For everyone, a good night’s sleep must be uninterrupted, from falling asleep to the sound of the morning alarm. In reality this is not the case, as also confirmed by a study conducted by the University of Copenhagen, conducted on mice, which recorded up to one hundred nocturnal micro-awakenings. And he came to the conclusion that they are not only normal but also an indication of restful sleep and a great benefit for memory consolidation.
What happens during sleep
According to the researchers, the micro-awakenings are caused by norepinephrine, a stress hormone associated with the “fight or flight” mechanism, which helps to stay focused and is always active during the waking hours. But not only.
“We have seen that norepinephrine can cause up to one hundred nocturnal micro-awakenings, which are not true awakenings. Neurologically, you are awake because your brain activity is the same as during the day, but these moments are so short. that the person doesn’t even notice it, “he explained Mia Andersenone of the authors of the study.
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Precisely these few waking seconds were associated with a memory boost and the consolidation of the day’s memories: “It’s like a reset of the brain preparing to put other memories aside when it goes back to sleep, “he adds Maiken Nedergaardlead author of the research.
I study
The researchers inserted microscopic optical fibers into the brains of some mice, then measured the levels of norepinephrine while the animals slept by comparing them to the electrical activity of the brain. This is how they observed the waves of the neurotransmitter, which was steadily rising and falling every 30 seconds or so. A high level corresponded to a micro awakening.
The mice that had the longest micro-awakenings had fewer memory difficulties. During the day the mice had been made to smell two identical objects. After the hours of sleep, as soon as they woke up, they were brought in front of the objects, but one was different from the previous one. Mice with the longest micro-awakenings were more likely to study the new object, remembering that it wasn’t there the day before.
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A still unclear mechanism
“It is known that the longest micro awakenings occur after a deeper and more consolidated sleep phase. But is the benefit to memory really brought by awakenings? Or rather by the previous good sleep?” We still do not know for sure – he points out. Luigi Ferini Strambi, neurologist, director of the Sleep Medicine Center of the Irccs San Raffaele hospital in Milan -. However, it is well established that these very brief awakenings are normal and are of benefit to the memory strengthening mechanism. The study also confirms that sleep is a dynamic condition and not a static one, as is thought. And there is not only norepinephrine, also acetylcholine, for example, another neurotransmitter, is activated in certain stages of sleep “.
The good awakenings
It happens to be distressed by nocturnal awakenings, especially if you suffer from insomnia, but according to Ferini Strambi, too much negative emphasis is placed on this aspect: “You don’t need to worry about 3-4 short awakenings perceived during the night, our mind is very concentrated more about these than about all the hours of sleep that actually occurred. Small awakenings are normal, they are part of the sleeping microstructure (cycling alternative pattern), which includes oscillations during the night. The awakenings, as we have seen, are positive. Even in the elderly, for example, in which they can prevent nocturnal asystoles caused by excessive rigidity of the vagal system “.
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But if it is the heat that interrupts sleep or street noise or any other external agent and if you stay with your eyes open for a long time, then we can no longer speak of micro-awakenings but of actual sleep interruption, far from it. how beneficial.