Citation

Malone LA, Bastian AJ, Torres-Oviedo G. J. Neurophysiol. 2012; 108(2): 672-683.

Affiliation

Kennedy Krieger Insitute.

Copyright

(Copyright © 2012, American Physiological Society)

DOI

10.1152/jn.00391.2011

PMID

22514294

Abstract

Walking is a complex behavior for which the healthy nervous system favors a smooth, symmetric pattern. However, people often adopt an asymmetric walking pattern after neural or biomechanical damage (i.e. they limp). To better understand this aberrant motor pattern and how to change it, we have studied walking adaptation on a split-belt perturbation where one leg is driven to move faster than the other. Initially, healthy adult subjects take asymmetric steps on the split-belt treadmill, but within ten to fifteen minutes people adapt to re-establish walking symmetry. Which of the many walking parameters does the nervous system change in order to restore symmetry during this complex act (i.e., what motor mappings are adapted to restore symmetric walking in this asymmetric environment)? Here we found two parameters that met our criteria for adaptive learning. The first is a temporal motor output consisting of the duration between heel-strikes of the two legs (i.e. "when" the feet land). The second is a spatial motor output, related to the landing position of each foot relative to one another (i.e. "where" the feet land). We found that when subjects walk in an asymmetric environment, they smoothly change their temporal and spatial motor outputs to restore temporal and spatial symmetry in the inter-limb coordination of their gait. These changes in motor outputs are stored and have to be actively de-adapted. Importantly, the adaptation of temporal and spatial motor outputs is dissociable since subjects were able to adapt their temporal motor output without adapting the spatial one. Taken together, our results suggest that the temporal and spatial control for symmetric gait can be adapted separately, and therefore we could potentially develop interventions targeting either temporal or spatial walking deficits.

Language: en