Towards the Brain Dynamics under Chan Meditation Based on EEG Nonlinear Analysis
由初步的研究結果得知，資深的禪定者比起初修者較容易進入深定，禪定品質較好，伴隨有更顯著的身心變化。因此我們接著選取了23位資深的禪定者，與23位無禪定經驗者做進一步的研究。我們分別對於實驗組(禪坐)與控制組(閉眼放鬆)錄製40分鐘的腦電波，並選取在禪坐(放鬆)的前中後各5分鐘的錄製結果做複雜度指標以及頻譜分析。我們的實驗結果顯示，在禪坐的過程中前腦的alpha-1 (8-10Hz)以及後腦的beta成分的振幅較控制組增加，而閉眼放鬆的控制組則是theta增加。至於腦部動態參數複雜度指標則與beta有高度相關，也隨著禪坐過程而增加；至於控制組的複雜度指標則無顯著的變化。對照禪定者的口述推測：深定狀態時伴隨著內在光的出現，此時beta成分會增加，這種現象可以被 參數有效的反映出來。我們的結果證實，長期禪定訓練的確可以使禪定者在禪定時引發大腦皮質層的電訊號變化。
Orthodox Chan-Buddhist meditation brings multiform benefits to human beings but little has yet been disclosed regarding the electrophysiological characteristics of the CNS. This dissertation reports the effects of Chan meditation on CNS electrophysiological behaviors in the aspect of nonlinear brain dynamics. This work was mainly focused on the meditation electroencephalogram (EEG) signals, with the reference of a CAM instrument, ARDK. The ARDK measure might provide a feasible index for the effects of Chan meditation on the health. The results showed that Chan meditation could lead a better performance in the overall Health Condition Ratio especially in Body Energy and Musculoskeletal System. The observation allows us to infer that Chan meditation may cause a long-term effect on the practitioner to have a better health condition. Based on the nonlinear dynamical modeling, this study developed two analyzing schemes, the averaged complexity index and the similarity index (S), to investigate the effects and phenomena of meditation EEGs. In addition, the popular power spectral analysis and coherence evaluation were applied to meditation EEGs for comparison. EEG investigation started with the exploration of long-time records for both experimental (n=17) and control groups (n=16) to obtain the meditation EEG schema. Using an efficient algorithm of averaged complexity index, running complexity measures may reflect how the brain dynamics switches between various states of consciousness. The results showed that brain dynamics exhibited high indexes in deep meditation. Three different meditation scenarios have been identified from the running index chart. According to the preliminary findings of meditation scenarios, our study accordingly investigated the experienced Chan-meditation practitioners because, compared with novices, advanced practitioners might experience different physiological, cognitive, and psychological states and traits. Changes in the EEG characteristics in experienced Chan-Meditation practitioners (n = 23) during 40-minute of meditation were compared with those in the matched controls (n = 23) taking a rest for 40 minutes. complexity evaluation and spectral analysis were measured in three intervals, the first-, mid- and the last-5min sessions of Chan meditation or relaxing rest, each lasting for 5 minutes. Significant increase in frontal alpha-1 (8-10Hz) and occipital beta power was found during meditation as compared with the EEG under the rest, whereas an average increase of theta power was observed in the controls. In meditation, brain dynamics exhibited high indexes which correlated with more beta activity. Control subjects showed no significant change in complexity level. Deeper meditation state has been reported as implications of increased beta power which might probably correlate with a particular state of consciousness involving the inner-light perception. This can be more prominent by the approach of complexity estimation. Our results substantiate that long-term training with Chan-meditation does induce changes in the electro-cortical activity of the brain that are distinguishable from those observed for normal relaxation. This dissertation further presents our study on the brain interactions of experienced Chan-meditation practitioners (n = 12) varying with the meditation stages based on the nonlinear multivariate analysis. This method of similarity index (S) was used to measure the degree of possibly asymmetric coupling among multi-recording sites. Brain interactions were compared among three phases - 40-minute meditation (M), 5-minute Chakra-focusing practice (Z) and rest with closed eyes (R). Meditators exhibited, overall, stronger interactions among multiple cortical areas in meditation stages M and Z than in the R state. This enhancement was greater in the M stage when the meditator was accompanied by a thought-free and fully consciousness state. In the high-frequency band (>13Hz), the overall interdependence was also higher in both meditation stages than at baseline rest. However, the interaction strength, especially in the posterior regions, was greatest in the Z stage, which involved internal attention. Few electrode pairs were observed with significant pair-wise asymmetry in the Z state. The similarity is a possible characteristic of dense reciprocal and strong mutual interactions between multiple cortical areas during meditation - especially in the Z state in the high-frequency band. Results of this study demonstrate that profound Chan meditation induces various dynamic states in different phases of meditation, possibly reflected by nonlinear interdependence measure.
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