MOTOR LEARNING BY FIELD APPROXIMATION

We investigated how human subjects adapt to forces perturbing the moti on of their arms. We found that this kind of learning is based on the capacity of the central nervous system (CNS) to predict and therefore to cancel externally applied perturbing forces. Our experimental resul ts indicate: (i) that the ability of the CNS to compensate for the per turbing forces is restricted to those spatial locations where the pert urbations have been experienced by the moving arm. The subjects also a re able to compensate for forces experienced at neighboring workspace locations. However, adaptation decays smoothly and quickly with distan ce from the locations where disturbances had been sensed by the moving limb. (ii) Our experiments also show that the CNS builds an internal model of the external perturbing forces in intrinsic (muscles and/or j oints) coordinates.