If you wake up 100 times every night, can you still say you slept well?

Late at night, you wake up from sleep, and the alarm shows 2:56. Waking up at this time means that you have to drink a lot of coffee to stay awake tomorrow morning. The reason why waking up in the middle of the night is very annoying is that most of us believe that high-quality sleep should be undisturbed and last until dawn.

However, a new study from the University of Copenhagen shows that norepinephrine, a stress sensor, can wake you up multiple times a night - but don't worry, this is perfectly normal. Norepinephrine is a stress hormone and transmitter substance related to adrenaline, which is involved in the body's fight or flight response. Norepinephrine increases in stressful situations and also helps to keep you focused .

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Many people think of sleep as a continuous state - either asleep or awake, but there is actually more to sleep than meets the eye. Norepinephrine can cause a person to be awakened more than 100 times a night, but this happens during completely normal sleep. Although technically the brain is awakened because during these very brief moments the brain's activity behaves in the same way as when awake, this is not true wakefulness because the moment is so brief that the person sleeping does not even notice it.

There's more to sleep than meets the eye | Giphy

The researchers conducted experiments in mice and believe that this discovery may be further translated to human studies because they focused on basic biological mechanisms - mechanisms that are common to all mammals. This new discovery helps us understand what is happening in the brain during sleep.

Researchers have found that very brief awakenings during sleep, caused by fluctuations in norepinephrine, are also important for memory. These brief awakenings reset the brain so that when you go back to sleep, it's ready to store memories.

The researchers inserted a microscopic optical fiber made of glass and genetically manipulated "light receptors" into the brains of test mice and connected the fiber and LED light source to a cable. They measured the norepinephrine levels of these mice while they slept and compared them with the electrical activity in the brain. The researchers then used the implanted device to increase the amplitude of norepinephrine fluctuations and improve the animals' memory.

Previous studies have shown that norepinephrine is associated with stress and is inactive during sleep. However, this new study shows that when we sleep, the level of norepinephrine in the body increases and decreases in waves. High levels of norepinephrine mean that the brain is in a short state of wakefulness, while low levels of norepinephrine mean it is in a state of sleep. In other words, norepinephrine levels and the degree of "wakefulness" are interconnected and constantly changing.

The two most awake peaks were about 30 seconds apart, and the deeper the trough, the better the sleep. The higher the subsequent peak, the higher the awakening. This suggests that even if you wake up in the middle of the night, you don't have to worry too much. Of course, long periods of insomnia are not good, but the study shows that short awakenings are a natural part of the sleep stage related to memory, which may even mean that you slept well.

Short awakenings are a natural part of the sleep phase associated with memory, and may even mean you slept well.

Sleep is good for us in many ways - it removes waste products, protects against Alzheimer's disease and improves our memory, the latter of which was the focus of the study. The results showed that the mice with the most troughs in norepinephrine levels also had the best memories.

During the experiment, mice first sniffed two identical objects and then went to sleep. After waking up, the mice were re-exposed to the previous study object, however, one of the two objects had been replaced by a new one. Mice with more norepinephrine troughs during sleep were more likely to be curious about the new object, indicating that they remembered that it was different from the last object they saw.

In addition to increasing our understanding of sleep mechanisms, the new research also provides ideas for the research of antidepressant drugs.

Some forms of antidepressant medication increase norepinephrine levels in the body, making it easier to reduce deep sleep. This work suggests that this may also affect memory. Scientists will continue to look at how different types of drugs regulate norepinephrine levels in the body and focus on developing drugs that do not affect norepinephrine fluctuations during sleep.

From I am a scientist iScientist, author Future Light Cone Accelerator

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