Does the oculo-manual co-ordination control system use an internal model of the arm dynamics?

The hypothesis that during self-moved target tracking, the eye-arm co-ordin ation control system uses an internal model of the arm dynamics was tested. The contribution of arm proprioception to this model was also assessed. Su bjects (nine healthy adults and one deafferented subject) were requested to make forearm movements and visually track an arm-driven target. Unexpected changes in mechanical properties of the manipulandum were used to modify t he dynamical conditions of arm movement, The smooth pursuit gain (SPG) was computed before and du ri ng the perturbation. Results showed a decrease of SPG during perturbation in control subjects only. We propose that an inter nal model of the arm dynamics may be used to co-ordinate eye and arm moveme nts, and arm proprioception may contribute to this internal model. (C) 1999 Elsevier Science Ireland Ltd. All rights reserved.