單指與雙指在自主施力表現之行為與動作電位分析

The analyses of behavioral and movement-related cortical potentials associated with single or two finger(s) voluntary force production

關於手指活動的神經機制，先前的研究已經證實，位於動作皮質的神經元具有控制手指動作的高層策略，就運用單指施力產生牽制效應的研究發現，慣用手食指在力量誤差、手指協調及神經策略上，均顯著異於其他手指。目的：本研究針對右手食指就單手及雙手配合同指及異指，設計五組不同手指施力動作，在相同時間內執行固定最大肌力50%力量速率的情況下，藉由手指施力的準確度、牽制力量等二項結果，進一步地就手指協調層面探討，並輔以分析大腦高層運動中樞在不同施力動作間的神經策略機制。方法：15 位受試者皆進行五組不同之動作任務，前二任務為單手單指 （右手食指組、右手中指組），後三任務依序為單手異指組 （右手食指+右手中指）、雙手同指組 （右手食指+左手食指）、雙手異指組 （右手食指+左手中指）。施力行為分析的依變項為施力任務準確度及非作用指之牽制力，並將五種任務的動作相關電位訊號，依照動作準備期、動作開始期、施力上升期、施力穩定期等四段腦波成份進行比對與分析。結果：發現所有手指任務之中，在施力上升期於左側大腦皮層 （C3），以右手食指組之施力準確度最高、牽制效應最低，該組之動作電位亦高於其他任務；在動作電位成份方面，施力過程中以施力上升期之動作電位高於其他電位成份。整體而言，獨立性較高的食指一旦進行雙指施力任務，動作電位即明顯降低；而在三組雙指任務的腦波動作電位結果中，雙手異指組明顯高於雙手同指組及單手雙指組。結論：說明雙手施力動作間，在單指與雙指間存有特定之神經動作主導控制策略。

The neural mechanisms related to finger coordination have been proved that the neurons of motor cortex dominate the higher level of motor strategies associated with finger control. Purpose: This study applied the enslaving effect found among single finger and slaved fingers, and designed five different tasks to perform constant 50% rate of force finger force development. The behavior of fingers in terms of accuracy of force traces, the sum of forces produced by slaved fingers, as well as the movement-related cortical potentials have been analyzed to explore the cortical motor mechanism associated with strategies within single or two finger force control. Methods: 15 college subjects performed five different tasks. The first two tasks were one finger within one hand (e. g. the index finger of right-hand, the middle finger of right-hand). The other three tasks were two fingers within one hand (index and middle fingers of right-hand), the identical finger of two hands (the index fingers of both hands), and the different fingers of two hands (the right index of right hand and the middle finger of left hand). The force traces generated by the assigned finger, the force generated by the slaved fingers, and the movement-related cortical potentials of the five tasks were analyzed. The components of movement-related cortical potentials were divided into four different phases which were the preparatory phase, the motor phase, the ramp phase and the static phase. Results: The results showed that the right index finger revealed the highest accuracy of force trace with the lowest enslaving and the highest amplitude of movement-related cortical potentials. Within the four components of cortical potentials, the ramp phase demonstrated the highest amplitude comparing to the other three components. However, the amplitude of the right index finger decreased while performing tasks with other fingers in either hand. For those two finger tasks, the amplitude of different finger of two hands demonstrated higher level than either identical finger of two hands or two fingers within one hand. Conclusion: The study implied that there existed specific dominance at the higher level of motor system while performing finger tasks with either one or two fingers in both hands.