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Michiteru Kitazaki, Kazuo Mase; Contrast effect of spatial context on binocular rivalry is modulated by eccentricity and binocular depth. Journal of Vision 2005;5(8):3. doi: 10.1167/5.8.3.
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Spatial context influences binocular rivalry. The predominance of a rivalry target is facilitated by globally coherent stimuli (eg Sobel & Blake, 2002). In contrast, if a rivalry target is surrounded by a background, the context-contradictory target is preferred in some cases (eg Paffen et al, 2003; Carter et al, 2004). The purpose of this research is to explore the contrast effect of spatial context on binocular rivalry, and its modulation of the rival target's eccentricity and the binocular depth separation between the target and the surrounding background. We presented a square (1.5x1.5 deg) consisting of sinusoidal gratings (2.0 cpd, 100% contrast, mean luminance 50.0 cd/m2, rightward or leftward slant 45 deg) dichoptically, of which the orientations were orthogonal for two eyes (Rivalry target). The rivalry targets were surrounded by a similar grating (10x10 deg), of which the orientation was identical to one of rivalry targets (Background). Thus, a rivalry target for one eye and the background were collinear gratings, and the other target and the background were orthogonal gratings. 7 naive subjects continuously reported the predominant orientation of the target grating for 180 s. In Experiment 1, the retinal eccentricity of the rivalry target was varied at 0.0, 0.75, and 1.5 deg by manipulating the position of the fixation point. In Experiment 2, we introduced binocular disparity to the background grating, which was in front of, on, or behind of the rivalry target (crossed or uncrossed disparity 0.1 deg). Most subjects showed the predominance of the rivalry target consisting of the orthogonal gratings over the collinear gratings (spatial contrast). The contrast effect of binocular rivalry decreased as the eccentricity increased (Experiment 1) and as the background was separated in depth (Experiment 2). These results suggest that the cortical processes for spatial contrast and binocular depth perception are concerned with the predominance during binocular rivalry.
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