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Impedance control and internal model use during the initial stage of adaptation to novel dynamics in humans.

Milner, TE and Franklin, DW (2005) Impedance control and internal model use during the initial stage of adaptation to novel dynamics in humans. J Physiol, 567. pp. 651-664. ISSN 0022-3751

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Abstract

This study investigated the neuromuscular mechanisms underlying the initial stage of adaptation to novel dynamics. A destabilizing velocity-dependent force field (VF) was introduced for sets of three consecutive trials. Between sets a random number of 4-8 null field trials were interposed, where the VF was inactivated. This prevented subjects from learning the novel dynamics, making it possible to repeatedly recreate the initial adaptive response. We were able to investigate detailed changes in neural control between the first, second and third VF trials. We identified two feedforward control mechanisms, which were initiated on the second VF trial and resulted in a 50% reduction in the hand path error. Responses to disturbances encountered on the first VF trial were feedback in nature, i.e. reflexes and voluntary correction of errors. However, on the second VF trial, muscle activation patterns were modified in anticipation of the effects of the force field. Feedforward cocontraction of all muscles was used to increase the viscoelastic impedance of the arm. While stiffening the arm, subjects also exerted a lateral force to counteract the perturbing effect of the force field. These anticipatory actions indicate that the central nervous system responds rapidly to counteract hitherto unfamiliar disturbances by a combination of increased viscoelastic impedance and formation of a crude internal dynamics model.

Item Type: Article
Uncontrolled Keywords: Adaptation, Physiological Arm Computer Simulation Elasticity Feedback Female Humans Male Models, Biological Motor Skills Movement Muscle Contraction Muscle, Skeletal Postural Balance Task Performance and Analysis Viscosity
Subjects: UNSPECIFIED
Divisions: Div F > Computational and Biological Learning
Depositing User: Cron Job
Date Deposited: 07 Mar 2014 11:30
Last Modified: 25 Aug 2014 01:10
DOI: 10.1113/jphysiol.2005.090449

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