Mammals are 'micro-awakened' more than 100 times during sleep but are unaware

The memory of 'wake up during sleep' is usually not remembered except when waking up to go to the bathroom. However, a study in mice conducted by the University of Copenhagen showed that from a neurological point of view, mammals may wake up more than 100 times a night.

Memory-enhancing properties of sleep depend on the oscillatory amplitude of norepinephrine | Nature Neuroscience
https://doi.org/10.1038/s41593-022-01102-9

Stress transmitter wakes your brain more than 100 times a night – and it is perfectly normal – University of Copenhagen
https://healthsciences.ku.dk/newsfaculty-news/2022/07/stress-transmitter-wakes-you-up-more-than-100-times-a-night--and-it-is-perfectly-normal / /

The research team measured noradrenaline production in sleeping mice. Noradrenaline is a hormone whose secretion is known to decrease during sleep, and it is possible to determine neurologically whether or not you are sleeping by measuring the amount of secretion.

As a result of the measurement, it was found that the amount of noradrenaline secreted in sleeping mice frequently increased and decreased. The amount of noradrenaline increased more than 100 times during one sleep, and the amount of secretion when it increased was equivalent to the amount of secretion at the time of waking up, so the research team said, 'Neurologically, sleep. The mice inside have been awakened more than 100 times. '

Since the time when noradrenaline secretion increased was momentary, the research team said, 'Every 100 awakenings are momentary, so you do not notice that you are awake.' In addition, this measurement of noradrenaline secretion was performed in mice, but since the relationship between sleep and noradrenaline secretion is a common mechanism in mammals, similar 'microawakening' occurs in humans. The research team speculates.

In addition, the research team conducted an experiment to investigate the effect of mouse sleep patterns on memory, 'giving two objects to mice before sleep, and giving one of the two objects to another after waking up'. I did it. As a result, the mice with a larger decrease in noradrenaline secretion showed an interest in the object given for the first time after waking up. Since mice with a large decrease in noradrenaline secretion can recognize 'objects different from those before sleep', the research team considers that increasing or decreasing noradrenaline enhances 'the effect of sleep on memory'.

According to the research team, some antidepressants increase the amount of noradrenaline secreted. The researchers point out that drugs that increase noradrenaline production can have a negative effect on memory if the reduction in noradrenaline production during sleep is reduced. 'It may be necessary to look at the types of drugs that change the level of noradrenaline in the body and develop drugs that do not affect the amount of noradrenaline secreted in the future,' he said.