Correlation dimension of the human sleep electroencephalogram

Abstract

Sleep electroencephalogram (EEG) was analyzed by nonlinear analysis. Polysomnography of a healthy male subject was analyzed and the correlation dimension was calculated. The mean correlation dimensions decreased from stage 'awake' to stages 1, 2 and 3, and increased during rapid eye movement (REM) sleep. These results were also seen at every sleep cycle. During each sleep cycle the correlation dimensions decreased for slow wave sleep, then increased for REM sleep.The mean correlation dimension of the sleep EEG in the second half of the night was significantly higher than those in the first half of the night. A significant change was seen both during REM sleep as well as in sleep stage 2. Nonlinear analysis may be a useful method in the analysis of the entire sleep electroencephalogram.

EEG responses to long-term audio–visual stimulation

“…Results by Kobayashi et al (2000) showed successful discrimination of sleep stages by measure of correlation dimension. AVS examined by Jin et al (2002) had decreasing effects on EEG complexity, shown by the first positive Lyapunov exponent as one of nonlinear measures of complexity.…”

Effect of Ethanol on Human Sleep EEG Using Correlation Dimension Analysis

“…The D2 values of the sleep EEG are influenced by certain parameters [29]. We also investigated the relationships between D2 and the inspective classification over the entire sleep EEG [19]. In those studies, the time lag, Ù, and the number of pairs, N, were changed, and then, the D2 were calculated.…”

“…D2 decreased from wakefulness to sleep stages 1+2 and 3+4, and increased during REM sleep for a different number of pairs. The D2 of every sleep stage had a tendency to converge to a value when the time lag, Ù, was 40 ms [19]. Since the polysomnogram was scored every 20 s, the time lag was fixed at Ù = 40 ms, based on previous findings and those of empirical studies [19,29].…”

“…The D2 of every sleep stage had a tendency to converge to a value when the time lag, Ù, was 40 ms [19]. Since the polysomnogram was scored every 20 s, the time lag was fixed at Ù = 40 ms, based on previous findings and those of empirical studies [19,29]. Only epochs free of artifacts were retained and included for analysis.…”

“…D2 decreases from wakefulness to stages 1, 2, and 3+4 non-REM, and increases during REM sleep [11,[17][18][19]. On the other hand, D2 values of stage 2 non-REM and REM sleep in patients with schizophrenia are significantly lower than in control subjects [17,20].…”