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What happens in our brain during sleep

It’s really nice to stay under the blankets on cold winter mornings. It isn’t even bad to fall asleep lulled by the cool breeze of spring evenings. Many like to sleep, to have time and not be forced to set the alarm and enjoy sleep. Others, on the other hand, would prefer to use all those hours spent in bed differently.

What does our brain think about sleeping? What happens while we rest? On a normal night, our sleep can be divided into two types: REM sleep (rapid eye movement, due to the rapid eye movements below our eyelids) and non-REM sleep.

In turn, this second type is divided into four other phases. Here is a brief overview to better understand the mechanisms of our brain during rest.

The phases of sleep

Phase 1: drowsiness

This phase begins gradually as we go to bed. It lasts between 30 seconds and 7 minutes. The muscles relax and our brain emits irregular and rapid waves.

Phase 2: real sleep

In this phase we spend about 20% of the night and the brain waves become wider. It can happen to have fragmented thoughts or images, however we are unconscious to everything surrounding us; even if our eyes were open, we would see nothing.

Phases 3 and 4: deep sleep / delta sleep

This period takes up about 50% of the rest. Describing the waves produced by the brain, they now become slow and even wider. In these phases it is very difficult to wake up because the blood is sprayed to the muscles.

Phases 3 and 4 allow the body to rest and regenerate itself and, in young people, to grow. If you didn’t go through the deep phases of delta sleep, the person would feel tired, apathetic or even depressed the following day.

Delta sleep helps young people to grow

REM phase

It repeats cyclically every 90 minutes and increases its duration as it recurs during the night. The brain returns to work hard: the blood flows in greater quantities and the waves correspond almost to those of when we are awake. It is at this stage that we dream.

Despite all this activity, we can’t move our muscles, and this prevents us from acting in reality based on what we visualize in our mind, so we can’t hurt anyone.

REM sleep cycles are essential for our mental well-being: the brain scans everything we have stored in short-term memory, analyzes it, discards unimportant data, and stores others in long-term memory.

If we don’t go through enough cycles of REM sleep, emotional problems may arise, in fact insomnia causes dangerous spirals of growing anxiety.

Polyphasic sleep

A question arises concerning our sleep: what would happen if by choice or necessity we regularly deprived ourselves of these cycles? The experts believe that is required a good sleep of about 8 hours per 24.

If we sleep fewer consecutive hours than necessary we cannot benefit enough from the last and longest cycle of essential REM sleep.

The polyphasic sleep, which with different methods leads to reduce the amount of time spent sleeping at 5 hours and 20 minutes, 4 hours and a half or even just 2 hours, often does not allow to arrive at delta sleep and its benefits listed above.

It could therefore cause a reduction in attention and mental clarity, to suffer from memory lapses, difficulties in expressing and being less creative.


It is not a matter of wasted time, but of time invested for the well-being of ourselves. Having more hours available, but with reduced capacity due to sleep debts would probably be counterproductive. Better to pay attention to the quality of our resources than simply to their quantity.

This post is also available in: Italiano

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