reversal in which subjects chose the correct depth in anticorrelated RDS. These stereo judgments did not accompany perception of clear surface contours. In order to account for the psychophysical performance of perceived depth, we incorporated the temporal dimension into the standard disparity energy model. The amplitude of the model's disparity tuning curve gradually decreased as interocular delay increased, and even inverted at intermediate interocular delay. Thus, reversed depth perception for both anticorrelated RDS and interocular delay is accounted for by the disparity energy signals computed in early stereo processing stages.
Supported by grants from MEXT (17022025) and Takeda Science Foundation.