82 Mechanisms of stereopsis in monkey visual cortex GIAN F. POGGIO Department of Neuroscience, The Johns Hopkins University, School of Medicine, Baltimore MD 21205, USA We investigated the stereoscopic properties of single neurons in striate (VI) and prestriate (V2, V3-V3A) cortex of alert rhesus monkey (trained to attend the fixation point). Many neurons have 'cyclopean' properties, giving uniquely binocular responses to random dot patterns; some of these were disparity selective for line stereograms (depth neurons), and some were not (flat neurons). Most have complex receptive fields. Three neural stereo systems may be recognized. The Zero disparity system includes neurons with sharply tuned responses at or near-zero disparity (Tuned excitatory, Tuned inhibitory), as well as disparity insensitive neurons (Flat); these all may signal the reference depth plane about the fixation distance. The Near and the Far disparity systems include neurons tuned to larger disparities, crossed or uncrossed (Tuned Near and Tuned Far), and neurons excited by disparities on one side of zero but inhibited by disparities on the other side (Near and Far); these may signal relative depth. The cyclopean responses to random-dot stereograms could result from the spatial arrangement of the functional components of the neuron's receptive fields, being composed of numerous discrete sites or subfields, with the subfields in one eye functionally linked with subfields of the appropriate positional disparity in the other eye. Stereopsis: some computational reflections TOMASO POGGIO Department of Brain and Cognitive Sciences, Massachussetts Institute of Technology, Cambridge, MA 02139, USA Bela Julesz' invention of random-dot stereograms not only triggered a large body of psychophysical experiments. It was also one of the reasons for the prominent role that theories of stereo vision had in the early and middle years of computer vision. Stereopsis is an example of the inverse problem of vision and the many solutions that have been proposed are themselves examples of the general computer vision approach of exploiting natural constraints. Central to stereo is the correspondence problem. Patchwise correlation of simple image measurements is one of the oldest algorithmic approaches to the correspondence problem and is the technique used in Julesz' Automap. The paper will discuss this basic idea from the point of view of computation and in terms of physiological and psychophysical correlates. A similar simple principle may play a central role also in other visual functions both low- and high-level, such as motion computation, object recognition and visual learning.
Spatial Vision (continued as Seeing & Perceiving from 2010) – Brill
Published: Jan 1, 1993
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