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In this study, finger force control abilities are quantified by the concept of multi-finger synergy in conjunction with uncontrolled manifold (UCM) analysis. Two indices, namely, repeatability and flexibility, representing features of multi-finger synergy were proposed to overcome the limitation of previously introduced indices, such as floor effects and distortion problems. The proposed indices were applied to stroke patients and healthy adults through specifically designed experiments. The experimental results showed a clear difference between stroke patients and healthy adults. Also, interestingly, there was a difference in an outcome between two-stroke patient subgroups: stroke patients in whom the dominant hand was affected and non-dominant hand was affected groups.
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http://dx.doi.org/10.1109/TNSRE.2019.2915816 | DOI Listing |
Neuroscience
August 2025
Department of Kinesiology, The Pennsylvania State University, University Park, PA 16802, USA. Electronic address:
We addressed the controversy on the relative role of the reciprocal and coactivation commands in the neural control of force in multi-finger tasks. Specifically, we tested the hypothesis that a mechanical variable serving as a proxy of the coactivation command will scale with force magnitude. We also explored indices of force-stabilizing synergies assessed at the level of the reciprocal and coactivation commands to the hand and to the individual fingers and at the level of finger coordination.
View Article and Find Full Text PDFHum Mov Sci
June 2025
Department of Kinesiology, The Pennsylvania State University, University Park, PA 16802, USA.
We explored the hypothesis on two sources of finger force variance in multi-finger accurate force production tasks, related to variability in the sharing of total force among finger forces and to sensory-based covariation of the finger forces. This hypothesis was explored within the space that did not affect task-specific performance variable (the uncontrolled manifold, UCM) and within the space that affected this variable (orthogonal to the UCM, ORT). Young, healthy subjects performed steady-state accurate total force production tasks with and without targets for the individual finger forces.
View Article and Find Full Text PDFHum Mov Sci
October 2024
Department of Health and Kinesiology, Purdue University, West Lafayette, IN, USA. Electronic address:
Humans frequently prepare for agile movements by decreasing stability. This facilitates transitions between movements but increases vulnerability to external disruptions. Therefore, humans might weigh the risk of disruption against the gain in agility and scale their stability to the likelihood of having to perform an agility-demanding action.
View Article and Find Full Text PDFNeuroscience
July 2024
Department of Kinesiology, The Pennsylvania State University, University Park, PA 16802, USA. Electronic address:
We tested a hypothesis on force-stabilizing synergies during four-finger accurate force production at three levels: (1) The level of the reciprocal and coactivation commands, estimated as the referent coordinate and apparent stiffness of all four fingers combined; (2) The level of individual finger forces; and (3) The level of firing of individual motor units (MU). Young, healthy participants performed accurate four-finger force production at a comfortable, non-fatiguing level under visual feedback on the total force magnitude. Mechanical reflections of the reciprocal and coactivation commands were estimated using small, smooth finger perturbations applied by the "inverse piano" device.
View Article and Find Full Text PDFJ Neural Eng
December 2023
Department of Bioengineering, Imperial College London, London, United Kingdom.
The absence of intuitive control in present myoelectric interfaces makes it a challenge for users to communicate with assistive devices efficiently in real-world conditions. This study aims to tackle this difficulty by incorporating neurophysiological entities, namely muscle and force synergies, onto multi-finger force estimation to allow intuitive myoelectric control..
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