HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Full Text (PDF) All Versions of this Article: 99/2/1032    most recent 01110.2007v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Web of Science (10) Citing Articles via Google Scholar Google Scholar Articles by Welch, T. D. J. Articles by Ting, L. H. Search for Related Content PubMed PubMed Citation Articles by Welch, T. D. J. Articles by Ting, L. H.

REPORT

A Feedback Model Reproduces Muscle Activity During Human Postural Responses to Support-Surface Translations

The Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, Georgia

Submitted 5 October 2007; accepted in final form 16 December 2007

Although feedback models have been used to simulate body motions in human postural control, it is not known whether muscle activation patterns generated by the nervous system during postural responses can also be explained by a feedback control process. We investigated whether a simple feedback law could explain temporal patterns of muscle activation in response to support-surface translations in human subjects. Previously, we used a single-link inverted-pendulum model with a delayed feedback controller to reproduce temporal patterns of muscle activity during postural responses in cats. We scaled this model to human dimensions and determined whether it could reproduce human muscle activity during forward and backward support-surface perturbations. Through optimization, we found three feedback gains (on pendulum acceleration, velocity, and displacement) and a common time delay that allowed the model to best match measured electromyographic (EMG) signals. For each muscle and each subject, the entire time courses of EMG signals during postural responses were well reconstructed in muscles throughout the lower body and resembled the solution derived from an optimal control model. In ankle muscles, >75% of the EMG variability was accounted for by model reconstructions. Surprisingly, >67% of the EMG variability was also accounted for in knee, hip, and pelvis muscles, even though motion at these joints was minimal. Although not explicitly required by our optimization, pendulum kinematics were well matched to subject center-of-mass (CoM) kinematics. Together, these results suggest that a common set of feedback signals related to task-level control of CoM motion is used in the temporal formation of muscle activity during postural control.

This article has been cited by other articles:

				S. Kim, F. B. Horak, P. Carlson-Kuhta, and S. Park Postural Feedback Scaling Deficits in Parkinson's Disease J Neurophysiol, November 1, 2009; 102(5): 2910 - 2920. [Abstract] [Full Text] [PDF]

				H. J. Chiel, L. H. Ting, O. Ekeberg, and M. J. Z. Hartmann The Brain in Its Body: Motor Control and Sensing in a Biomechanical Context J. Neurosci., October 14, 2009; 29(41): 12807 - 12814. [Abstract] [Full Text] [PDF]

				A. D. Goodworth and R. J. Peterka Contribution of Sensorimotor Integration to Spinal Stabilization in Humans J Neurophysiol, July 1, 2009; 102(1): 496 - 512. [Abstract] [Full Text] [PDF]

				T. D. J. Welch and L. H. Ting A Feedback Model Explains the Differential Scaling of Human Postural Responses to Perturbation Acceleration and Velocity J Neurophysiol, June 1, 2009; 101(6): 3294 - 3309. [Abstract] [Full Text] [PDF]

				I. D. Loram, M. Lakie, and P. J. Gawthrop Visual control of stable and unstable loads: what is the feedback delay and extent of linear time-invariant control? J. Physiol., March 15, 2009; 587(6): 1343 - 1365. [Abstract] [Full Text] [PDF]