What is REM sleep

REM has been shown to have links to memory consolidation and to learning. People who are deprived of REM sleep through sleep deprivation might have problems remembering. They also might have trouble learning new things.
During REM sleep, the large voluntary muscles of the body are paralyzed. Conversely, brain activity is quite intense at this stage. REM sleep is the stage of sleep when people dream. It is thought by sleep researchers that the paralysis of the large muscles occurs to keep people from acting out their dreams. REM sleep is sometimes called paradoxical sleep, due to the contrast between the high brain activity and the physical immobility of the sleeper.

When in REM sleep, breathing and heart rate are faster than normal. The sleeper's legs, face, and fingers twitch. And of course, there is rapid movement of the eyes. This is the stage of sleep when people have intense dreams, although they might not remember the dreams upon waking.

The stages of sleep proceed in cycles throughout the night. The cycles might repeat as many as five times per night. The length and intensity of REM sleep increases with each succeeding cycle. During the first cycle, REM sleep might be only 10 minutes long, while during the last cycle it might stretch to 90 minutes.

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