Depth discrimination for transient and sustained images by the human stereoscopic system
Maki Takano, Takahiro Doi, Ichiro Fujita
Frontier Biosciences, Osaka University, Toyonaka, Japan
A few psychophysical studies propose that stereoscopic depth is processed
by different mechanisms, depending on the temporal properties of visual inputs.
We tested this hypothesis by considering the recent physiological findings
that neurons in the dorsal and ventral pathways compute the disparity energy
and the global-match solution to the stereo correspondence problem, respectively.
Subjects discriminated the depth of dynamic random-dot stereograms (RDSs).
The pattern refresh rate of RDSs was varied across blocks of trials. In a single
block, we varied disparity sign and the ratio between binocularly correlated
and anti-correlated dots. At a fast refresh rate (e.g., 43 Hz), subjects perceived
reversed depth for anti-correlated RDSs (aRDSs), and no depth when the two
groups of dots balanced. At a slow refresh rate (e.g., 5 Hz), the reversed
depth for aRDSs was weak, and correct depth was perceived at the balanced point.
These results suggest that the disparity-energy and binocular-matching computations
underlie stereopsis for transient and sustained visual inputs, respectively.