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Date of Award
Doctor of Philosophy (PhD)
Action observation has promise to expand therapy options in physical therapy to promote motor rehabilitation and recovery. Previous observation studies have found that action observation can facilitate motor learning: people are able to pick up context-specific cues from others’ movements to adapt to a novel mechanical environment. More specifically, an hour of observational learning reduced kinematic errors and produced adaptive changes in predictive limb control, similar to changes induced by physical practice. Here, we investigated action observation over several days, on a time scale more relevant for motor memory and rehabilitation. In particular we envision a first training day as analogous to a “clinic” visit, whereas subsequent observational training is analogous to “at-home” training through video viewing.
We trained 50 subjects in three experiments. On the first day of training, subjects learned a curl, viscous force field by one of the three training schedules: action observation, physical practice, or interleaved blocks of observation and physical practice. In action observation, subjects observed a film of another individual’s reaching movements in the force field in first-person perspective. In physical practice, subjects reached while holding a robotic arm that generated the same field. On subsequent days, in experimental conditions, subjects trained in a thirty-minute action observation session. In control conditions, subjects rested for thirty minutes while holding onto the robotic arm. To assess motor adaptation and learning, both within and across training days, we measured predictive force output using an error-clamped force channel, which provided positive reinforcement through straight movement toward the target, while enabling readout of predictive force generation throughout the trajectory. We calculated a scalar metric of motor memory by quantifying the velocity-dependent component of this predictive force, indicative of appropriate learning of the novel field.
Overall we found observation to boost motor memory effectively over several days. This retraining seemed effective following either initial observation or initial physical practice. We saw the most dramatic effects following initial combined training, perhaps due to heightened context or Hebb-like pairing of the modalities. Learning via observation therefore has basic science importance and clinical possibilities on time scales relevant to motor memory and recovery, beyond short-term motor adaptation. We conclude that observational training could be a powerful tool for rehabilitation and recovery, both within and between clinic visits.
Todd Braver, Sanmay Das, Daniel Moran, Lawrence Snyder
Available for download on Sunday, December 15, 2115