VARIABILITY IN GAMMA ACTIVITY DURING OBSERVATION OF AMBIGUOUS FIGURES
Observing ambiguous figures induces spontaneous perceptual reversals. Since gamma oscillations are considered relevant for object representation and neural integration (binding problem), reversal-related transitions between brain states should be accompanied by characteristic modulations of gamma activity. Particularly, previous studies suggest that gamma activity is enhanced during perceptual reversals. We examined this finding through time-frequency analysis of EEG traces in n=16 subjects, using a new experimental paradigm which compares perceptual reversal with stability conditions and provides a better access to the reversal instant. In some subjects, gamma activity differed significantly between conditions, but was indistinguishable after baseline correction. Oscillatory activity showed temporal and spatial modulations which, however, were not specific for the experimental condition. These findings are in contrast with those of a recent study analyzing grand averages. We briefly discuss the relation between individual and group level results and comment on our graphical statistical approach.