title: Approximate entropy in the electroencephalogram during wake and sleep.
abstract: Entropy measurement can discriminate among complex systems, including deterministic, stochastic and composite systems. We evaluated the changes of approximate entropy (ApEn) in signals of the electroencephalogram (EEG) during sleep. EEG signals were recorded from eight healthy volunteers during nightly sleep. We estimated the values of ApEn in EEG signals in each sleep stage. The ApEn values for EEG signals (mean +/- SD) were 0.896 +/- 0.264 during eyes-closed waking state, 0.738 +/- 0.089 during Stage I, 0.615 +/- 0.107 during Stage II, 0.487 +/- 0.101 during Stage II, 0.397 +/- 0.078 during Stage IV and 0.789 +/- 0.182 during REM sleep. The ApEn values were found to differ with statistical significance among the six different stages of consciousness (ANOVA, p<0.001). ApEn of EEG was statistically significantly lower during Stage IV and higher during wake and REM sleep. We conclude that ApEn measurement can be useful to estimate sleep stages and the complexity in brain activity.
authors.affiliation: Division of Medical Oncology and Molecular Respirology, Faculty of Medicine, Tottori University, Yonago, Japan. burioka@grape.med.tottori-u.ac.jp
authors.forename: Naoto
authors.initials: N
authors.lastname: Burioka
authors.forename: Masanori
authors.initials: M
authors.lastname: Miyata
authors.forename: Germaine
authors.initials: G
authors.lastname: Cornélissen
authors.forename: Franz
authors.initials: F
authors.lastname: Halberg
authors.forename: Takao
authors.initials: T
authors.lastname: Takeshima
authors.forename: Daniel T
authors.initials: DT
authors.lastname: Kaplan
authors.forename: Hisashi
authors.initials: H
authors.lastname: Suyama
authors.forename: Masanori
authors.initials: M
authors.lastname: Endo
authors.forename: Yoshihiro
authors.initials: Y
authors.lastname: Maegaki
authors.forename: Takashi
authors.initials: T
authors.lastname: Nomura
authors.forename: Yutaka
authors.initials: Y
authors.lastname: Tomita
authors.forename: Kenji
authors.initials: K
authors.lastname: Nakashima
authors.forename: Eiji
authors.initials: E
authors.lastname: Shimizu
mesh_terms: D000328:Adult; D004569:Electroencephalography; D019277:Entropy; D006801:Humans; D008297:Male; D012890:Sleep / Q000502:physiology*; D014851:Wakefulness / Q000502:physiology*