Path Curvature in Workspace and in Joint Space: Evidence for Coexisting Coordinative Rules in Aiming

in Motor Control
Restricted access

In this study we tried to establish whether point-to-point aiming movements are planned in workspace, joint space, or both. Eight right-handed subjects performed horizontal, vertical, and diagonal aiming movements on a transversal plane. Movements were performed at several speeds. Curvature variations of the hand and corresponding joint-space paths were investigated as a function of position, direction, and speed. Straightness of hand paths predominated for vertical movements but was systematically violated for horizontal and top-right to bottom-left movements. Furthermore, the hand-path curvature of the latter movements increased with speed. Joint-space paths showed more deviation from a straight line than hand paths except for top-left to bottom-right movements in which the paths were equally curved. A comparison of normalized path curvatures at the hand and joint level indicated that in aiming, the coordinative rule of straight-line production seems to apply to both workspace and joint-space planning. The present findings confirm Kawato's (1996) views that optimization processes operate concurrently at the two control levels of arm-trajectory formation under study.

The authors are with the Nijmegen Institute for Cognition and Information, PO Box 9104, 6500 HE Nijmegen, The Netherlands.

All Time Past Year Past 30 Days
Abstract Views 994 326 63
Full Text Views 0 0 0
PDF Downloads 0 0 0