Neural activity during binocular rivalry in the anesthetized monkey

When humans or monkeys are stereoscopically shown a pair of dissimilar images they experience a sequence of spontaneous perceptual fluctuations known as binocular rivalry. This phenomenon has been studied extensively, and has recently been used as a means to investigate neural mechanisms of perceptual organization. While it is now known that several areas in visual cortex participate in rivalry, the fundamental basis and origin of the spontaneous alternations remain poorly understood. Some evidence suggests that conscious perception is a critical component, since multistable perception is intimately related to attention and awareness. Yet, it is also possible that the brain, given a pair of discordant visual stimuli, automatically generates a sequence of state-changes, alternately processing each conflicting pattern in turn. Such automatic changes could be initiated by passive, free-running sensory networks, or alternatively by more complex mechanisms involving a variety of brain areas. In either case, the subjective perception experienced during waking would simply reflect these automatic processes. The present study addressed these issues by measuring neural activity (single unit responses, multiunit activity, and local field potentials) in the cortex of anesthetized monkeys under visual stimulus conditions that would normally give rise to binocular rivalry. Multiple electrodes afforded the simultaneous monitoring of sites in several striate and extrastriate visual areas. Analysis focused on the identification and characterization of spontaneous state-changes related to the conflicting stimuli that might serve as a basis for perceptual alternation