Robotic Teaching By Exploiting the Nervous System's Adaptive Mechanisms

We tested the idea of teaching arm movements implicitly, based on recent studies of adaptive control. Eight subjects were repeatedly exposed to predetermined training forces during movement so they would develop an expectation and cancel them out. Forces were unexpectedly removed to cause a predictable after-effect. Forces were designed so that a "desired" movement would result as this after-effect. This method does not require any explicit instructions about the desired movement. Results showed a significant shift of trajectories toward the desired, although the after-effect washed out following the removal of the forces in about 75 movements. This approach may be effective for teaching healthy movement patterns to brain injured patients because their movement alterations can be perceived as improvements.