POSTURAL AND SYNERGIC CONTROL FOR THREE DIMENSIONAL MOVEMENTS OF REACHING
AND GRASPING.
Desmurget, Michel, Claude Prablanc, Yves Rossetti, Mohammad Arzi, Yves
Paulignan, and Christian Urquizar.
Vision et Motricit[acute]e, Institut National de la Sant[acute]e et de la
Recherche M[acute]edicale Unit[acute]e 94, 69500 Bron. France.
APStracts 2:0159N, 1995.
SUMMARY AND CONCLUSIONS
1. A fundamental question about motor control is related to the nature of the
representations used by the nervous system to program the movement.
Theoretically, arm displacement can be encoded either in task (extrinsic) or
in joint (intrinsic) space. 2. The present study investigated the organisation
of complex movements consisting of reaching and grasping a cylindrical object
presented along different orientations in space. In some trials object
orientation was suddenly modified at movement onset. 3. At a static level, the
final limb angles were highly predictable despite the wide range of possible
postures allowed by articular redundancy. Moreover, when object orientation
was unexpectedly modified at movement onset, the final angular configuration
of the limb was identical to that obtained when the object was initially
presented along the orientation reached after the perturbation. 4. At a
dynamical level, a generalized synergy was observed, and tight correlations
were noted between all joint angles implicated in the movement with the
exception of elbow flexion. For this joint angle, which did not vary
monotonically, strong partial correlation were however observed before and
after movement reversal. 5. These results suggest that natural movements are
mostly carried out in joint space by postural transitions.
Received 20 March 1995; accepted in final form 17 May 1995.
APS Manuscript Number J181-5.
Article publication pending J. Neurophysiol.
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 30 May 1995.