rapid eye movement definition
Knowledge center. Rapid eye movement sleep, or REM, is one of the five stages of sleep that most people experience nightly. It is characterized by quick, random movements of the eyes and paralysis of the muscles. The amount of time spent in REM sleep varies significantly with age; it normally makes up around 20-25% of an adult humans total time spent asleep (on average about 90-120 minutes), and about more than half of an infant's. 1.