Does the brain perceive external sounds while sleeping and dreaming?

Scientists from the French National Centre for Scientific Research (CNRS), ENS-PSL, and Monash University in Australia have demonstrated that the brain can suppress information from the outside world, such as conversational sounds during sleep that are associated with dreams. This ability is one of the protective mechanisms of dreaming.

This study was conducted in collaboration with the sleep center of a hospital in Paris.Center du Sommeil and de la Vigilance, The study, conducted at Hôtel-Dieu, AP-HP – Université de Paris, was published in the May 14, 2020 issue of the journal Current Biology.

While we dream, we create worlds that have no relation to the tranquility of our bedroom. In fact, it's quite unusual for environmental factors to be incorporated into dreams. This helps to understand more easily how the brain can protect itself from external influences.

Researchers invited 18 volunteers and had them take a morning nap in a laboratory. Morning naps are often filled with dreams, most notably the dream phase known as "rapid eye movement sleep" (REM sleep).REM sleepThis is because the brain is in a state of alertness during sleep, demonstrating brain activity similar to that of a waking person.

Conversely, the body becomes temporarily paralyzed, though not completely, and during some periods of REM sleep, the eyes still move. Research has shown that this movement is associated with dreaming.

To study how the brain interacts with external sounds during dreaming, scientists had volunteers listen to stories in French and a meaningless language, and then analyzed their brain activity using electroencephalograms (EEGs) and a computer system.

Scientists confirm that even when the brain is sleeping, it still records everything that is happening around it. Furthermore, research shows that during sleep...Light sleep The brain prioritizes speech just as it does when awake.

However, such spoken words are filtered out during REM sleep. That is, the brain during sleep can selectively select information from the outside world and flexibly amplify or enhance details, or even suppress information, depending on whether that information is deeply embedded in the dream.

The research team believes this mechanism can help the brain protect the dream phase, which is essential for emotional balance and the consolidation of the day's learning. Although dreams are prominent during periods of eye movement, they can also occur at various stages of sleep, raising the question of whether these dreams are accompanied by a suppression of the external world.

Translated from the article: The dreaming brain tunes out the outside world
By Ms. Benjarat Rattanachak, Sleep Technician, NK Sleepcare Co., Ltd.
refer: The dreaming brain tunes out the outside world