ABSTRACT
Human beings, like most other species on earth, have evolved in a world governed by a circadian cycle. This is reflected by the evolutionary development of an internal biological clock that normally synchronizes the daily cycle of sleep and wakefulness to the periodicity of the external environment.2 The normal sleep cycle appears to be composed of two distinct phases defined as REM-sleep and non-REM sleep. REM is an acronym for rapid eye movement. Most dream activity occurs during this phase of sleep, although dreaming is not limited to REM sleep.
