While you sleep , not everything is at rest ; the brain, for its part, carries out more or less intense activity. This depends on the sleep phase it enters; these different phases form what is called the sleep cycle.
What is a sleep cycle?
It is impossible to talk about sleep without referring to the concept of the sleep cycle , as it is fundamental to the subject. Thus, it is defined as the combination of two different types of sleep to form a single whole.
These 2 types of sleep are identical each time and follow a precise order; they are called the sleep phases.
Therefore, an adult's sleep is characterized by two main stages. The first stage is called slow-wave sleep , and it always precedes the second stage, which is called REM sleep .
Thus, a typical night can have between 3 and seven cycles, and each stage of the cycle lasts about 1 to 1.5 hours. However, during the night, the duration of slow-wave sleep decreases at the expense of that of REM sleep.
What can we learn from the two phases of the sleep cycle?
As mentioned earlier, the sleep cycle is subdivided into two phases: slow-wave sleep and REM sleep. Slow-wave sleep is the phase that automatically follows falling asleep .
During this phase, even if the brain is not as active as upon waking , it is still engaged in activity. Certain areas, such as the medial prefrontal cortex, help to strengthen memory .
As for the second phase, which is REM sleep; it promotes the activity of areas that play an essential role in the development of our emotions.
These areas are the amygdala, the anterior cingulate gyrus (for emotions), and the temporo-occipital cortex, which processes visual information. This explains the vividness of dreams and the emotions we experience within them.
