Sleep is a physiological state that allows the body to rest, to recover from a physical point of view but also psychic, and to improve our memory (sleep helps indeed - between others - to strengthen our memory and make it more accessible the next day).
As a general rule, a night's sleep includes several sleep cycles.
During our sleep, the state of consciousness and the functions of our body are modified. A person who sleeps is less responsive to external stimulation than when he is awake ... but can still be awake (as opposed to a profound loss of consciousness, or a coma).
In a sleep center, one can track and analyze a person's sleep and cycles, record brain flows and graphically represent them using an electroencephalogram (EEG) : the shape of the curves collected by different electrodes, provides information on the depth of sleep and sleep cycles that the sleeper goes through at any given moment. Other tests performed in a sleep center, allow to analyze the sleep and its quality.
Regardless of the length of sleep - which varies from person to person - the sleep pattern in different sleep cycles is almost identical for everyone (for all "normal" sleepers). The doctors distinguish the:
- Non-REM sleep which is in turn divided into 3 phases, and
- REM sleep (which corresponds to paradoxical sleep)
The 4 phases of sleep (REM sleep and 3 non-REM sleep phases) are repeated several times a night, thus forming sleep cycles.
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Read also :
> Hypnosis to sleep
Authors: Dorothee Gebele, Dr. Nicolas Evrard