We wake up 100 times every night, and this is good for memory!
- On average, an adult should sleep 7.5 hours, or five cycles of 1.5 hours each. At an average of 6h45 per night, according to Public Health France, the French today are a little off target.
- “Good night,” according to the National Institute of Health and Medical Research, averages 4 to 6 consecutive cycles of 90 minutes. Each cycle consists of three distinct phases: light slow-wave sleep, deep slow-wave sleep, and REM sleep.
A good night’s sleep doesn’t have to mean a linear, uninterrupted sleep. Moreover, seven or eight hours of sleep at once, this does not exist!
“We wake up more than a hundred times a night, and that’s during perfectly normal sleep,” says Silla Kirby, co-author of a book by Danish scientists recently published in the scientific journal Nature.
small alarm clocks
We are not talking here about insomnia or specific sleep disturbances that require potential medical follow-up, but about small wakes or wakes, which are common to all mammals.
To reach these conclusions, researchers from the University of Copenhagen (Denmark) studied the sleep of mice using microscopic sensors and fiber optics. Thus, they noticed that the brain of rodents “wakes up” more than 100 times a night, but in such a short time the sleepers do not realize it and immediately fall back to sleep.
It’s the same with humans: the sleeper does not wake up, strictly speaking, every time – which is why he does not remember – but his brain activity is recovering. Well on the way. Maiken Nedergaard, who led the research, explains: “You could say that short awakenings reset the brain so that it is ready to store the memory when you go back to sleep.”
The reason for these hundreds of nocturnal awakenings? The researchers explained that noradrenaline, a stress hormone and neurotransmitter linked to adrenaline. When we sleep, the level of norepinephrine in the blood rises and falls every 30 seconds, according to a wave pattern. If it is high, it means that you are awake for a while, if it is low, then you are asleep. It is the fluctuation of norepinephrine levels that makes partial awakening possible.
In parallel, the study revealed that the more the level of norepinephrine changed during sleep, the better the memory afterwards. “mice [ayant les plus hauts niveaux de variation de noradrénaline] She developed a “supermemory”. They had less difficulty remembering the things they had learned the night before. This suggests that the dynamics of norepinephrine enhance sleep processes that affect our memory.
And as a reminder, these little awakenings aren’t a sleep disorder per se: they only become one if you don’t go back to sleep afterwards. In the event of chronic fatigue, frequent drowsiness, or persistent difficulty concentrating, a medical consultation is recommended. In France, more than one in three adults say they suffer from at least one sleep disorder (insomnia, apnea, etc.).