Binocular Rivalry: Evaluating the Role of Theta Power as a Neural Index of Conflict

Binocular rivalry (BR) occurs when each eye is presented with mutually incompatible images, and the brain alternates between perceiving one image, the other or occasionally a mashup of both. Addressing a decades-old suggestion, it has been shown that the competition between alternative representations in BR induces a pattern of neural activation resembling that occurring in cognitive conflict, eventually leading to fluctuations between different perceptual outcomes in the case of steep competition. This is reflected by known signatures of conflict dynamics, namely, an increase in fronto-medial theta oscillatory power (5-7 Hz) in the EEG right before perceptual transitions and a decrease thereafter, as well as a decrease in parieto-occipital alpha oscillatory power (8-12 Hz) prior to perceptual transitions and an increase thereafter. However, according to a growing body of research, frontal activity during BR might be related to report processes rather than perception processing per se. Such conflation is related to the use of continuous report protocols. To circumvent this confound, here, we present a BR study using an onset rivalry (rather than continuous rivalry) protocol that dissociates the moment of report from the period of stimulus presentation. The findings revealed higher fronto-medial theta power for rivalrous than for non-rivalrous stimuli both resulting in equivalent perceptual classification, despite the absence of a motor confound. In addition, we found greater parieto-occipital alpha suppression for rivalrous stimuli. The results presented here advance our understanding of how cognitive conflict monitoring and resolution may influence perception in the event of competition from incompatible sensory patterns.