Researchers at the University of California, Berkeley, led by Yannis Hesse, have discovered a rapid, hidden electrical cycle in the brain that challenges fundamental theories about the origins of consciousness.
For decades, neuroscientists have been trying to determine exactly how the brain generates consciousness. Specialists are divided into two camps: some believe that the mechanisms of consciousness are controlled by the brain’s frontal lobe. Others rely on the Integrated Information Theory and recurrent processing models, assigning the leading role to the brain’s posterior regions. However, according to a new study published on the bioRxiv platform, both sides may be wrong because they focus exclusively on spatial location while overlooking a crucial factor: time.
To investigate what the brain does at the precise moment of conscious perception, the scientists separated consciously perceived information from subliminal information. They used a technique known as binocular rivalry suppression: when a new, vivid image is presented to one eye, the original image shown to the other eye disappears from conscious awareness, even though the brain continues to process it. The researchers initially tested the technique on 14 adults and, after confirming its effectiveness, proceeded with experiments on macaques.
In the first stage, the scientists trained two macaques to maintain their gaze on a small dot in the centre of a screen, rewarding them with fruit juice to keep them motivated. They then showed the animals images of faces and various objects. During the main experiment, a new image was suddenly presented to one eye, gaining perceptual dominance and pushing the previous image out of conscious awareness. Using specialized neural probes, the researchers simultaneously recorded the activity of hundreds of individual neurons during this process.
The resulting data revealed an unexpected pattern: brain cells switched their activity between the consciously visible and suppressed images approximately 15 times per second (at a frequency of 15 hertz). The scientists detected this rapid alternation of neural signals not in a single isolated region, but simultaneously in both the frontal and posterior regions of the brain.
The authors explain that neurons in the cerebral cortex distinguish between conscious and suppressed (subliminal) information based on timing. Accordingly, the precise moment when neurons become active is just as important for conscious vision as their anatomical location. The findings demonstrate that searching for the neural basis of consciousness by observing only the average activity of specific brain regions is unlikely to yield meaningful results.
