Sawtooth wave density analysis during REM sleep in normal volunteers.
OBJECTIVE
Sawtooth waves (STW) are a characteristic EEG feature of REM sleep but their source and function are unknown. We previously reported stereotypical properties of STW at stage REM onset, and alterations in bulbar postpolio syndrome. This study analyzes STW features throughout REM, in order to test the hypothesis that sawtooth wave activity may be predictable and have a consistent relationship across REM periods.


METHODS
Twenty polysomnographic recordings were scored for occurrence, duration, and frequency of STWs. STW density was calculated based on the number of bursts/min REM and duration of STW activity/min REM. The density measurements were statistically analyzed to assess for differences across REM periods.


RESULTS
STW density mean was 0.97 bursts/min REM (95% CI [0.85, 1.09]); 6.85 s/min REM (95% CI [5.95, 7.76]). STW frequency range was 1.5-5 Hz, mean 2.5 Hz. STWs occurred in bursts with a mean duration of 7 s (range 2-26 s). There was a lower density of bursts of STW activity per minute in the first REM period compared to the second, third, and fifth cycles.


CONCLUSIONS
This study reports STW density characteristics throughout REM sleep in normal subjects. Our density measurements suggest a difference in STW activity between the first REM period and later periods. Analysis of STW and related phenomena may increase the understanding of REM sleep mechanisms and may be useful to evaluate brainstem function during normal and pathological sleep.
Pearl
Phillip L
PL
Department of Neurology, Neurology/Neuroscience Program, Children's National Medical Center, George Washington University School of Medicine, 111 Michigan Avenue NW, Washington, DC 20010, USA. ppearl@cnmc.org
LaFleur
Bonnie J
BJ
Reigle
Suzanne C
SC
Rich
Anna Sophie
AS
Freeman
Amanda A H
AA
McCutchen
Charlotte
C
Sato
Susumu
S