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Brain and Nerve No to Shinkei Volume 44, Issue 12 （December 1992）

Brain and Nerve 脳と神経 44巻12号（1992年12月発行）

Japanese English

原著

"高周波脳波ゆらぎ解析"による意識水準評価の試み Electrophysiological Evaluation of Human Consciousness Level by "Automated Fluctuation Analysis" of Human High Frequency EEG 中田宗朝 ¹ , 六川二郎 ¹ , 根路銘国政 ² , 外間政哲 ² Munetomo Nakata ¹ , Jiro Mukawa ¹ , Kunimasa Nerome ² , Seitetsu Hokama ² ¹琉球大学医学部脳神経外科 ²琉球大学医学部中央臨床検査部 ¹Department of Neurosurgery University of the Ryukyus, School of Medicine ²Department of University of the Ryukyus, School of Medicine キーワード： automated fluctuation analysis , high frequency EEG , fast Fourier transform , Lorentzian fluctuation , consciousness level Keyword: automated fluctuation analysis , high frequency EEG , fast Fourier transform , Lorentzian fluctuation , consciousness level pp.1087-1093

発行日 1992年12月1日 Published Date 1992/12/1

DOI https://doi.org/10.11477/mf.1406900417

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Abstract 文献概要
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　ジアゼパム静注による麻酔作用すなわち意識水準の微妙な変動や高次機能の変化は"高周波脳波ゆらぎ解析"によって的確に評価し得ることを前稿（脳神経44：117-124）で報告した。今回健常成人20名を対象として，被検者の自覚的な眠気の有無に焦点をおいて検討した。

　眠気を自覚していたS群（N＝8）では，眠気を否定したW群（N＝12）に比し，有意にSecond Lorentzが低下していた。また，Initial Lorentzに関しては，W群の全例で前頭部優位のパターンを認めたのに対してS群では全例で前頭部優位のパターンは消失していた。

　以上のことから，前稿に報告した薬物による効果であれ，今回検討した生理的な眠気であれ，意識水準は"高周波脳波ゆらぎ解析"によって的確に掌握し得ることが示された。

This study is done to clarify the clinical meaning of "Automated Fluctuation Analysis" of high fre-quency EEG in man especially focused on the fine alteration of consciousness level of the subjects.

Twenty normal volunteers were utilized for this study. They were divided into two groups, the subjects who felt sleepiness (Group S ; N = 8) and the subjects who denied it (Group W ; N =12) , during the EEG recording.

"Automated Fluctuation Analysis" of high fre-quency EEG had been presented in our previouspaper. In short, it is made of three steps, amplification of EEG signal, A/D conversion and Fast Fourier Transform by signal processor and extraction of Lorentzian parameters. Power spec-tral density (PSD) was displayed on log-log graph. Then the third step is performed by the best curve fitting program to the following equation, S (f) = S1/ [1+(f/fc1) 2] +S2/ [1+(f/fc2) 2], where S (f) is power spectral density at any frequency f, S1 and S2 are plateau level of initial and second Lorentz, respectively and fc, and fc2 are the corner or half power frequency of initial and second Lorentz, respectively. The algorithm of this program to extract these parameters were mathematically based on Brown & Dennis.

As results, 1. PSD of human high frequency EEG was composed of double Lorentzians and vanished into white level within 1kHz. 2. A topographical display of S1 value revealed hyperfrontal in group W, which is in accordance with the cerebral blood flow study by Ingvar. This pattern disappeared in group S. 3. There was statistical significances about S2 value between two groups, which strongly sug-gests the second Lorentz reflects the fine alteration of subcortical activation system. 4. "Automated Fluctuation Analysis" enabled us to manipulate EEG very simply and reliably.