經皮神經電刺激應用於主要動作皮質對於動作學習時皮質興奮性與前額葉活化之影響：經顱磁刺激與近紅外線吸收光譜研究

Abstract

中文摘要 前言：根據先前的實驗結果所發現，經皮神經電刺激對於主要動作皮質的活性所造成的影響，無法與動作學習所產生的興奮性神經塑性有所區別，因此本實驗主要是為了瞭解頭顱經皮神經電刺激以及動作學習所產生去抑制現象之間的交互關係，而本實驗主要藉由量測在執行內隱式順序性動作學習的受試者主要動作皮質興奮性的改變，而本實驗另外使用近紅外線吸收光譜來量測前額葉在動作學習的過程中血液動力學反應的改變。方法：本實驗總共從社區以及大學徵招了48位年輕受試者，而受試者將會被隨機分配到電刺激組與電刺激伴隨動作學習測試組，而受試者需要完成兩次實驗，包含經皮神激電刺激和假刺激，而兩次測試則是隨機分配，試驗的間隔則需要大於一周，而本實驗成果測試項目包括：動作誘發電位、皮質內誘發、皮質內抑制、前額葉血液動力學變化以及順序性反應性動作測試中的反應時間長度，綜合以上神經生理或是行為科學上的量測來觀察經皮神經電刺激的效果。結果：在動作電位上則是發現有接受經皮神經電刺激的兩種試驗顯著上升，包含單純接受電刺激介入以及電刺激介入伴隨動作表現量測之情形，發現動作學習對於經皮神經電刺激所產生的效果產生協同作用，而在有動作執行的兩組(動作執行伴隨電刺激或假刺激)則是發現皮質內抑制所產生的抑制量明顯上升，而有電刺激伴隨動作執行量測的組別改變抑制的百分比顯著較假刺激明顯，而皮質內誘發則是在有電刺激的兩組(有無動作執行)顯著下降，但是組間的比較則是沒有明顯差異，而順序性反應時間測試中則是兩組(電刺激/假刺激)隨著練習的次數增加時明顯的降低反應時間，但是電刺激介入並沒有顯著影響動作表現，因此兩組間則是沒有顯著差異，而在前額葉血液動力學變化中則是只有在電刺激介入的情形有顯著效應，而在初始練習時發現有活性明顯上升的情形，而在30分鐘後測時發現顯著低於初始值的活性，因此代表電刺激的組別有一定的幫助學習固化的現象。討論：經皮神經電刺激顯著對皮質脊髓神經元產生明顯的興奮性誘發，但是同時間則發現皮質內抑制也有明顯增加的情形，而皮質內抑制上升則是被認為會干擾皮質重組或是去覆蓋現象(unmasking)，而顯著動作的電位上升伴隨皮質內誘發明顯的下降則是有可能在皮質內誘發的量測中發生天花板效應，而在動作表現上則沒有發現明顯電刺激造成的效應，結論：本實驗證實經皮神經電刺激明顯增加主要動作皮質內之興奮性，而且動作練習對於經皮神經電刺激所產生的效果產生聯合反應，需要更進一步大於24小時的長期追蹤，或是增加電刺激介入的劑量，來進一步討論經皮神經電刺激的效應。

AIM: The relationship between cranial transcutaneous electrical nerve stimulation (TENS) stimulation and cortical excitability change during motor learning process is unknown. This study aims to explore the effects of cranial TENS application on cortical excitability of primary motor cortex (M1) during implicit sequential motor learning process in normal subjects. Prefrontal activation pattern in learning process was also monitored by Near-infrared spectroscopy (NIRS). METHODS: 48 volunteers were recruited from colleges and communities. Subjects were randomized into TENS stimulation group (Stimulus-TENS/Sham) and TENS stimulation with motor task group (Motor-TENS/Sham). Subjects in both groups need to accomplish two trials (TENS or sham stimulation), the interval between trials was more than 1 week. Motor evoked potential (MEP), intracortical inhibition (ICI) and intracortical facilitation (ICF), Serial reaction time task and NIRS were measured to monitor physiological and behavioral change process in motor learning. RESULTS: MEPs amplitude in both Motor-TENS and Stimulus-TENS group increased significantly. MEP amplitude of Motor-TENS were significantly higher than Stimulus-TENS in followed up 60 mins. Motor task induced synergistic effect on enhancement of MEP amplitude. Higher suppression effects of ICI were also found in both Motor-TENS and Motor-Sham. Motor-TENS go higher suppression of ICI than Motor-Sham which revealed synergistic effect of TENS stimulation. The ICF was also decreased in Motor-TENS and Stimulus TENS. However, between group comparison showed no significant different. In SRTT performance, reaction times significantly improved both in Motor-TENS/Sham but no difference between TENS and sham stimulation. Prefrontal activation showed significant time effect in TENS-Motor only. Increment activation in initial learning and following decrease activation in retention test was observed. Consolidation effect in Motor-TENS than Motor-Sham was also noted. DISSCUSSION: TENS intervention increased corticospinal neuron excitability. However, significant increase suppression induced by ICI may indicate disruption of cortical representation. Increment of ICF concurrent with increment MEP showed ceiling effect existed in ICF measurement. TENS intervention showed weak effect to altered motor learning process. CONCLUSION: TENS stimulation increase cortical excitability and inhibitory shift of intracortical circuits. Motor practice played a facilitation role to altered cortical excitability which induced synergistic effect on TENS intervention. Further study should be done to investigate the effect of TENS with long-term (more than 24 hour) effect or increase times of stimulus program.