Abstract
EEG decoding provides a powerful tool for examining the temporal dynamics of representational content and can help adjudicate between models of consciousness that differ in whether awareness occurs rapidly or slowly. In an effort to isolate the neural correlates of consciousness (NCC) and further understand the time course of conscious perception, we applied ERP decoding to a binocular rivalry paradigm, in which different orientations were briefly flashed to the two eyes and competed for awareness. Subjects were aware of one orientation and suppressed the other. We compared decoding accuracy for the orientation that was consciously perceived and the one that was suppressed. We tested two predictions: 1) if the Global Neuronal Workspace Theory (GNWT) is correct, conscious perception should occur ~300-500 ms after stimulus onset (i.e., the time range of the P3b component); 2) if the Visual Awareness Negativity (VAN) reflects conscious perception, conscious perception should occur at ~200 ms after stimulus onset. A red circle–shaped sinusoidal grating was flashed briefly to one eye and a green grating was simultaneously flashed to the other eye. Participants were instructed to report the color of the stimulus they perceived (red/green), and we separately decoded the orientation of the perceived and unperceived gratings. We could decode both gratings initially, but decoding accuracy increased for the perceived grating at ~200 ms, whereas decoding accuracy on the same trial for the unperceived grating decreased. Thus, awareness impacts the information that is available about a given stimulus relatively rapidly, consistent with the timing of the VAN and earlier than would be expected from GNWT. More broadly, this novel decoding provides a new means of isolating NCCs.