The boundaries with awakening are more ambiguous than expected

Sleep is usually thought of as a state in which the body and mind are at rest, disconnected from the rest of the world, so to speak. But the boundaries between wakefulness and sleep are blurrier than they seem, French researchers write New study.

They showed that normal people can pick up on verbal information coming to them through a human voice while they sleep. They may respond by tightening their facial muscles in different ways. This remarkable property sometimes appears during each stage of sleep, like a sort of port of communication with the outside world that opens at regular intervals.

1001 forms of consciousness
It may make it possible to develop standard communication protocols with sleeping people, to get a better idea of ​​how mental activity changes during sleep. Communicating with sleep subjects can facilitate understanding of the cognitive processes that underlie normal and disturbed sleep patterns.

“Sleep is a very complex phenomenon, even though it seems very simple and ordinary, because we sleep every night,” says neuroscientist Lionel Nakash. “Our research shows that wakefulness and sleep are not stable states. On the contrary, we can describe them as a mosaic of conscious and unconscious moments.

Sleep disturbances due to balance disorder
In order to improve people’s sleep, it is necessary to know how the brain works in states of wakefulness and sleep. “If we lose balance, it can cause disorders such as sleepwalking, sleep paralysis, hallucinations, and the feeling of not sleeping all night or just sleeping with our eyes open,” says sleep researcher Isabelle Arnulf.

To distinguish between wakefulness and different sleep stages, researchers typically use physiological indicators such as specific brain waves that can be seen in an electroencephalogram (EEG). Unfortunately, these brain movies do not provide a detailed picture of what exactly is going on in a sleeping person’s head. Sometimes they conflict with the testimonials of the person being tested. “We need more accurate measurement tools that confirm the experience of a sleeping person. This way we can better estimate the level of alertness,” says researcher Delphine Audet.

Narcolepsy and rapid eye movement sleep
Therefore, the French team examined 22 people who did not suffer from sleep problems and 27 patients with narcolepsy, or people who regularly sleep uncontrollably during the day. People with narcolepsy often have lucid dreams, in which they are aware that they are asleep. Sometimes they can even direct their dreams and shape their entire dream scenario. During the day, they can easily and quickly enter the suppressive stage of sleep – the stage of sleep in which lucid dreams occur.

Scientists selected narcolepsy patients to investigate the level of consciousness during sleep under experimental conditions. “One of our previous studies has already shown that during lucid REM sleep, it is possible to communicate with dreamers and vice versa. Now we want to know if this is also possible during other sleep stages and in people who are not lucid dreamers.”

Lucid dreaming with a smile and a frown
Participants took a nap in the laboratory, after which they were given a word choice test consisting of real and non-existent spoken words. Subjects had to collect the terms in their sleep through a smile or a frown. At the same time, brain and heart activity, eye movements and muscle tension were measured. After waking up, participants had to report whether they had had a lucid dream and whether they remembered anything from the interaction.

“Most participants responded well to verbal stimuli during sleep, whether they had narcolepsy or not. It turns out that this happens more often during lucid dreaming, where there is a much higher level of awareness. But we also saw communication to a lesser extent in all other stages of sleep.” , whether in people who sleep normally or in patients with narcolepsy.

Accelerate brain activity
By combining all the data, it seems possible to predict the opening of these connected vents. When these “windows are open,” participants can answer the question of whether the word is real or made up. There was a clear acceleration in brain activity and other physical responses associated with higher cognitive activity. “In the case of lucid dreamers, the ability to respond to words was linked to a specific electrophysiological pattern,” explains Discussion.

More research is needed to find out whether the frequency of these interaction periods indicates sleep quality and whether these moments can be used for learning or to treat some sleep disorders. “We hope that the use of advanced neuroimaging techniques will give us a better picture of the brain mechanisms responsible for sleep behavior in the future,” Audet concludes.

Sleep appears to be a more active and conscious state than we always thought, with the sleeper sometimes being distinctly open to the world and the people around him.