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Yong Su, Zijiang J. He, Teng Leng Ooi; The critical role of boundary contours in the early temporal processing of binocular rivalry. Journal of Vision 2006;6(6):853. doi: https://doi.org/10.1167/6.6.853.
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When one eye views a vertical grating disk (SF=4cpd, contrast=95%) surrounded by a horizontal grating background and the fellow eye views only the horizontal grating background, the observer perceives the vertical grating disk almost continuously despite the corresponding retinal area receiving a horizontal grating. This is because the monocular boundary contour (MBC) that defines the disk is a critical factor in perceptual dominance (Ooi et al, 2005). Is the preeminence of boundary contours evident at the early temporal stage of binocular rivalry processing? We investigated this question using three types of rivalry displays: (i) The abovementioned MBC-display; (ii) A binocular boundary contour (BBC)-display, in which a circular/disk area of the horizontal grating background that corresponded to the vertical disk in the MBC-display was phase shifted by 180deg to create a horizontal grating disk; (iii) A typical rivalry display (horizontal vs. vertical grating disks). We varied the stimulus presentation duration (30, 50, 100, 150 msec) and disk size (1.0, 1.3, 1.6, 1.9 deg). Observers responded with four possible percepts: global grating disk, piecemeal, checkerboard, indeterminate. We found that the stimulus duration for perceiving the global grating disk above 50% frequency was 30 msec for the smaller MBC-displays (<1.6deg), and 50 msec for the larger (1.9deg) MBC-display. In contrast, for the BBC and typical rivalry displays, observers seldom saw the global grating disk percept (<5%) for all the durations and sizes tested. These findings reveal the primacy of boundary contours, and that rivalry begins earlier (temporal) than previously thought.
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