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: 96/3/1124    most recent 01152.2005v1 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 PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Ustinova, K. I. Articles by Levin, M. F. Search for Related Content PubMed PubMed Citation Articles by Ustinova, K. I. Articles by Levin, M. F.

Central Resetting of Neuromuscular Steady States May Underlie Rhythmical Arm Movements

¹School of Rehabilitation and ²Department of Physiology, University of Montreal, Montreal, Quebec, Canada; ³School of Physical and Occupational Therapy, McGill University, Montreal, Quebec, Canada; ⁴Jewish Rehabilitation Hospital Research Site of the Centre for Interdisciplinary Research in Rehabilitation (CRIR), Montreal, Quebec, Canada; and ⁵Institute of Neurology, Russian Academy of Medical Sciences, Moscow, Russia

Submitted 1 November 2005; accepted in final form 8 May 2006

Changing the steady-state configuration of the body or its segments may be an important function of central pattern generators for locomotion and other rhythmical movements. Thereby, muscle activation, forces, and movement may emerge following a natural tendency of the neuromuscular system to achieve the current steady-state configuration. To verify that transitions between different steady states occur during rhythmical movements, we asked standing subjects to swing one or both arms synchronously or reciprocally at 0.8 Hz from the shoulder joints. In randomly selected cycles, one arm was transiently arrested by an electromagnetic device. Swinging resumed after some delay and phase resetting. During bilateral swinging, the nonperturbed arm often stopped before resuming swinging at a position that was close to either the extreme forward or the extreme backward arm position observed before the perturbation. Oscillations usually resumed when both arms arrived at similar extreme positions when a synchronous bilateral pattern was initially produced or at the opposite positions if the initial pattern was reciprocal. Results suggest that a central generator controls both arms as a coherent unit by producing transitions between its steady state (equilibrium) positions. By controlling these positions, the system may define the spatial boundaries of movement. At these positions, the system may halt the oscillations, resume them at a new phase (as observed in the present study), or initiate a new motor action. Our findings are relevant to locomotion and suggest that walking may also be generated by transitions between several equilibrium configurations of the body, possibly accomplished by modulation and gating of proprioceptive reflexes.