Estimation of visual feedback contribution to limb stiffness in visuomotor control

Abstract

The purpose of this work was to investigate contribution of a visual feedback system to limb stiffness. It is difficult to differentiate the visual component from others out of measured data obtained by applying a force perturbation, which is required to estimate stiffness,. In this study, we proposed an experimental procedure consisted of a pair of tasks to investigate the visual feedback component, and showed it as end-point stiffness ellipses at several timings of a movement. In addition, we carried out a numerical simulation of the movement with the perturbation in according with a framework of optimal feedback control model. As results, long axes of the stiffness ellipses of the visual component were modulated to the movement directions and the simulation showed that a positional feedback gain was exponentially increased toward a movement end. Consequently, the visual feedback system is supposed to regulate compliance of a movement direction. © 2012 Springer-Verlag.