Neuronal mechanisms underlying stereopsis: how do simple cells in the
visual cortex encode binocular disparity?
Citation Info
Gregory C. DeAngelis, Izumi Ohzawa, and Ralph D. Freeman (1995)
Neuronal mechanisms underlying stereopsis: how do simple cells in the
visual cortex encode binocular disparity?
Perception 24: 3-31.
Abstract
Binocular neurons in the visual cortex are thought to form the neural
substrate for stereoscopic depth perception. How are the receptive fields
of these binocular neurons organized to encode the retinal position
disparities that arise from binocular parallax? The conventional notion is
that the two receptive fields of a binocular neuron have identical shapes,
but are spatially offset from the point of retinal correspondence (zero
disparity). We consider an alternative disparity-encoding scheme, in which
the two receptive fields may differ in shape (or phase), but are centered
at corresponding retinal locations. Using a reverse-correlation technique
to obtain detailed spatiotemporal receptive-field maps, we provide support
for the latter scheme. Specifically, we show that receptive-field profiles
for the left and right eyes are matched for cells that are tuned to
horizontal orientations of image contours. However, for neurons tuned to
vertical orientations, the left and right receptive fields are
predominantly dissimilar in shape. These results show that the striate
cortex possesses a specialized mechanism for processing vertical contours,
which carry the horizontal-disparity information needed for stereopsis.
Thus, in a major modification to the traditional notion of the neural basis
of stereopsis, we propose that binocular simple cells encode horizontal
disparities in terms of phase at multiple spatial scales. Implications of
this scheme are discussed with respect to the size-disparity correlation
observed in psychophysical studies.
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