Behavioral and electrophysiological evidence for fast emergence of visual consciousness

People can report whether they consciously saw a visual stimulus in just over 200 milliseconds, and these reports are extremely reliable and not reflexive or unconscious. The neural events that cause conscious vision must happen before these reports. Late cortical processing in the fronto-parietal global neuronal workspace, which occurs around 300 milliseconds, starts after the fastest consciousness reports, so this late activity cannot directly reflect the emergence of visual consciousness. Instead, a negative amplitude difference spreading from occipital to frontal cortex around 160–220 milliseconds precedes the reports, suggesting this neural correlate underlies the emergence of conscious vision.

Study at a glance

Abstract

Abstract A fundamental unsettled dispute concerns how fast the brain generates subjective visual experiences. Both early visual cortical activation and later activity in fronto-parietal global neuronal workspace correlate with conscious vision, but resolving which of the correlates causally triggers conscious vision has proved a methodological impasse. We show that participants can report whether or not they consciously perceived a stimulus in just over 200 ms. These fast consciousness reports were extremely reliable, and did not include reflexive, unconscious responses. The neural events that causally generate conscious vision must have occurred before these behavioral reports. Analyses on single-trial neural correlates of consciousness revealed that the late cortical processing in fronto-parietal global neuronal workspace (∼300 ms) started after the fastest consciousness reports, ruling out the possibility that this late activity directly reflects the emergence of visual consciousness. The consciousness reports were preceded by a negative amplitude difference (∼160–220 ms) that spread from occipital to frontal cortex, suggesting that this correlate underlies the emergence of conscious vision.