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Updated: May 9, 2026
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Published on: November 30, 2017
Simultaneous bicoherence analysis of occipital and frontal electroencephalograms in awake and anesthetized subjects
Kazuko Hayashi1, Nobuhiro Mukai2, Teiji Sawa3
1Department of Anesthesiology, Nantan General Hospital, Japan; Department of Anesthesiology, Kyoto Prefectural University of Medicine, Graduate School of Medical Science, Kyoto, Japan.
Objective:
Occipital electroencephalogram (EEG) activity is known to be different from the frontal EEG during wakefulness and anesthesia. However, less is known about occipital non-linear dynamics analyzed by EEG-bicoherence, which can reflect the oscillatory features that are dependent on thalamocortical modulation.
Methods:
Forty patients were anesthetized using sevoflurane (1% or 3%) combined with remifentanil. Frontal and occipital EEGs were simultaneously collected, and bicoherence was analyzed before and after induction of anesthesia.
Results:
Occipital awake EEGs often demonstrate a bicoherence α peak, differing from frontal awake EEGs in the absence of bicoherence growth. With 1% sevoflurane, occipital α bicoherence disappeared and frontal α bicoherence peaks appeared. Although 3% sevoflurane caused an increase in occipital δ-θ normalized power, similar to the frontal region (peak relative δ-θ power, 13.1 ± 2.2% vs. 12.2 ± 2.7%, p>0.05), occipital bicoherence showed no growth in any frequency area, contrasting with the frontal bicoherence spectrum with a conspicuous peak in the δ-θ area (19.8 ± 8.9 vs. 43.6 ± 13.8, p<0.05).
Conclusions:
The occipital bicoherence spectrum in the peri-anesthesia period is quite different from the frontal bicoherence spectrum, which is not usually obvious in the power spectrum.
Significance:
Nonlinear regulation of the occipital EEG is different from the frontal EEG during every stage of anesthesia.
