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Teng Leng, Zijiang J He; On the initiation and spreading of interocular suppression from binocular vertical contours. Journal of Vision 2003;3(9):452. doi: 10.1167/3.9.452.
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© ARVO (1962-2015); The Authors (2016-present)
Here we further our finding (He & Ooi, VSS02) that binocular figural contours (frames surrounding a rivalry stimulus) instigate binocular rivalry. Specifically, the dominant features in the rivalry zones neighboring the binocular vertical contours are features carried by the implicit half-occluded zones. Once triggered, these features spread their dominance to the remaining rivalry stimulus leading to suppression of features in the corresponding implicit non-half-occluded zones. In Test 1, red (RE) and green (LE) horizontal rectangles (2.77×0.57 deg) were shown on a white background, followed 0.5–1 sec later, by a binocular black vertical bar (0.29×1.64 deg). Observers saw red to the right of the vertical bar and green to the left, confirming that dominance is triggered from the implicit half-occluded zones. In Test 2, observers tracked their rivalry percept in two displays: (i) both eyes saw a large vertical grating (4.7cpd) background while only one eye saw a circular patch of horizontal grating (target, 0.98 deg); (ii) the orientations of the background and target gratings in display (i) were rotated 90 deg. Higher predominance for the target was found in display (ii) with horizontal background, underscoring the propensity of binocular vertical contours to trigger rivalry in (i). Test 3 extended the observation by Shimojo & Nakayama (1990). Binocular vertical bars were placed on a larger binocular background of horizontal grating. In one eye, solid rectangles were placed adjacent to and straddling the vertical bar. As predicted, the rectangle in the implicit half-occluded zone remained dominant, while the other rectangle tended to be suppressed by the background grating. Of interest, the suppression began at the zone adjacent to the vertical bar and spread to the remaining area of the rectangle. Altogether, our findings suggest that rivalry initiation and spreading operate at the level where half-occlusion is registered by the eye-of-origin signal.
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