ニオイ刺激によるヒトの脳磁図(MEG) : FFTによる周波数分析  [in Japanese] Magnetoencephalographic Responses to Odor and Non-odor by Fast Fourier Transformation Analysis in Humans  [in Japanese]

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Abstract

本研究では, ヒトにニオイ刺激 (アミルアセテート) と無臭刺激を与えたときの脳磁図を記録し, その信号を高速フーリエ変換 (FFT) によって解析し, ニオイ刺激によりどのような周波数が変動するか検討した. 対象は嗅覚正常者9名, 計測には37チャンネルの脳磁計を2基使用した. 刺激は右鼻腔に提示し, 脳磁図の記録を行った. 得られた波形をFFT処理し, 周波数帯域別および4~25Hzまで1Hz毎にスペクトル密度を算出した. このスペクトル密度がチャンネル毎, 周波数毎に各刺激条件で有意な変化があるかを検討した.<BR>その結果, 周波数帯域別ではいずれの帯域にも無臭刺激とニオイ刺激の比較では有意差は認めなかったが, 1Hz毎に検討すると以下のように有意差が認められた.<BR>(1) 無臭刺激とニオイ刺激の比較では7Hzに有意差を認めた. これは体性感覚やニオイ刺激特有の反応ではなく, アミルアセテートの刺激に対する認知機構との関係が示唆され, 嗅覚中枢の眼窩前頭野との関連が推測された.<BR>(2) 8Hzにおいて無刺激と無臭刺激, 無刺激とニオイ刺激の場合, 右側に有意差を認め, その有意差を認めた部位はほぼ同様なパターンを呈した. この変動は刺激による覚醒レベルの上昇によるものと考えられた.<BR>(3) 無刺激と無臭刺激の比較で11Hzのみ左側に, 無刺激とニオイ刺激の比較で11, 12Hzの左側に両者ともスペクトル密度の増大を認めた. この変動は注意力の集中によるものと推測された.<BR>(4) 無刺激とニオイ刺激の比較では14~24Hzまで多くの周波数で左側に有意差を認めた. このうち21, 22Hzの変動は無刺激と無臭刺激の比較でも認められた. この21, 22Hzの変動は無臭刺激, アミルアセテートによる三叉神経刺激によるものと考えられた. また, 無刺激とニオイ刺激の比較で認められた14-17Hz, 23-24Hzの変動はニオイ刺激によって生じた情動が関与していると考えられた.

Magnetoencephalographic (MEG) responses to odor (amyl-acetate) and non-odor stimuli for 1 second were recorded in 9 healthy volunteers (right handed) with a dual 37-channel SQUID (Magnes<SUP>TM</SUP>, Bti Co.) and evaluated by fast Fourier transformation analysis, with the following results:<BR>1. On MEG analysis, the spectral density increase in the left mid-central region at a frequency of 7 Hz was significantly greater in response to odor than in response to non-odor stimuli. This greater increase is apparently related to the presence of the odor perception mechanism in the orbital frontal area, a major center of the olfactory system.<BR>2. Both increased and decreased spectral density areas at a frequency of 8 Hz were observed over the right hemisphere when no stimuli was compared with non-odor and no stimulus compared with odor. These changes may reflect a high level of vigilance caused by stimulation.<BR>3. When no stimulus was compared with non-odor stimulation, a significant spectral density increase at a frequency of 11 Hz was noted. Similar trends were observed at frequencies of 11 and 12 Hz when no stimulus was compared with odor. These findings indicated increased attention in response to random presentation of odor and non-odor.<BR>4. Significant differences at frequencies from 14 to 24 Hz were noted in the contralateral hemisphere when no stimulus was compared with odor stimuli. MEG spectral densities at 21 and 22 Hz were also noted in the contralateral hemisphere when no stimulus was compared with non-odor stimulus.<BR>These differences apparently arise from the response of the somato-sensory cortex to non-odor stimuli and amyl-acetate.<BR>Alternation of MEG spectral densities at frequencies from 14 to 17 Hz and 23 to 24 Hz in the left hemisphere was noted when no stimulus was compared with non-odor and no stimulus was compared with odor. These results appear to be related to “emotions” of pleasantness and unpleasantness evoked by non-odor and odor.

Journal

  • Nippon Jibiinkoka Gakkai Kaiho

    Nippon Jibiinkoka Gakkai Kaiho 105(2), 142-151, 2002-02-20

    The Oto-Rhino-Laryngological Society of Japan, Inc.

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