Slow-wave sleep (SWS), often referred to as deep sleep, consists of stages three and four of non-rapid eye movement sleep, according to the Rechtschaffen & Kales (R & K) standard of 1968. There is not a clear distinction between stages three and four. Stage three has 20-50 percent delta activity, whereas stage four has more than 50 percent. As of ...
NREM sleep.
Slow-wave sleep: Stage 3 and 4 non-rapid eye movement (non-REM) sleep. Slow-wave sleep is characterized by brain wave patterns (electroencephalogram or EEG) with a frequency of less than 4 Hz and peak-to-peak amplitude of 75 microV.
See sleep stages.