EPFL · Wetenschap

Brain Activity Patterns May Distinguish Unconscious Visual Processing from Conscious Perception

EPFL researchers have identified two distinct patterns of brain activity that could differentiate between unconscious visual processing and the formation of a unified conscious perception. This research sheds light on how the brain integrates visual information over time, a process known as "postdiction," where later events can influence the perception of earlier ones.

The study, published in PLOS Biology, utilized the Sequential Metacontrast paradigm (SQM) illusion to investigate this phenomenon. In SQM, participants are presented with rapid visual stimuli, and later stimuli can alter the perception of earlier ones, creating the illusion that conscious vision is an edited, rather than live, feed.

Using electroencephalography (EEG) and machine learning, the EPFL team recorded brain activity in 18 participants. They observed an early pattern of activity in occipital brain areas around 200 milliseconds after visual offsets appeared, which encoded individual events even when they were not consciously distinguishable. A subsequent pattern emerged around 450 milliseconds over central and parietal areas, associated with the integrated offset and participants' conscious reports.

The researchers propose that the transition between these two activity patterns signifies the shift from unconscious encoding to conscious perception. While the later signal might also involve decision-making, this distinction offers a novel method for separating neural activity related to unconscious visual integration from that associated with conscious perception, potentially aiding theories of consciousness and the understanding of coherent visual experience.

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