Why the brain may not respond to sounds during sleep - study

A study by the Universities of Lausanne and Geneva involving 25 volunteers showed that during sleep, the brain reduces its response to external sounds, especially during phasic REM sleep, but maintains a high response to its own heartbeat. This explains why a person may not wake up even from a loud noise.

Scientists from the Universities of Lausanne and Geneva conducted a study with 25 volunteers to understand how the brain responds to sound signals during sleep. Using electroencephalography, they compared the response to external sounds with the response to the rhythm of one's own heartbeat. The results showed that during the transition from wakefulness to the rapid eye movement (REM) phase, sensitivity to external sounds gradually decreases, especially during phasic REM sleep, when rapid eye movements and the most vivid dreams occur. At the same time, the response to one's own heartbeat remained high throughout the night and was even stronger than during wakefulness. The researchers explain this by the fact that during sleep, the brain redistributes attention from external stimuli to monitoring internal bodily processes. Therefore, a person may not wake up even from a loud noise. Earlier, Kursor reported that the brain can simulate future events during sleep.