禪坐的心肺交互作用與大腦空間動態研究

Abstract

本論文主要說明我們研究禪坐對心肺功能和大腦空間動態的影響。為了比較禪坐的效果，我們找來兩個族群的自願受測者，分別為：禪坐修習者(實驗組)及沒學過禪坐的一般健康受測者(控制組)。 在心肺功能的研究中，我們探討心率變異性（heart rate variability, HRV）和心肺相位同步（cardiorespiratory phase synchronization, CRPS）特性。無論是在臨床和研究領域，心率變異性已被廣泛應用在了解自主神經系統的功能。心率變異性分析包括時域方法與頻域方法。在時域分析方面，我們用poincaré plot導出的參數來分辨禪定及一般放鬆後，接著執行持續專注測試(continuous attention task ,CAT）的效果。在頻域分析方面，自適應頻率範圍法(Adaptive-frequency-range, AFR，註記為：HRVAFR)可用來解決在禪坐族群中常會因低呼吸率造成高估HRV的問題。 CAT的研究結果顯示：實驗組受測者在經過禪坐練習後，顯著地改善了受測者在需要高度專注任務中的表現。同時交感神經/副交感神經活動平衡的干擾被高度降低。根據禪定修習者心率變異性的狀態可以看出他們在進行持續專注任務時有較佳的心理壓力管理能力。 心肺相位同步(CRPS)可以用來評估心臟與呼吸系統之間交互作用的效率。在我們由兩個族群搜集到的三組數據中，我們發現禪坐組的心肺相位同步特別高，這也許可作為長期禪定練習可以使心肺功能具有特殊的回復力的證明。尤其，一些資深的禪坐修習者即使在呼吸快速的情況下也能維持高度的心肺相位同步程度。 大腦中的空間動態研究中，我們從區域神經網絡的非線性空間相互關聯(nonlinear interdependence)特性的角度，來研究禪坐對大腦電生理反應的影響。其中我們特別著重α波為主的腦電圖。我們採用連續時間的小波變換法來尋找具有大量α波活躍的段落。我們所探討的非線性空間相互關聯由相似性指標(similarity index ) S(X|Y)來量化，來源信號Y對接收信號X的影響，被應用在以多通道腦電波訊號重建非線性動態模型。 我們將不同腦皮質區域間的非線性空間相互關聯特性，分成五個神經網絡區來探討，包含額葉，枕葉，右顳葉，左顳葉和頂葉(中間)地區。實驗組的測試流程是專為實驗組設計的，包含休息階段（R, 禪定前基準值記錄）、禪坐階段（M）和單一輪點專注階段（C）。 研究的結果，實驗組在禪坐階段(M)和專注輪點階段(C)階段比休息(R)階段在不同腦皮質區域間呈現出較強的交互關係。而禪定組與控制組間的比較則可以發現，禪定組的大腦皮質區相較於控制組有較佳的交互作用。

This dissertation presents the results of our research work on the effects of Chan meditation on cardiorespiratory performance and brain spatial dynamics. For comparison, two groups of voluntary subjects were investigated, Chan-meditation practitioners (experimental group) and normal, healthy subjects without meditation experience (control group). In the study of cardiorespiratory functions, we investigate heart rate variability (HRV) and cardiorespiratory phase synchronization (CRPS) characteristics. HRV has being extensively employed in understanding the function of autonomic nervous system both in clinics and researches. HRV analysis involves time- and frequency-domain methods. In time-domain analysis, parameters derived from Poincaré plot were adopted to discriminate between Chan-meditation effect and normal-relaxation effect on continuous-attention-task (CAT) performance. In frequency-domain HRV analysis, adaptive-frequency-range (AFR) scheme, HRVAFR, was developed to resolve the issue of overestimating HRV under the condition of slow respiration rates that often occur in the group of Chan-meditation practitioners. In CAT study, the results demonstrated that experimental subjects, after Chan-meditation practice, exhibited significant improvement in conducting task requiring superior attention, whereas disturbance in the balance of sympathetic-parasympathetic activity was highly reduced. HRV behaviors of the Chan-meditation practitioners demonstrated their better performance in managing the mental stress when conducting continuous attention tasks. The effectual co-action between the cardiac and respiratory systems was evaluated by the degree of cardiorespiratory phase synchronization (CRPS). In our comparison of the three data sets collected from the two groups, our findings of significantly higher CRPS in Chan-meditation group might provide the evidence of the extraordinary rejuvenation process of cardiorespiratory functions through long-term Chan-meditation practice. To avoid confusion, use the same name for meditation. Particularly, advanced practitioners exhibit a constantly high degree of cardiorespiratory phase synchronization even during rapid breathing. In the study of brain spatial dynamics, we investigated the effects of Chan meditation on brain electrophysiological behaviors from the viewpoint of spatially nonlinear interdependence among regional neural networks. Particular emphasis was laid on the alpha-dominated EEG (electroencephalograph). Continuous-time wavelet transform was adopted to detect the epochs containing substantial alpha activities. Nonlinear interdependence quantified by similarity index S(X|Y), the influence of source signal Y on sink signal X, was applied to the nonlinear dynamical model in phase space reconstructed from multi-channel EEG. Nonlinear interdependence among various cortical regions was explored for five local neural-network regions, frontal, posterior, right-temporal, left-temporal and central regions. Experimental protocol designed particularly for the experimental group involved three different stages, at rest (stage R, pre-meditation background recording), in Chan meditation (stage M) and the unique Chakra-focusing practice (stage C).