ON THE FORM OF THE INTERNAL MODEL FOR REACHING

We investigated, by using simulations, possible mechanisms responsible for the errors in the direction of arm movements exhibited by deaffer ented patients. Two aspects of altered feedforward control were evalua ted: the inability to sense initial conditions and the degradation of an internal model. A simulation which assumed no compensation for vari ations in initial arm configuration failed to reproduce the characteri stic pattern of errors. In contrast, a simulation that assumed random variability in the generation of joint torque resulted in a distributi on of handpaths which resembled some aspects of the pattern of errors exhibited by deafferented patients.