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How can humans manipulate objects and perform skillful movements?
We routinely perform tasks with cutlery, kitchen utensils, hand tools, etc, which are mechanically unstable. This means that small perturbations arising from motor command variability or environmental disturbances may lead to unpredictable, inconsistent and unsuccessful movements. How can we perform such tasks despite of motor-output variability and important delays of the neural feedback?
We have recently shown that the central nervous system can control stiffness magnitude and geometry at the hand independently of the force to compensate for mechanical instability in the acquisition of a new motor skill Nature 414: 446-449 (2001), click to see more figures. This in turn implies that the CNS can coordinate the muscle activity so as to control the endpoint impedance of the arm. Voluntary control of limb impedance was predicted in 1984, but there had been no unambiguous evidence until our results. Besides potential clinical applications, this research may contribute to the design of efficient prostheses, robot controllers and haptic interfaces to feel and manipulate objects not directly accessible to hand held instruments e.g. in robotics surgery and in the nano/micro-world. This project is
a collaboration between (in alphabetical order) NUS:
National University of Singapore
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