A hidden brain rhythm challenges ideas about where consciousness comes from

by Paul Arnold, Medical Xpress

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How our brains give rise to consciousness is one of the biggest mysteries in neuroscience. But new research by Janis Hesse at the University of California, Berkeley, and colleagues, may help fill in some of the details. The insights are coming from studies on macaque monkeys.

For years, neuroscientists have been divided over whether the neural mechanisms underlying consciousness lie primarily in the front or the back of the brain. Some researchers champion frontal regions through frameworks like global neuronal workspace and higher-order models. Others support posterior zones through models like integrated information theory and recurrent processing.

This new study suggests both camps might be arguing about the wrong thing.

Probing consciousness

To figure out what the brain is doing during conscious perception, the team needed a way to control what the monkeys could see and what remained hidden from their awareness.

They used a technique called binocular flash suppression, in which an image shown to one eye disappears from conscious awareness when a different image is flashed to the other eye. They tested it on 14 adult humans and, after demonstrating it worked, applied the same approach to macaque monkeys.

First, the researchers showed two macaque monkeys a series of pictures, including faces and other objects, while the animals kept their eyes fixed on a small dot in the center of the screen. The monkeys received a juice reward for maintaining their gaze on the dot.

Once they learned to keep their eyes fixed on the dot, the main experiment began.

The team flashed a new image into one eye to make it dominate perception, while the original image was expected to remain hidden from awareness. The monkeys kept looking at the dot as neural probes recorded activity from hundreds of individual brain cells at once.

An unexpected pattern

The findings, reported in a paper posted on the bioRxiv preprint server, revealed a curious pattern. The probes picked up a rapid rhythm in the brain. Roughly 15 times every second, brain cells switched between responding to the picture the monkeys could see and the one hidden from their awareness.

"These findings show that time provides a critical dimension for separating conscious and suppressed representations within cortical population activity," the study authors write.

These rapid shifts were not confined to a single area. Researchers found similar patterns in regions toward both the front and back of the brain. This suggests that when it comes to conscious vision, when brain cells are active may be just as important as where they are located.

"Our findings expose a limitation of searching for the neural correlates of consciousness within the average activity of specific brain regions, whether toward the front or back of the brain," the authors write.

Written for you by our author Paul Arnold, edited by Sadie Harley, and fact-checked and reviewed by Robert Egan—this article is the result of careful human work. We rely on readers like you to keep independent science journalism alive. If this reporting matters to you, please consider a donation (especially monthly). You'll get an ad-free account as a thank-you.

Publication details

Janis K. Hesse et al., Rapid alternation of conscious and suppressed stimulus representations in the primate brain, bioRxiv (2026). DOI: 10.64898/2026.10.15.759299

Journal information: bioRxiv

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Neurology Who's behind this story?

Paul Arnold

BSc Biology from University of London. BBC documentary producer with world travel experience. Freelances from southern Spain. Full profile →

Sadie Harley

BSc Life Sciences & Ecology. Microbiology lab background with pharmaceutical news experience in oil, gas, and renewable industries. Full profile →

Robert Egan

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