Brain May Be Switching Between 2 Realities 15 Times A Second, Study Suggests

Your brain may be doing something surprising even when you think you are seeing the world clearly. It could be rapidly switching between information you are consciously aware of and visual information that remains outside your awareness, according to a new study. The research, which involved macaque monkeys and human volunteers, suggests that brain activity alternates between representing a face that is consciously seen and another that is suppressed from awareness around 15 times a second. The findings could offer new clues to one of neuroscience's biggest puzzles: How the brain decides what enters our conscious experience.

The study, titled 'Rapid Alternation Of Conscious And Suppressed Stimulus Representations In The Primate Brain', was led by neuroscientists Janis Hesse and Doris Tsao of the University of California, Berkeley. It has been published as a preprint and has not yet undergone peer review.

How Did The Researchers Study The Brain?

The team demonstrated a phenomenon known as binocular flash suppression. In this experiment, each eye is shown a different image. When a second image suddenly appears before one eye, it typically becomes the one a person consciously sees, while the first image remains visible to the eye but disappears from awareness.

The researchers first tested this effect on 14 human volunteers to confirm that the newly introduced image dominated what they reported seeing.

They then used electrodes to record the activity of large groups of neurons in two macaque monkeys as the animals viewed competing images of faces. The recordings focused on brain regions involved in recognising faces and processing information, including parts of the visual cortex and prefrontal cortex.

What Did The Study Find?

Although the monkeys were presented with two competing faces, their brain activity did not continuously represent only the face that was expected to dominate conscious perception.

Instead, the researchers found that neural activity rapidly alternated between patterns representing the face that was consciously seen and the face that was suppressed from awareness. This happened around 15 times a second, even when the consciously perceived image remained unchanged.

In simple terms, the brain appeared to keep representing information about both images, switching rapidly between them in its neural activity.

The researchers could even reconstruct the two faces from these different patterns of brain activity. The representation of the consciously seen face was more sharply tuned to its features during the corresponding periods.

Does This Mean We Experience Two Realities?

The findings do not mean people consciously experience two different realities or that their awareness switches on and off 15 times every second. Instead, they suggest that information outside conscious awareness may continue to be represented in the brain, even when another image dominates what we see.

The researchers believe studying these rapid changes could help explain why some information reaches awareness while other information remains hidden from it.

However, the findings are preliminary. The recordings were made in just two monkeys, and the study examined specific brain regions rather than the entire brain. The human volunteers helped verify the visual illusion; they were not the subjects of the same neural recordings.

The work, therefore, offers a possible new way of understanding how the brain processes conscious and unconscious visual information, rather than a definitive explanation of consciousness itself.