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Abstract:
When left and right eyes are presented with composite patterns A þB and A-B, respectively, ambiguity can ensue between percepts reflecting ocular summation (A) and opponency (B) channels in primary visual cortex (Li and Atick, 1994; May, Zhaoping, and Hibbard, 2012). When A and B are foveal gratings having different drift directions (Shadlen and Carney 1985) or different orientations (Zhaoping, 2013), subjects more frequently perceive the ocular sum, A. This perceptual bias is weaker or absent in the periphery (Zhaoping, 2013, 2014). Here, I generalize these findings to color. A and B are static, colored, horizontal gratings, with random spatial phases. Each grating exhibits spatial alternations between its own pair of colors: e.g., one grating is red-green and the other is blue-yellow. Each monocular image, A þ B or A-B, typically displays a collection of hues. Observers briefly saw the dichoptic stimulus (e.g., 0.2 second) and reported whether it appeared more like reference A or B in color. The bias for ocular summation may be associated with a perceptual prior acquired through visual experience; its enhanced strength in the fovea is likely general across different visual feature dimensions, with top-down feedback (to implement visual analysis by synthesis) favored in central vision (Zhaoping 2013).
