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Sang-Hun Lee, Randolph Blake; V1 activity is reduced during binocular rivalry. Journal of Vision 2001;1(3):448. doi: 10.1167/1.3.448.
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During binocular rivalry, one of two incompatible monocular stimuli is erased from perceptual awareness for seconds at a time. Activity in several “high” level visual areas modulates in synchrony with fluctuations (Tong et al 1998) and transitions (Lumer et al 1998) in rivalry dominance. Recently, Polansky et al (2000) found that BOLD signals in V1 of humans viewing rival gratings differing in contrast are larger when the high contrast pattern was dominant compared to when the low contrast pattern was dominant, suggesting that neural events associated with rivalry transpire in primary visual cortex. To examine this possibility further, we used a block design to compare BOLD activations during three viewing conditions: i) orthogonally oriented gratings yielding rivalry, ii) separate members of the rival pair alternately presented to left and right eyes in a temporal sequence mimicking rivalry alternations, and iii) physical superposition of the two gratings to create a “plaid” shown alternately to the two eyes. BOLD signals were measured in a 1.5T scanner while observers viewed patterns via anaglyphic presentation. Retinotopic mapping demarcated boundaries of visual areas, and localizer trials identified ROIs within those areas. In V1 activation level during rivalry fell midway between the “mimic” and the “plaid” conditions, implying that stimulus conditions producing rivalry are distinguishable in V1 from those associated with superimposition of the two components. In areas V2, V3 and V4 BOLD signals for the rivalry condition more closely approximated those for the “mimic” condition, implying that neural events associated with the suppressed rival target become increasingly indistinguishable from those associated with the physical absence of that target.
Discovery Program (Vanderbilt University) and the Office of Naval Research.
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