Individual peak gamma frequency predicts switch rate in perceptual rivalry

Perceptual rivalry-the experience of alternation between two mutually exclusive interpretations of an ambiguous image-provides powerful opportunities to study conscious awareness. It is known that individual subjects experience perceptual alternations for various types of bistable stimuli at distinct rates, and this a stable, heritable trait. Also stable and heritable is the peak frequency of induced gamma-band (30-100 Hz) oscillation of a population-level response in occipital cortex to simple visual patterns, which has been established as a neural correlate of conscious processing. Interestingly, models for rivalry alternation rate and for the frequency of population-level oscillation have both cited inhibitory connections in cortex as crucial determinants of individual differences, and yet the relationship between these two variables has not yet been investigated. Here, we used magnetoencephalography to compare differences in alternation rate for binocular and monocular types of perceptual rivalry to differences in evoked and induced gamma-band frequency of neuromagnetic brain responses to simple nonrivalrous grating stimuli. For both types of bistable images, alternation rate was inversely correlated with the peak frequency of late evoked gamma activity in primary visual cortex (200-400 ms latency). Our results advance models of inhibition that account for subtle variation in normal visual cortex, and shed light on how small differences in anatomy and physiology relate to individual cognition and performance.