Table 1.7.1: Electrophysiological Characteristics of Sleep Stages
Stage of Sleep Predominant EEG Activity EOG Characteristics EMG Activity

1

Low voltage, mixed frequency
Slow
Decreased from awake
2
Sleep spindles and K complexes
None
Decreased from awake
3
Sleep spindles and slow waves
None
Decreased from awake
4
Mostly slow waves
None
Decreased from awake
REM
Low voltage, mixed frequency
Rapid
Nearly absent

Note. EEG = electroencephalographic; EOG = electrooculographic; EMG = electromyographic; REM = rapid eye movement. Derived from information in A Manual of Standardized Terminology, Techniques, and Scoring System for Sleep Stages of Human Subjects, by A. Rechtschaffen and A. Kales, 1968, National Institutes of Health Publication No. 204, Washington, DC: U.S. Government Printing Office.