Researchers were surprised to find that the brain's response to sound remained strong throughout sleep.
This means that during sleep, the brain analyzes sound signals, but cannot focus on the sound or identify it, and therefore it does not wake up.
The researchers placed at the bedside of patientsspeakers making different sounds and compared the data from the electrodes he implanted. The latter studied neural activity and electrical waves in different areas of the brain, this happened during wakefulness and at various stages of sleep. In total, the team collected data from more than 700 neurons, about 50 neurons per patient, over a period of 8 years.
According to the authors, until recentlyit was believed that during sleep, all sound signals quickly fade away as soon as they reach the cerebral cortex. But when they looked at the data from the electrodes, they were surprised to find that the brain's response during sleep was much stronger and richer than expected. Moreover, this powerful reaction spread to many areas of the cerebral cortex.
Researchers explain that alpha-beta waves (10-30 Hz) are associated with attention and anticipation processes, and are controlled by feedback from higher areas of the brain.
The authors believe that their study providesclue to the age-old question: what is consciousness? The brain activity that defines consciousness allows people to be aware of what is going on around them, but disappears during sleep.
In this study, the scientists found a new clue, and they are going to continue to study the mechanisms responsible for this difference.
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