Somatosensory Contribution to the Initial Stages of Human Motor Learning.
The early stages of motor skill acquisition are often marked by uncertainty about the sensory and motor goals of the task, as is the case in learning to speak or learning the feel of a good tennis serve. Here we present an experimental model of this early learning process, in which targets are acquired by exploration and reinforcement rather than sensory error. We use this model to investigate the relative contribution of motor and sensory factors to human motor learning. Participants make active reaching movements or matched passive movements to an unseen target using a robot arm. We find that learning through passive movements paired with reinforcement is comparable with learning associated with active movement, both in terms of magnitude and durability, with improvements due to training still observable at a 1 week retest. Motor learning is also accompanied by changes in somatosensory perceptual acuity. No stable changes in motor performance are observed for participants that train, actively or passively, in the absence of reinforcement, or for participants who are given explicit information about target position in the absence of somatosensory experience. These findings indicate that the somatosensory system dominates learning in the early stages of motor skill acquisition.


CONCLUSIONS
The research focuses on the initial stages of human motor learning, introducing a new experimental model that closely approximates the key features of motor learning outside of the laboratory. The finding indicates that it is the somatosensory system rather than the motor system that dominates learning in the early stages of motor skill acquisition. This is important given that most of our computational models of motor learning are based on the idea that learning is motoric in origin. This is also a valuable finding for rehabilitation of patients with limited mobility as it shows that reinforcement in conjunction with passive movement results in benefits to motor learning that are as great as those observed for active movement training.
Department of Psychology, McGill University, Montreal, Quebec H3A 1B1, Canada, and.
Nicolò F
NF
Bernardi
Department of Psychology, McGill University, Montreal, Quebec H3A 1B1, Canada, and.
Mohammad
M
Darainy
Department of Psychology, McGill University, Montreal, Quebec H3A 1B1, Canada, and Haskins Laboratories, New Haven, Connecticut 06511 david.ostry@mcgill.ca.
David J
DJ
Ostry
D000293:Adolescent; D000704:Analysis of Variance; D005260:Female; D006801:Humans; D007600:Judgment; D007858:Learning / Q000502:physiology*; D008297:Male; D009068:Movement / Q000502:physiology*; D016059:Range of Motion, Articular / Q000502:physiology*; D012054:Reinforcement, Psychology; D013003:Somatosensory Cortex / Q000502:physiology*; D055815:Young Adult
motor learning; motor skill learning; passive movements; reinforcement; somatosensory perception