Researchers at France’s ENS Paris1 and CNRS, in collaboration with Monash University in Australia, have discovered that the brain is capable of tracking sounds in its environment and favouring the most relevant sounds while we are asleep.
The study, published in Nature Human Behaviour, reveals that the brain has the ability to process and filter sounds while we are sleeping. This explains, for example, why when you snooze on the commute, you always seem to wake up right at your stop.
Previous studies have shown that certain sounds are perceived more easily during sleep. To wake someone up, for example, saying their first name has more impact than saying the name of another person. However, these studies focused on isolated sounds.
The authors of this new study decided to focus on the brain’s reaction to a multitude of sounds during sleep. This is more representative of reality, especially for city dwellers, who are exposed to a variety of sounds during their sleep.
In this study, 24 participants were exposed — during their sleep — to two voices with highly similar acoustic properties but saying radically different things. One was reading excerpts from films and articles, while the other pronounced a flow of words resembling language but devoid of meaning.
The scientists analyzed brain activity using a technique that can reconstruct what the sleepers hear. Based on their findings, the researchers were able to confirm that during light sleep, participants favoured the message that held meaning for them.