다중 손가락 모멘트 제어에서 손가락 힘과 모멘트의 계층적 시너지 작용 (Hierarchical Synergy Adjustment and Finger Specialization in Multi-digit Moment Production)

서지정보

· 발행기관 : 한국운동역학회
· 수록지 정보 : 한국운동역학회지 / 34권 / 3호 / 115 ~ 124페이지
· 저자명 : 송준경, 김기태

초록

Objective: Based on the uncontrolled manifold (UCM) framework, this study investigated the hierarchical organization of redundant motor elements in multi-digit prehension, focusing on moment production across two control hierarchies.
Method: Twelve adult males participated in the current experiment where they grasped a customized handle to generate and maintain target moments under isometric conditions in both pronation and supination directions. The forces exerted by the digits, recorded via transducers on the handle, underwent UCM analysis. This analysis quantified the synergistic actions across the upper and lower control hierarchies for stabilizing moments and grip forces. Additionally, synergy properties for lateral and medial fingers were analyzed to assess their distinct contributions (finger specialization) to moment and force stabilization.
Results: Our findings revealed that the thumb and virtual finger contribute differently to net moment generation according to the direction of the moment, reflecting the different abilities of the individual fingers to produce moments. In the upper hierarchy, synergistic actions were notably stronger, effectively stabilizing both moments and grip forces. In contrast, the lower control hierarchy demonstrated a lack of synergy in force stabilization (trade-off synergy), although synergy in moment stabilization was preserved. Further, lateral fingers were found to play a more significant role in stabilizing moments compared to medial fingers.
Conclusion: The pronounced synergy in grip force observed in the upper hierarchy implies that grip stabilization is likely an intrinsic strategy of the central nervous system, rather than merely a mechanical consequence. Furthermore, synergistic covariations of digit moments in both hierarchies indicate the neural controller's capability to generate synergies across hierarchies for stable multi-digit moment production. The notable contribution of lateral fingers in moment stabilization provides supporting evidence of finger specialization. Overall, this study elucidates the hierarchical interplay of redundant elements to achieve task-specific stability, especially in multi-digit prehension.

영어초록

Objective: Based on the uncontrolled manifold (UCM) framework, this study investigated the hierarchical organization of redundant motor elements in multi-digit prehension, focusing on moment production across two control hierarchies.
Method: Twelve adult males participated in the current experiment where they grasped a customized handle to generate and maintain target moments under isometric conditions in both pronation and supination directions. The forces exerted by the digits, recorded via transducers on the handle, underwent UCM analysis. This analysis quantified the synergistic actions across the upper and lower control hierarchies for stabilizing moments and grip forces. Additionally, synergy properties for lateral and medial fingers were analyzed to assess their distinct contributions (finger specialization) to moment and force stabilization.
Results: Our findings revealed that the thumb and virtual finger contribute differently to net moment generation according to the direction of the moment, reflecting the different abilities of the individual fingers to produce moments. In the upper hierarchy, synergistic actions were notably stronger, effectively stabilizing both moments and grip forces. In contrast, the lower control hierarchy demonstrated a lack of synergy in force stabilization (trade-off synergy), although synergy in moment stabilization was preserved. Further, lateral fingers were found to play a more significant role in stabilizing moments compared to medial fingers.
Conclusion: The pronounced synergy in grip force observed in the upper hierarchy implies that grip stabilization is likely an intrinsic strategy of the central nervous system, rather than merely a mechanical consequence. Furthermore, synergistic covariations of digit moments in both hierarchies indicate the neural controller's capability to generate synergies across hierarchies for stable multi-digit moment production. The notable contribution of lateral fingers in moment stabilization provides supporting evidence of finger specialization. Overall, this study elucidates the hierarchical interplay of redundant elements to achieve task-specific stability, especially in multi-digit prehension.

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