Author(s): Hayashi K, Mukai N, Sawa T
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Abstract 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. Copyright © 2013 International Federation of Clinical Neurophysiology. Published by Elsevier Ireland Ltd. All rights reserved.
This article was published in Clin Neurophysiol
and referenced in Journal of Clinical & Experimental Pharmacology