Rapid alternation of conscious and suppressed stimulus representations in the primate brain

Neural activity in the primate brain exhibits a rapid alternation between conscious and suppressed stimulus representations, a finding that challenges our understanding of consciousness. Previous research indicated that high-level visual cortex, responsible for processing visual information, shows minimal modulation during conscious perception [1, 2, 3]. However, no direct evidence of consciousness has been discovered within the brain.

In this study, researchers utilized Neuropixels recordings across multiple face patches in both inferotemporal and prefrontal cortex during a binocular flash suppression paradigm. This technique involves presenting one image while suppressing the other, which the individual perceives consciously. The researchers observed that during constant stimulus and perception, the brain alternated between conscious and suppressed micro-epochs about 15 times per second.

When the brain was experiencing a conscious micro-epoch, a clear signal of conscious perception was present, enabling accurate reconstruction of the conscious image from neural activity. In contrast, during suppressed micro-epochs, the pure signal tracked the suppressed stimulus, allowing the reconstruction of the suppressed image.

At the single-cell level, neurons demonstrated selective response to the conscious stimulus during conscious micro-epochs and to the suppressed stimulus during suppressed micro-epochs. Despite this apparent symmetry, the two epochs could be differentiated based on feature tuning, which was amplified during conscious micro-epochs.

Forebrain recordings, particularly in prefrontal cortex, yielded similar results. These findings demonstrate that both inferotemporal and prefrontal cortex rapidly interleave conscious and suppressed content, suggesting that conscious access requires temporal selection beyond mere localization.