Early to Bed or Sleep Revisited

TLDR: For many years, sleep was regarded as a passive process during which bodily functions slowed or stopped to allow reparative processes to operate, but the first inklings of a different theory were noted by sleep physiologists who described distinct changes in the electrical activity of the brain during sleep.

Abstract: For many years, sleep was regarded as a passive process during which bodily functions slowed or stopped to allow reparative processes to operate. The first inklings of a different theory were noted by sleep physiologists who described distinct changes in the electrical activity of the brain during sleep. 1 On the basis of electroencephalographic and eye movement recordings, sleep can be divided into alternating periods of rapid eye movement (REM) sleep that is associated with dreaming, and non-REM, or slow-wave sleep, which is divided into stages 1 through 4 according to specific EEG patterns and is not associated with dreaming. This alternating pattern of REM and non-REM sleep comprises a sleep cycle, several of which occur during each night's sleep. It was also discovered that an infant's sleep cycle is different from an older child's cycle and from an adult's sleep cycle. The length of each cycle, the amount of