Paradoxical sleep (synonymous with REM Sleep) is a period of sleep that includes rapid eye movements, loss of muscle tone, and sometimes trembling in the legs. This sleep period in which dreams occur is the central part of the sleep process. Paradoxical sleep in adult humans occurs in cycles and accounts for 20-25% of a regular night’s sleep. The rate of paradoxical sleep increases with sleep after sleep deprivation. Hypnotics and stimulants also change this ratio.