ABSTRACT
Many sleep researchers use a couple of central recording sites, one on the top-right side of the head and one on the top-left side of the head. For many years, the entire squiggly electroencephalograph (EEG), electroocculograph (EOG), and electromyograph (EMG) lines that make up a sleep recording seemed to be just a chaotic mess. When a polysomnographer sees a combination of alpha and theta activity, with the majority of the activity in the theta range. Sleep is separated into two distinct states, non-rapid eye movement sleeps (NREM) and rapid eye movement sleep (REM). As time progresses, deeper stages of sleep are signaled by the appearance of slow, high amplitude delta waves, which have a frequency of between 0.5 and two cycles per second. The progression of sleep stages is modified by age, time awake, time of day, environmental characteristics, sleep disorders, and a variety of other factors.
