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Abstract:
Neurophysiological studies using bistable visual patterns have revealed a diversity of roles for individual neurons with respect to the ultimate percept. Furthermore, studies have demonstrated that the incidence of percept-related neurons in different areas appears to be similar during ambiguous perception brought about by binocular rivalry (BR) and structure from motion (SFM). One interpretation of these results is that there exists a specialized subset of neurons whose responses are inextricably linked with perception, regardless of the exact stimulus. The present experiments address this hypothesis by examining perception-related responses at individual recording sites during the presentation of two or more fundamentally different ambiguous patterns. Multielectrode recordings were performed from parietal areas in two macaque monkeys, and neurons were tested with bistable binocular rivalry flash suppression (BRFS) and SFM patterns. In agreement with previous studies, we found that in area MT, activity at a subset of neural sites was modulated according to the perceptual state. However, although their relative fraction was similar in the two cases, the particular sites were only partially overlapping, even when the stimuli were adjusted to contain same directions of motion. Moreover, during BRFS, at some sites perception-related activity was idiosyncratic for specific pattern pairs. For example, perceptual dominance was marked by activity increases for one suppressed pattern but not for another. These results suggest that the expression of perceptual dominance in the visual cortex is closely linked to the resolution of ambiguity among specific visual features, and may therefore be closely related to mechanisms of perceptual organization in natural vision.
