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Traveling waves in visual cortex during binocular rivalry
Dr. David Heeger
Tuesday, March 08, 2005, 01:00pm - 02:00pm
New York University, Department of Psychology and Center for Neural Science
When the two eyes view dissimilar patterns, one experiences a perceptual illusion called binocular rivalry. Instead of seeing both patterns superimposed, they are perceived in alternation. What makes this phenomenon remarkable is the dissociation between a constant physical stimulation and fluctuating perceptual experience. In spite of widespread interest, and an impressive volume of high-quality work on this topic, many of the central questions concerning the neural processing underlying binocular rivalry remain open. Particularly controversial is the role of primary visual cortex (V1) in rivalry. To address this controversy, we are capitalizing on an interesting aspect of the perceptual phenomenon; during an alternation, one sees a traveling wave in which the dominance of one pattern emerges locally and expands progressively as it renders the other pattern invisible. We have used fMRI to measure traveling waves of cortical activity in early visual areas accompanying perceptual traveling waves. Our results demonstrate: 1) that competition between the two rival stimuli is implemented by neural circuits in V1; 2) that for the consequences of this neural competition to be perceived, activity must advance to higher visual areas; and 3) that attention, mediated by feedback, plays a crucial role in promoting neural activity from V1 to higher visual areas.