Citation

Blanchette A, Moffet H, Roy JS, Bouyer LJ. J. Neurophysiol. 2012; 108(1): 275-284.

Affiliation

Universite Laval.

Copyright

(Copyright © 2012, American Physiological Society)

DOI

10.1152/jn.01098.2011

PMID

22496521

Abstract

Previous studies have shown that when subjects repeatedly walk in a perturbing environment, initial movement error becomes smaller, suggesting that retention of the adapted locomotor program occurred (learning). It has been proposed that the newly learned locomotor program may be stored separately from the baseline program. However, how locomotor performance evolves with repeated sessions of walking with the perturbation is not yet known. To address this question, 10 healthy subjects walked on a treadmill on 4 consecutive days. Each day, locomotor performance was measured using kinematics and surface EMGs before, during and after exposure to a perturbation produced by an elastic tubing that pulled the foot forward and up during swing, inducing a foot velocity error in the first strides. Initial movement error decreased significantly between Days 1 and 2 and then remained stable. Associated changes in Medial hamstring (MH) EMG activity stabilized only on Day 3, however. Aftereffects were present after perturbation removal, suggesting that daily adaptation involved central commands recalibration of the baseline program. Aftereffects gradually decreased across days but were still visible on Day 4. Separation between the newly learned and baseline programs may take longer than suggested by the daily improvement in initial performance in the perturbing environment, or may never be complete. These results therefore suggest that reaching optimal performance in a perturbing environment should not be used as the main indicator of a completed learning process, as central reorganization of the motor commands continues days after initial performance has stabilized.

Language: en