Spatial profile of disparity signal integration for fine depth judgment
Takahiro Doi, Takahiro Okada, Ichiro Fujita
Lab Cognitive Neurosci, Osaka Univ, Toyonaka
Acuity for perceiving stereoscopic depth is improved when a reference plane is available beside a test plane, suggesting an importance of combining binocular-disparity signals from different locations. We present a functional description of how the brain spatially weighs and integrates disparity signals for stereoacuity. The spatial weighting function, estimated by a psychophysical reverse-correlation method, peaked near the disparity boundary between the test and reference planes. The weights were smaller for areas distant from the boundary. At 4 deg from the disparity border, the weight was 10% of the peak (for stimuli with 3.5 deg eccentricity). Subjects showed a curious perceptual bias to judge a depth plane to be near regardless of its disparity when the other plane had binocularly uncorrelated noise. We estimated a weighting function for this bias. It showed a similar profile to but smaller weights than the weighting function for veridical judgment. The results suggest that selective use of signals from the disparity boundary underlies veridical fine depth judgment and task-irrelevant perceptual bias.