第一章
引言
節律性動作（例如行走等等）是和生物息息相關的動作活動。對經常使用上肢的靈長類而言，手部的節律性追蹤動作特別需要配合專注力的投入，是許多研究者探討的重要課題之一。然而在之前大部分的研究中，多數著重於行為表現。例如：動作的精準度；像是動作和目標的誤差值、以及時間差值等時序性上的影響。其中值得注意的是：依時序產生的節律性動作中，動作速度是一個影響動作表現與控制模式的重要參數。過去有文獻指出73,24，在追蹤動作頻率於一赫茲以上時，中樞控制機轉可能會從回饋控制轉變為前餽控制。同時，節律動作的速度改變對於探討中樞和周邊肌肉的功能性連結，是一個不可或缺的要素。
速度參數在過去的動作研究中，被證實會影響動作行為的表現，10,50,67,96以及關聯到脊髓中樞反射25,48與大腦中樞對於節律動作調控的改變。現代影像學呈現技術指出，速度參數的調控可能與基底核、小腦以及大腦的前運動和主運動區有相關。5,37,63,77,87但是影像學或腦電圖研究只能反應大腦中樞興奮區域與興奮區域間彼此連結的強度，對於腦皮質與動作肌肉間的相關與其代表的功能性意義，過去研究甚少著墨。
近年來隨著不同研究工具的發展，讓探討動作神經控制的方式有更多元的選擇。例如其中藉由量測力矩震顫8-12 Hz頻率的變化，來闡釋大腦中樞震盪的意義。19,71再者，有關腦部活動和肌肉收縮動作控制之間的功能性連結，近年來也藉由腦電、肌電訊號處理技術，發展出腦皮質-肌肉同調性(corticomuscular coherence)的定量估計。6,16,42,43,44,45,59,61腦皮質肌肉的同調性會和收縮力量大小、任務方式、中樞神經病變出現有不同的改變；6,16,42,43,44,45,59,61此外根據本研究室過去的發現，節律性動作造成皮質肌肉同調性的theta頻帶(4-8 Hz)有明顯的增加。27
本實驗利用皮質-肌肉同調性(corticomuscular coherence) 與力矩震顫頻譜結構差異來反應中樞震盪的改變，藉以觀察在不同追蹤速度快慢下，大腦中樞如何調控肌肉控制策略以維持節律動作的表現；並配合力量訊號和目標引導訊號之交互相關分析與變異係數，來定量動作契合度與動作表現的一致性和穩定性。希冀能夠更進一步找出動作程式(motor program)的生理證據，更加深刻體認大腦對不同追蹤速度的控制模式。
第二章
方法
本實驗同步量測在受試者分別進行三種速度不同的追蹤動作（0.5Hz,1.0Hz,2.0Hz）下，其腦電圖、肌電圖以及動作力量等生理電訊號。本實驗中有15名健康受試者，其中男性8位，女性7位；平均年齡為23.6±1.84 歲。本實驗量測硬體設備規格如下：（1）力量量測系統：多功能力矩量測器（Model: 9820P, AIKOH, JAPAN）、低通濾波器、 訊號放大器（Model: PS-30A-1, Entrain, UK）、數位示波器（Model: TDS2002, Tektronix, USA）等。（2）電生理訊號量測系統：重複性使用肌電圖電極（Silver/ Silver Chloride, 11mm, Model: F-E9-40-5, GRASS, USA）、肌電圖訊號交流放大器（Model: P511 series, GRASS-Telefactor, USA）等。（3）腦電圖量測系統：32頻道腦電圖放大器（NuAmp amplifier ;Neuroscan Inc. USA。收取系統與軟體如下：資料擷取卡（DAQ6221E, National Instrument, TX, USA）、以Labview 7.1（Laboratory Virtual Instrument Engineering Workbench, version7.1）來收取基本訊號、並以SCAN 4.3（Neuroscan, Inc. USA）來收取腦電圖訊號。最後以MatLab6.5（The Mathworks Inc. USA）進行訊號分析和處理，並以SPSS11.0（SPSS Inc. USA）來作為統計檢定用，顯著水準設定為p<0.05。
本實驗讓受試者進行3種頻率速度變化的右手食指追蹤動作，其強度為25%的最大自主收縮力量。實驗進行中受試者姿勢為坐姿下，雙手旋前並以副木固定動作的右手於桌面上，保持手部於放鬆彎曲姿勢下，伸出食指動作。肌電圖黏貼位置為右手第一背側骨間肌肌腹上。受試者右手食指之近端指間關節靠於多功能力矩測量器上以進行動作。腦電圖電極由帽套連接於標準10-20系統下之數個電極（Fp1, Fp2, Fz, F3, F4, FCz, FC3, FC4, Cz, C3, C4, CPz, CP3, CP4, Pz, P3, P4）位置。實驗動作狀況包含三種不同速度下的追蹤動作，分別為0.5Hz、1.0Hz、以及2.0Hz等的速度變化，在基本25％的最大自主收縮用力下，以12.5％的最大自主收縮當作節律性變化大小已進行每段30秒，重複10回的動作和生理訊號收集。不同受試者的動作順序均以拉丁方格來平衡量測順序。
本實驗於訊號處理方面，肌電圖會以6階Butterworth數位濾波器來去除掉60Hz的交流電干擾；腦電圖挑選最大相關於動作之C3，FC3電極作為分析，並以頻帶濾波0.1-50Hz濾波後來分析。腦電和肌電圖則以4階Butterworth數位濾波器來作各種不同速度下去除掉動作誤差的影響。並計算在C3腦電圖-肌電圖以及FC3腦電圖-肌電圖之同調性分析（coherence），求得同調性尖頻（perk coherent frequency）強度後以統計方法分析。而在對於動作表現的評量方面，利用變異係數分析（coefficient of variation）來估計動作力量的變異程度。並以比較實際產生力量與目標訊號之交互相關（cross correlation）以及目標訊號和產生力量訊號之時間延遲於在三種不同情況下，探討速度對於表現的影響。以及把動作力量以Welch方式之功率頻譜密度來作分析，以計算出功率頻譜下的尖頻頻率以及強度，來作為作力矩震顫之分析量測。本實驗以單因子重複量測變異數分析，以及LSD（least significant difference）法事後多重比較分析進行統計檢定。
第三章
結果
在C3/FC3腦電圖與第一掌骨指間肌肌電圖在theta頻帶同調性分析顯示，在較慢的追蹤動作（0.5，1.0赫茲）沒有明顯的同調性。以單因子重複變異數統計分析與事後多重比較分析顯示C3和FC3腦電極與肌電圖之同調性在theta頻帶強度與追蹤頻率有關（p<0.001），且C3腦電圖與肌電圖的同調性強度在1.0與2.0赫茲的追蹤動作中，其於theta頻帶的尖頻強度明顯地比0.5赫茲的尖頻強度大（p<0.05）；在FC3腦電極中，同樣發現到在theta頻帶的尖頻強度，隨著追蹤動作速度加快而增加（p<0.05）。腦電圖-肌電圖的同調性分析結果顯示，在不同的追蹤速度動作下，大腦皮質與神經肌肉活動的功能性聯繫，會隨著節律快慢而受到調節。
變異數統計分析的結果顯示，在三種追蹤速度的情況下，其施力變異性程度有明顯差異(p<0.001)。事後檢定分析發現，在較慢的0.5以及1.0Hz追蹤頻率下，其變異性值較2.0Hz追蹤頻率大。表示在較慢的0.5Hz以及1.0Hz的狀況下，中樞依賴回饋控制來作誤差調整因而增加變異性。在2.0Hz的情況下，則傾向前餽控制來產生動作模式，於是動作一致性較高。
施力與目標訊號之間的交互相關比較分析發現，在三種追蹤頻率下的相關係數以變異數統計分析顯示有明顯的差異(p<0.001)。事後比較分析顯示動作追蹤頻率越快的情況下，其相關係數越差，表示動作表現越差。同時變異數統計分析發現施力以及目標訊號時間延遲，在0.5 Hz以及1.0 Hz的情形下均為負值(0.5 Hz: -70.45±41.67 ms, 1.0 Hz :-21.30±139.60 ms)，表示產生施力落後目標訊號，而在2.0Hz的情形下為正值(34.36±152.60 ms)，表示產生施力超前目標訊號。
施力訊號功率密度頻譜分析發現，於8-12Hz頻帶有明顯的震顫尖頻。重複變異數統計分析結果顯示：尖頻強度和動作速度有相關 (p<0.001)。事後分析結果發現在2.0Hz尖頻強度最大(0.210±0.050 N2),，而0.5Hz的尖頻強度(0.154±0.040 N2)最小(p<0.01)。除此之外，在頻帶尖頻頻率分佈上發現到和追蹤頻率有明顯的相關(p=0.001)，越快的動作速度會產生越小尖頻頻率。(0.5 Hz: 9.32±0.63 Hz, 1.0 Hz: 8.86±0.03, 2.0Hz: 8.46±0.62 Hz) (p<0.01)。
第四章
討論
本研究中在腦電圖-肌電圖同調性分析結果顯示，在C3和FC3兩個與執行動作相關的腦電圖訊號以及手部第一掌骨指間肌肌電圖之功能性連結分析中，於執行較快之2.0赫茲下追蹤動作時，均於同調性頻譜之theta頻帶（4-8赫茲）位置出現顯著尖頻，此一結果和之前同調性研究之結果大多出現於beta頻帶（15-35赫茲）或是gamma頻帶（40赫茲以上）有明顯之不同。此外，皮質肌肉同調性分析象徵肌肉動作控制機制，反映出任務特別化（task specific）的性質；由於腦電圖-肌電圖同調性隨追蹤動作頻率不同而改變，顯示大腦皮質間和周邊肌肉的功能性連結會在不同動作速度而改變，代表中樞控制策略的改變，在神經生理上也證實速度確為動作程式上重要的參數。
本實驗中同時檢視動作行為表現包括：動作變異性與追蹤耦合程度等特徵，以瞭解不同追蹤頻率對動作控制的影響。結果發現施力曲線在較慢之0.5以及1.0赫茲下動作時，變異係數值有隨速度增加的趨勢；但是在最快之動作速度2.0赫茲下動作時，變異係數反為三者最低的狀況。可能原因為在較慢的動作中，也就是動作速度小於1.0赫茲的情形下，受試者不停使用視覺回饋修正追蹤活動的誤差，而誤差調整的過程會增加週期間手指追蹤動作的變異性；在大於1.0赫茲的動作情形下，目標動作過於快速變化，受試者無法有效率利用於回饋控制，便採取前餽控制而出現單純的動作模式，因誤差調整幾乎可以忽略，造成週期間追蹤動作相對變異性小。另一方面，以施力和目標訊號估計的追蹤耦合程度與時間差，耦合程度隨著動作速度加快而有下降的情形，可能原因為追蹤頻率增加時減少回饋校正機制的結果；而追蹤頻率增加也由施力落後目標動作的情形轉變成超前目標的狀況，可能原因為頻率增加傾向前餽控制效果，大腦預先以直覺產生節律動作，使得施力開始時間超前目標動作。
施力震顫功率頻譜分析結果發現，隨著動作速度的增加，頻譜8-12赫茲的中樞震盪尖頻強度有增加的趨勢。可能原因為中樞由於周邊執行較為快速動作時，造成中樞活動強度增加的狀況；同時快速追蹤動作發生尖頻位置有往低頻方向移動的現象，推測可能由於動作控制模式傾向前饋控制時，大腦不同部位間訊息交換較為單純，無需快速訊息交換並處理相關動作訊息，產生所造成之往低頻移動機制。
第五章
結論
本實驗主要的發現為：頻率快的正弦追蹤活動，在動作區與前動作區所產生皮質-肌肉同調性，較頻率慢的追蹤活動在theta頻帶有更明顯的同調性強度；頻率快的追蹤活動出現前饋控制的特徵；包括：低施力變異係數、施力訊號超前動作目標訊號且耦合程度較差：頻率慢的追蹤活動傾向回饋控制，與頻率快的追蹤活動之動作表現相反。因此，動作區與前額區所產生皮質-肌肉同調性theta頻帶可能與節律性活動的前饋控制有關。本實驗結果將可做為節律性動作控制理論之參考，提供訓練動作節律失調病患(例如巴金森氏症)的學理根據和參照。

Abstract

Introduction: Rhythmic tracking movement is critical to understanding neuromotor control of human. To enlighten the neurophysiological coupling during rhythmic tracking task, we conducted this study to analyze the cortico-muscular coherence, central oscillation changes, and outcome performance. Methods: Fifteen healthy subjects were recruited to complete rhythmic tracking movement of three different rates, by conducting load-varying isometric abduction contraction with visual feedback. The EMG of first dorsal interosseous, EEG（Fp1, Fp2, Fz, F3, F4, FCz, FC3, FC4, Cz, C3, C4, CPz, CP3, CP4, Pz, P3, P4）, and force output of index finger abduction were recorded. Results: Significant theta burst (4-8 Hz) in the EEGFC3-EMG and EEGC3-EMG coherences was typically found during fast rhythmic tracking task (2.0 Hz) rather than in the slower tracking conditions. (0.5 and 1.0 Hz). The peak amplitude of central oscillation in terms of 8-12 Hz in power spectra density of force fluctuation increased with tracking speed, but peak frequencies conversely decreased with task speed. The task consistency expressed by coefficient of variation in force generation profile was largest in the 1.0Hz condition, but was smallest in the 2.0 Hz condition. The correlation coefficient of force output and target signal decreased with tracking speed, and force output lead target signal as tracking speed increased. Conclusion: The present study compared corticomuscular coupling and task performance of visual tracking tasks at different speeds. Tracking speed substantially influenced control mode of finger rhythmic movement, in the context of speed-specific alternations in task performance and EEG-EMG coherence, the physiological drive from cortex to end-effector.

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