Learning to Perform a Novel Movement Pattern Using Haptic Guidance: Slow Learning, Rapid Forgetting, and Attractor Paths

J Liu,J.L Emken,S.C Cramer,D.J Reinkensmeyer

doi:10.1109/icorr.2005.1501046

Abstract

Mechanical guidance is a common technique to teach patients desired movement patterns during motor rehabilitation, but little is known about the motor learning processes involved with this technique. In this study we examined how well unimpaired subjects could learn to trace a novel path after they practiced it with mechanical guidance from a robot. The form of haptic guidance used was a virtual channel that constrained the hand to follow the desired path (a snake-like curve). Subjects substantially improved their ability to trace the path following practice with haptic guidance, relative to their performance following an initial visual demonstration. They slowly improved their performance with more haptic training. However, when asked to reproduce the path repeatedly, their performance degraded over the course of a few trials. The tracing errors were not random, but instead were consistent with a systematic evolution toward another path, as if being drawn to an attractor path. These results suggest that haptic demonstration can improve short-term performance of a novel desired trajectory. However, in the short term, the motor system is inclined to repeat its mistakes following just a few movements without guidance.

Highlights

Robotic devices are increasingly being used as tools for movement training following neurologic injury [1,2,3]
Unclear what the advantages of mechanical guidance are compared to other movement training techniques, including unassisted practice [6], error-amplification techniques [9, 10] and visual demonstration [11]
Experiencing the trajectory with vision of arm for just one training cycle significantly reduced the tracing error compared to the tracing error following visual demonstration (p < 0.0001)

Summary

INTRODUCTION

Robotic devices are increasingly being used as tools for movement training following neurologic injury [1,2,3]. They are candidates as tools for training skillful movements, such as those required for surgery or athletics. The predominate training paradigm that has been explored so far in rehabilitation is mechanical guidance; that is, the robotic device physically guides the patient’s limbs through a desired trajectory. Unclear what the advantages of mechanical guidance are compared to other movement training techniques, including unassisted practice [6], error-amplification techniques [9, 10] and visual demonstration [11]. One way that mechanical guidance might be beneficial is in demonstrating a novel, complex desired trajectory.

Experimental Protocol

Path tracing accuracy improved following haptic guidance

DISCUSSION