Feb 06, 2022 15:00:00

Possibility that the brain can distinguish 'voice of a person who knows and voice of a person who does not know' even if it is asleep

Recent developments in sleep science have shown

that the human brain monitors its surroundings through auditory stimuli even while sleeping. On the other hand, if you wake up with harmless sounds such as the voice of a roommate or the sound of rain, you will not be able to get enough sleep, so the brain will make 'sounds that should wake up' and 'sounds that do not have to wake up' in some way. It is believed to be identifying. Experiments conducted by Austrian and Swiss research teams have shown the possibility that 'the sleeping brain distinguishes between'the voice of a person who knows'and'the voice of a stranger'.' rice field.

The brain selectively tunes to unfamiliar voices during sleep | Journal of Neuroscience
https://www.jneurosci.org/content/early/2022/01/06/JNEUROSCI.2524-20.2021

How the brain tunes in to unfamiliar voices while you're sleeping – and why it matters
https://theconversation.com/how-the-brain-tunes-in-to-unfamiliar-voices-while-youre-sleeping-and-why-it-matters-175018

A research team led by researchers at the University of Salzburg, Austria, recruited 17 subjects to sleep overnight in the laboratory and conducted an experiment to record brain waves during sleep. In this experiment, the research team repeatedly played back various audio data at a volume that did not wake up the sleeping subject.

The reproduced voice data was a recording of 'a voice that reads out the subject's name and other names.' There were various voices that read the name aloud, including the voices of familiar people such as the subject's parents and partners, and the voices of others who were unfamiliar with it.

The research team, which analyzed the reaction of the brain to the voices of familiar and unfamiliar people, found that the reactions of '

K compound wave ' and 'micro-awakening' change depending on the degree of familiarity with the voice. discovered. The K complex wave is a type of brain wave seen during sleep, which occurs when the perceived external stimulus is likely to be harmless, and is thought to play a role in preventing awakening.

From the analysis results of the records, it was found that more K-complex waves are generated when an unfamiliar voice is heard than when a familiar voice is heard. The researchers argue that unfamiliar voices are more likely to awaken humans, so the brain may emit more K-complex waves to avoid awakening the body. increase. Interestingly, the difference between the familiar and unfamiliar K complex waves disappeared in the second half of the night. This may be the result of the brain learning that the voice is safe.

We also found that unfamiliar voices also cause more micro-awakening than familiar voices. Micro-awakening is an activity that appears as a brain wave that is a mixture of wakefulness and sleep, and although it lasts for a few seconds, it usually does not wake up. At this time, it seems that the function of micro-awakening is unknown, but it has been pointed out that it may play a role in processing information from the environment to determine whether it is harmful or not.

Although this study was small, it provides evidence to reinforce the theory that the human brain monitors surrounding events even when it falls asleep and determines whether it is dangerous to receive information. It is what we provide. The research team points out that the tendency for familiar voices to be considered safe is also an evolutionary advantage, while it can be a clue to danger if the voice is unfamiliar. However, it is difficult to prove that 'the brain is judging whether it is dangerous' just because K compound waves and micro-awakening increase in response to unfamiliar voices.

'If you're having trouble sleeping in a new environment, such as a hotel room, you already know why. A duck that sleeps with one eye open,' said

Jakke Tamminen , a psychology instructor at the Royal Holloway University of London. So, your sleeping brain is busy getting used to the new environment, generating more K complex waves and micro-awakening than usual, but at the same time learning about the environment and being able to adapt quickly. Press the stop button on the podcast or TV show to help your brain and fall asleep in silence. '