Two Functionally Different Synergies During Arm Reaching Movements
Involving the Trunk.
Ma, S., and A. G. Feldman.
Department of Exercise Science, Concordia University, Montreal, Quebec H4B
1R6; Centre de Recherche, Institut de r[acute]eadaptation de Montr[acute]eal,
Montr[acute]eal, Qu[acute]ebec H3S 2J4; and Institut de g[acute]enie
biom[acute]edical, Universit[acute]e de Montr[acute]eal,
Montr[acute]eal, Qu[acute]ebec H3C 3J7, Canada.
APStracts 2:0049N, 1995.
SUMMARY AND CONCLUSIONS
1. To address the problem of the coordination of a redundant number of
degrees of freedom in motor control, we analyzed the influence of voluntary
trunk movements on the arm endpoint trajectory during reaching. 2. Subjects
made fast noncorrected planar movements of the right arm from a near to a far
target located in the ipsilateral work space at a 45 degrees angle to the
sagittal midline of the trunk. These reaching movements were combined with a
forward or a backward sagittal motion of the trunk. 3. The direction,
positional error, curvature, and velocity profile of the endpoint trajectory
remained invariant regardless of trunk movements. Trunk motion preceded
endpoint motion by _175 ms, continued during endpoint movement to the target,
and outlasted it by 200 ms. This sequence of trunk and arm movements was
observed regardless of the direction of the endpoint trajectory (to or from
the far target) or trunk movements (forward or backward). 4. Our data imply
that reaching movements result from two control synergies: one coordinates
trunk and arm movements leaving the position of the endpoint unchanged, and
the other produces interjoint coordination shifting the arm endpoint to the
target. The use of functionally different synergies may underlie a solution
of the redundancy problem.
Received 24 October 1994; accepted in final form 26 January 1995.
APS Manuscript Number J661-4.
Article publication pending J. Neurophysiol.
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 3 April 1995.