The neurotransmitter norepinephrine causes the brain wakes up more than 100 times a nightand, according to new research from the University of Copenhagen (Denmark), which points out that this “is perfectly normal and may even indicate that you have slept well”.
“Most people believe that a good night’s sleep should not be uninterrupted. You may think of sleep as a constant state that you are in and then wake up. But the dream is much more than it seems. We have learned that norepinephrine causes you to wake up more than 100 times a night. Cast during perfectly normal sleep“, explains Celia Kjaerby, one of the first authors of the study, which has been published in the scientific journal ‘Nature Neuroscience‘.
Although norepinephrine technically causes the brain to wake up more than 100 times a night, we don’t think of it as waking up. “Neurologically, you do wake up, because your brain activity during these very brief moments is the same as when you’re awake. But the moment it is so brief that the sleeper does not realize“, details Mie Andersen, second first author of the study.
Although the researchers have studied mice, their findings can most likely be transferred to humans, because they have focused on basic biological mechanisms, that is, mechanisms that are shared by all mammals.
“It allows us to remember what we learned”
Professor Maiken Nedergaard, who led the study, considers the new finding to be a important piece of the puzzle to understand what happens in the brain when we sleep.
“We have found the essence of the part of the dream that makes us wake up rested and that allows us to remember what we have learned the day before. We have found that the refreshing part of sleep is powered by waves of norepinephrine. Very short arousals are created by waves of norepinephrine, which are also so important for memory. It could be said that the brief awakenings reset the brain so that it is prepared to store the memory when it goes back to sleep”, says the researcher.
Previous research has suggested that norepinephrine, associated with stress, is inactive during sleep. So the researchers were surprised to see how active norepinephrine actually is during sleep.
This new study shows that when we sleep, the level of norepinephrine in the body constantly rises and falls in a wave-like pattern. High levels of norepinephrine mean that the brain is briefly awake, while low levels of norepinephrine mean that it is asleep. That is, norepinephrine levels and the degree of “arousal” are connected and constantly changing.
no need to worry
“It takes about 30 seconds from one ‘top’ to another, which means your norepinephrine levels are constantly changing. At the same time, we were able to see that the more deep is the ‘valley’, that is, the better one sleeps, the higher the next ‘top’ and the greater the degree of awakening,” says Mie Andersen.
“This shows that you may not have to worry if you wake up at night. Of course, it’s not good to be without sleep for long periods, but our study suggests that short-term awakenings are a natural part of sleep-related phases. with memory. It can even mean that you slept very well,” adds Kjaerby.
It is well known that sleep is good for us, in several ways. Eliminate waste products prevents Alzheimer’s and improves our memory.
This last aspect was also the subject of this study, and the results suggest that the mice with the greatest number of deep norepinephrine valleys were also the ones with the best memory.
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“The rats they developed a ‘super memory’. They had less trouble remembering things they had learned the day before. Of course, this suggests that norepinephrine dynamics reinforce sleep processes that affect our memory,” says Kjaerby.
First, the mice were allowed to sniff two identical objects. They were then put to sleep and, once awake, they were returned to the objects. However, one of the two objects had been replaced by a new one. The mice that had experienced the greatest number of norepinephrine troughs were more inclined to study the new objectsuggesting that they remembered seeing a different object the last time.