探討禪坐腦電波空間分佈特性-使用小波和模糊分類法

Abstract

本篇論文主要目的是提出一套判斷腦電波中的α波的空間分佈特性的方法，並以此架構探討禪坐者與一般人的腦電波空間分佈的特性及差異性。 本方法首先將腦電波做小波(Wavelet)轉換，並利用小波的係數重建各頻帶的波形，再以各頻帶的能量比例判斷α波出現與否，並將這些萃取出來的α波能量向量(一段向量包含30個通道的分量)標準化；接著以模糊C-means(Fuzzy C-means)為基礎的分類法對標準化後的向量進行分類，並利用相關係數(Correlation coefficients)判斷分類數目。 在α波空間分佈的特性及差異性方面，初步發現(1)實驗組在禪坐中的α波減少程度不如控制組般顯著；(2)實驗組禪坐後前腦的α波會比控制組休息後多。從其他文獻中發現或許是因為禪坐中激發內側前額葉皮質(Medial Prefrontal Cortex)和前扣帶腦皮質(Anterior Cingulate Cortex)導致禪坐後之前腦α波增加。

The aim of this study is to propose a method for detecting α wave in EEG (electroencephalograph) and find the characteristics of EEG spatial distribution. We also investigated the difference of spatial characteristics between Zen-meditation practitioners (experimental group) and non-practitioners (control group). We firstly adopted wavelet transform to decompose EEG signals and reconstruct waves in each frequency band using wavelet coefficients. From the power ratio, we selected the candidates (normalized α-power vectors) for further spatial analysis. Fuzzy C-means based algorithm was applied to the normalized vectors to explore various brain spatial characteristics during meditation (or, at rest). Here we evaluated correlation coefficients to decide the number of clusters. From the results we found (1) the α power in the control group decreased dramatically but not in the experimental group, (2) after meditation, α power in the frontal area of meditators increased more than that of the control subjects (after resting-EEG recording). From the literatures, activating medial prefrontal cortex and anterior cingulated cortex during meditation may be the reason of increasing frontal α power.