Abstract
Many gait training programs are based on supervised learning principles: an individual is guided towards a desired gait pattern with directional error feedback. While this results in rapid adaptation, improvements quickly disappear. This study tested the hypothesis that a reinforcement learning approach improves retention and transfer of a new gait pattern. The results of a pilot study and larger experiment are presented. Healthy subjects were randomly assigned to either a supervised group, who received explicit instructions and directional error feedback while they learned a new gait pattern on a treadmill, or a reinforcement group, who was only shown whether they were close to or far from the desired gait. Subjects practiced for 10 min, followed by immediate and overnight retention and over-ground transfer tests. The pilot study showed that subjects could learn a new gait pattern under a reinforcement learning paradigm. The larger experiment, which had twice as many subjects (16 in each group) showed that the reinforcement group had better overnight retention than the supervised group (a 32% vs. 120% error increase, respectively), but there were no differences for over-ground transfer. These results suggest that encouraging participants to find rewarding actions through self-guided exploration is beneficial for retention.
Highlights
Restoration of a healthy walking pattern is a major goal of neurological rehabilitation
Subjects A total of 16 healthy young adults were recruited. They were randomly assigned to either a supervision group (2 males/5 females; age: 22.9 ± 1.6 years; height: 166 ± 7.4 cm; weight: 67.5 ± 14.9 kg), in which the visual feedback was supervisory in nature, or a reinforcement group (3 males/4 females; age: 22.8 ± 0.7 years; height: 170.5 ± 9.3 cm; weight: 70.1 ± 11.2 kg), in which the visual feedback consisted of non-directional error feedback
Both groups improved their task performance with practice, retained their skill in the immediate retention test, and were able to transfer the learned gait pattern to an over-ground walking context in the immediate transfer test. Both retention and transfer became worse, but it appeared that the supervision group may have lost more of their skill compared to the reinforcement group
Summary
Restoration of a healthy walking pattern is a major goal of neurological rehabilitation. To facilitate this process, visual cues and manual or robotic assistance can be provided, which provides patients with feedback about their performance. Motor learning paradigms can be placed along a continuum based on the guidance provided by a human or machine. Many current gait training approaches fall heavily on one side of this continuum, under the umbrella of supervised learning. In such approaches, either a human or machine acts as a supervisor that guides a patient into a desired gait pattern. Feedback provided typically includes information about error magnitude and direction (i.e., vector-based), and can be provided via visual or haptic (e.g., guidance forces) sensory modalities
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