Early neural correlates of familiarity during binocular rivalry

n infrequent visual stimulus-a "deviant"-yields a more negative event-related potential (ERP) 200 ms after the event than frequent visual stimuli-"standards": the visual mismatch negativity (vMMN). We sought the vMMN during binocular rivalry by presenting 80% standards-an 180° phase shift in one grating to one eye every 500 ms and the same phase shift in an orthogonal grating to the other, and 20% deviants-either by swapping the phase-shifting gratings between the eyes or by rotating them 45°-to 16 participants who pressed keys to report their experiences of rivalry. We counterbalanced which stimuli were standards and deviants. We found only a more positive ERP for the standard 100 ms after the event. This is not only opposite to the vMMN, but opposite to what would be expected from adaptation. We are exploring the parameters of this finding, such as whether it is something about rivalry (by making the stimuli identical in the two eyes) or something about the task (by relieving the participant of the necessity to record rivalry). Our initial results indicate it has something to do with rivalry, possibly because its perceptual changes make deviants seem more frequent then they are.