New paper: EEG Decoding of Conscious versus Unconscious Representations During Binocular Rivalry

Krisst, L. C., & Luck, S. J. (in press). Electroencephalographic decoding of conscious versus unconscious representations during binocular rivalry. Journal of Cognitive Neuroscience. https://doi.org/10.1162/jocn_a_02308

A hotly debated question in the science of consciousness revolves around the temporal dynamics of conscious perception – does visual information become conscious early or late the cortical hierarchy? To address this question, we decoded orientation information during binocular rivalry. We used an intermittent stimulus approach design which allowed us to time lock the EEG data to the onset of the stimuli and compare the decoding accuracy of conscious and unconsciousness representations on the same trial using full scalp EEG. This unique experimental paradigm 1) eliminated time locking to the response – typical in reversal based rivalry paradigms, and 2) avoided problems introduced by the contrastive approach which is often prey to contamination of neural signals involved in pre – and post – perceptual processing.

In this binocular rivalry paradigm, a different orientation was presented to each eye on each trial. So, on every trial participants are aware of the orientation in one eye but not the orientation in the other eye. On each trial, they reported l which image they could see.

Instead of simply looking at the magnitude of the ERP, we used decoding to look at the informational content represented in the brain. Specifically, we examined the ability to decode the orientation information that the participants reported being aware of, and the other orientation that they were unaware of, at the very same time.

We found that decoding accuracy was significantly greater for the consciously perceived orientation (Fig. a) than for the unperceived orientation, beginning at ~160 ms after stimulus onset (see figure). This finding supports theories of consciousness which argue that conscious perception arises early in the cortical hierarchy. Although the results are not definitive evidence against theories suggesting a slower onset of consciousness awareness (e.g., through interactions between visual cortex and frontal cortex), such models would need to be revised or expanded to incorporate these findings of a quick onset.