When and where is binocular rivalry resolved in the visual cortex?

Anatomically "early" visual areas including striate cortex (V1) are known to play a role in the resolution of binocular rivalry. However, the time course of such activity and its relationship with subjective perception are unclear. The present study used an intermittent stimulation design to measure event-related potentials (ERPs) associated with perception during binocular rivalry and during physical alternations of the same stimuli. When gratings of high or low spatial frequencies were presented in physical alternation, the amplitude of the earliest cortical ERP component (the C1, at 60-100 ms) was larger for high spatial frequencies. When the same two stimuli competed during rivalry, however, C1 amplitudes were equivalent for perceptions of high versus low spatial frequency. These findings suggest that rivalry is not resolved before or during the initial cortical response at 60-100 ms. At longer latencies (approximately 130-160 ms), however, occipital ERPs with similar topographies and estimated sources as the C1 differed according to perception in both the rivalry and physical alternation conditions. These results suggest that during rivalry, neural activity coupled with the dominant percept first emerges in anatomically early visual cortex, but at delayed latencies.