探討禪定組與控制組的腦電波源定位之空間⾮ 線性相互依存關係

Abstract

腦功能的源定位是大腦研究領域的重要議題，建立大腦的電位模型是解決此問題的其一方法。 假設頭為一有多層殼並帶有不同導電度的半球模型，將小範圍內的神經元視為一產生電位的偶極子，以此建立電位模型模擬真實的腦電位訊號。在本論文中，我們採用一近似的模型來建立多層半球殼的腦電位模型，並開發一套尋找最適偶極子位置與強度的演算法。 為了比較實驗組（禪定）與控制組（閉眼休息）腦功能的空間特性差異，我們採用大腦電位模型來分析偶極子的特徵。結果顯示實驗組的第一第二偶極子皆集中在腦深部，左顳葉、右額葉區域，特別是在深部的額葉-中樞區域，此為禪定者將意識集中在禪心脈輪的結果。控制組的第一偶極子較易出現在左額葉、左頂葉及左枕葉，這些區域負責處理視覺處理、推理理解以及空間感官認知處理。第二偶極子則多集中在左顳葉、左頂葉及左枕葉。 為了分析腦的微狀態，我們採用自我組織映射圖將實驗組與控制組的一分鐘腦電波相似度矩陣分類。結果顯示實驗組比控制組有更多類似的微狀態重複，但不是每個類似的微狀態都有相似的偶極子空間特徵。實驗組的不活躍微狀態偶極子傾向出現在深度的左顳葉、左頂葉及左枕葉。而控制組活躍微狀態的偶極子則傾向出現在深到中度的頂葉及枕葉區域。 這一初步研究結果可為禪定與休息狀態下的腦動態差異帶來新見解。

Source focalization of specific brain functioning is an important task in the field of brain research. Constructing a dipole model to simulate real EEG is one of the methods for solving this problem. The dipole model considers the brain as a volume conductor with multiple concentric shells and assumes active neurons within a small region of the brain forming a current dipole. The first part of this study employed an approximate head model and developed an algorithm for dipole fitting. To compare the difference of spatial characteristics of brain functioning between Zen-meditation EEG and resting EEG, we apply the dipole model to analyze spatial statistics of dipole features. Our results show that both primary and secondary dipoles of Zen-meditation EEG concentrate in deep brain, with high probability of locating in left temporal and right frontal regions. Fronto-central regions of deep brain are also active regions, reflecting the effects of Zen-meditation practice at ChanXin-FaYan mailuns. With respect to resting EEG, primary dipoles appear more often in left frontal, left parietal and left occipital regions, which are responsible for visual processing and reasoning as well as integration of sensory information among various modalities and perception and cognition processing of spatial information. Secondary dipoles mostly locate in left temporal, left parietal, left occipital and right temporal regions. To analyze microstate phenomenon, we apply self-organizing map to cluster microstate similarity index matrixes (miSIMs) of one-minute Zen-meditation and resting EEG. We find that Zen-meditation EEG has more recurrent microstates than resting EEG. Not all recurrent microstates have similar dipole characteristics. Yet for Zen-meditation EEG, inactive microstates tend to have dipolar in the deep left temporal, left parietal and left occipital regions. For resting EEG, active microstates tend to have dipolar in the deep-to-mid parietal and occipital regions. This preliminary study may provide new insights into the differences of Zen-meditation brain dynamics.