psychological, on the other hand they can be deleterious especially for the quality of sleep.
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(EEG).
Using these techniques, the researchers identified two distinct stages of sleep, each characterized by specific physiological changes:
- Slow wave sleep or non-REM sleep (NREM): constitutes about 75-80% of the total sleep time in adults; consists of 4 stages characterized by an increase in the depth of sleep. During non-REM sleep, the brain emits low-frequency electrical waves (in wakefulness, brain waves are fast and erratic). Muscle tone has decreased, but involuntary motor activities occur occasionally (when, for example, changing position in bed). Pressure, temperature and heart rate also decrease. During slow wave sleep a person may think and dream, but thoughts are more logical and with less emotional content than those that occur during REM sleep. Dreams are poorly detailed and often include feelings and vague images.
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- REM sleep (from English Rapid Eye Movement): follows each NREM sleep cycle (note: sleep phases do not occur once a night, but alternate several times for a total of 5-6 complete cycles lasting 90-100 minutes). This phase is characterized by high-frequency electroencephalographic waves and episodes of rapid eye movements under the closed eyelids. The postural muscles lose tone, however the muscles that control the face, eyes and distal leg frequently become phasic. REM sleep is approximately 20% of the total rest time. Compared to slow wave sleep, in this period there is an increase in brain activity except in the limbic system, where, on the contrary, neuronal activity decreases. It is at this stage that dream activity occurs: dreams are more elaborate and intense and are generally very articulate. In REM sleep, thoughts are more illogical and bizarre than in slow wave sleep.
