Vectorial coding of movement: vision, proprioception, or both?
Rossetti, Yves, Michel Desmurget, Claude Prablanc.
Vision et Motricite, I.N.S.E.R.M. Unit[acute]e 94, 16 avenue doyen Lepine,
69500 Bron France.
APStracts 2:0119N, 1995.
SUMMARY AND CONCLUSIONS
Subjects were asked to point toward visual targets without visual reafference
from their moving hand in two conditions. In both conditions their pointing
fingertip was viewed only prior to movement onset. In one condition, their
pointing fingertip was viewed through prisms that created a visual
displacement, but without altering the view of the target. In another
experimental condition, vision of the fingertip was not displaced. Comparison
of these two conditions showed that virtually shifting finger position prior
to movement through prisms induced a pointing bias in the direction opposite
to the shift. The extent of this pointing bias was about one third of the
prismatic shift applied to the fingertip. Analysis of movement initial
direction demonstrated that it was also less deviated than predicted from the
prismatic shift. In addition, the reaction time and movement time of the
reaching movement were increased. This result is interpreted in the framework
of the vectorial coding of reaching movement. Proprioception and vision
provide two possible sources of information about initial hand position, i.e.
the origin of the movement vector. The question remains, how these two sources
of information interact in specifying initial hand position when they are
simultaneously available. Our results are thus discussed with respect to a
visual-to-visual movement vector hypothesis, and a proprioceptive-to-visual
vector hypothesis. It is argued that the origin of the putative movement
vector is encoded by weighted fusion of the visual and the proprioceptive
information about hand initial position.
Received 28 October 1994; accepted in final form 6 April 1995.
APS Manuscript Number J678-4.
Article publication pending J. Neurophysiol.
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 1 May 1995.