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Shih-Cheng Yen, Charles M. Gray; Properties of contour integration in a macaque monkey. Journal of Vision 2001;1(3):36. doi: 10.1167/1.3.36.
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© ARVO (1962-2015); The Authors (2016-present)
As a prelude to investigating the physiology underlying contour integration in the macaque visual system, we conducted two sets of psychophysical experiments to characterize the properties of contour integration in a macaque monkey. First, we studied the latency of contour perception in the macaque visual system. The stimuli consisted of an array of 160 Gabor patches, with 8 Gabor patches aligned to form a closed contour. Reaction times were measured while the animal was required to either make a saccade to the contour within 600 ms of stimulus onset, or hold fixation for 750–1250 ms after stimulus onset and then saccade to the contour. We propose that the difference in reaction times between the first task, which contained both perceptual and motor components, and the second task, which was predominantly a motor task, may be used to estimate the latency of contour perception. Our results showed that this difference may be as small as 35 ms. In the second set of experiments, we studied the interactions between motion coherence and contour closure in a contour detection task. We trained the animal to perform the task using both stationary Gabor patches, as well as Gabor patches that moved within a stationary window. In the latter case, the Gabor patches on the contour moved either coherently in the same direction, or incoherently in one of two directions orthogonal to the orientation of the Gabor patch. We found that compared to static contours, coherent motion significantly increased the salience of both open and closed contours, while incoherent motion significantly decreased the salience of open contours but did not change the salience of closed contours. This suggests that cells activated by a closed contour may be able to compensate for the degradation in salience that results from the addition of incoherent motion.
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