探討打瞌睡腦波之神經調控機制

Abstract

人腦中存在有許多的功能區域性腦波律動(Brain rhythm)，與人類的行為有關聯性的連結，很多過去的文獻指出，大腦許多皮層的腦波律動都與打瞌睡的程度有正相關性。因此，我們假設有腦波律動調控機制，透過大腦皮層間的神經傳導或者散佈在大腦各處不同的腦波律動調控子來調控大腦皮層的神經律動。 在此研究中，我們利用虛擬環繞場景結合六軸動態平台，研究從清醒到昏睡時的腦電波活動，並探討打瞌睡腦波的神經調控機制。了解不同大腦皮層之間的互動。我們使用時頻分析與獨立成份分析(Independent Component Analysis, ICA)去找出腦波律動調控子(modulator)，並且發現有兩種不同種類的腦波律動調控子，分別調控大腦律波的alpha頻帶與theta-beta頻帶。 本實驗結果顯示，當受測者開始打瞌睡的時候，alpha (8-12 Hz)頻帶調控子(alpha-band modulator)強度會持續性的增強，而進入深度瞌睡時， alpha頻帶調控子強度則會輕微的降低。另外，受測者清醒狀態從輕度至深度瞌睡過程中，theta (4-7 Hz)頻帶調控子(theta-band modulator)強度則持續的增強。跟瞌睡程度有正向相關性，透過實驗結果證明本研究提出的分析方法，讓我們對神經調控系統有更清楚的了解。

Rhythmic electrical fluctuations measurable on the human scalp were the first direct evidence for the link between electrophysiological processes in the brain and behavior. Several studies have shown the EEG power spectra at various scalp locations are correlated with drowsiness in various sustained-attention experiments. We hypothesize that there seems to be modulators mediated spectral activations of the cortical areas by intra-cortical feedback loops, or distributed over different parts of the brain comprising a large number of neurons. In this study, we investigate the neuromodulatory system from alertness to drowsiness in a realistic virtual-reality based driving environment to understand the interactions among different cortical areas. We model spectral fluctuations of independent components from EEG activations as the actions of independently modulator processes, and report two main classes of spectral modulation patterns, alpha modulator and theta-beta modulator. The theta-beta modulator fluctuates very little during the low LDE periods, and increases monotonically from low LDE to high LDE. Different with the theta-beta band, the alpha modulator fluctuates very large during the low LDE periods. Therefore, the theta-beta modulator is high correlated with performance changes, and alpha modulator in this study might be partially contributed by cortical idling. The neuromodulatory system can be explored more by the method we propose here.