ABSTRACT
Sleep onset is characterized by slow rolling eye movements of several seconds' or more duration and a mixture of frequencies of relatively low voltage but typically dominated by theta waves. Delta or slow wave sleep is characterized by high voltage, slow waves. The increasing presence of large delta waves indicates the onset of delta sleep. Waking the sleeper is most difficult at this time; hence, delta sleep is considered the deepest stage of sleep. The physiology of the body during rapid eye movement (REM) is quite different from that during non- REM (NREM). The stages of sleep in the average young adult show a fairly regular cyclic alteration. Environmental influences such as daylight, traffic noises, and the activity of other people tend to make prolonged sleep more difficult. The relationship between length of prior wakefulness and the amount of delta that follows is direct.
