On the Neural Locus of Binocular Rivalry Suppression

Vanderbilt University, Nashville TN

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Abstract

Binocular rivalry refers to a state of the visual system that arises when the two retinal images are too disparate to be fused into a single coherent three-dimensional depiction of the world. During rivalry, portions of each retinal image are erased from visual awareness for seconds at a time. Rivalry suppression is a potentially powerful tool for determining whether other mechanisms precede or follow rivalry in the visual hierarchy, but to fully exploit it as a psychoanatomical tool, we should know the neural locus of binocular rivalry itself. Whereas some empirical results point to a relatively early locus of rivalry, other experiments have failed to provide any evidence that rivalry suppression interferes with the growth of several well-known visual aftereffects, which implies that the site of rivalry suppression is later than that of adaptation. However, recent neurophysiological research suggests that a key assumption underlying the rivalry/aftereffect studies may have been faulty. The experimenters assumed that during suppression a visual signal is completely eliminated, but it now seems that in early visual areas the effect of rivalry is a modest reduction of signal strength. By recasting the earlier work in light of the recent neurophysiology, the present study is intended to more rigorously test whether rivalry interferes with the growth of aftereffects, and thus relieve a longstanding controversy in vision research. For each of three visual aftereffects, participants will view with one eye an adapting stimulus at a carefully selected level of contrast, and a stimulus designed to instigate rivalry with the other eye.