About every hour and a half, sleepers lapse into a peculiar state: the heart beats faster, breathing rate and blood pressure increase, and the eyes wander back and forth with the eyelids closed – the REM phase has begun. The discovery of REM sleep was only about 50 years ago. The research team led by sleep scientist Nathaniel Kleitmann discovered REM phases in 1953 in a sleep laboratory he set up in Chicago.
NON REM and REM phases
Our sleep is not the same depth throughout the entire time – it occurs in phases that repeat several times during the night. Sleep is divided into five phases, which can be distinguished by brain waves of varying intensity: the NON-REM phases, with stages 1 to 4, and the so-called REM (rapid eye movement) phases, which are characterized by rapid movement of the eyes under the eyelids. While deep sleep is largely credited with physical regeneration, sleep researchers believe that REM sleep is necessary for psychological recovery. To date, sleep researchers are still not in complete agreement about the role of rapid eye movements.
The REM phase
During REM sleep, we have the most and the most intense dreams – which is why this sleep stage is also called the dream phase. Eye movements are particularly strong then, heartbeat, blood pressure and breathing become faster and more irregular, signs of sexual arousal can also be noticed. In the REM phase, the electroencephalogram shows increased activity, but at the same time muscle tone is greatly reduced. This process is actively controlled by our brain. Without the reduced muscle tone, the sleeper would actually perform all the dreamed movements, which would of course be fatal. Those who are awakened from REM sleep can remember their dreams particularly well. In the sleep of 8 hours, 3-6 REM phases are found, which is about 20% of the total sleep time.
Sleep deprivation
If one is awakened from REM sleep several nights in a row (at least 4 nights), the percentage of REM in the undisturbed nights increases from 20% to 27% to 29%. This effect is referred to as the REM rebound effect.
