Durability of Motor Learning by Observation
Abstract
Recent evidence suggests that neural representations of novel movement dynamics can be acquired by observing someone else experiencing them first-hand. Visual information about another person’s movement kinematics can be transformed into an adaptation of feedforward limb control for the observer; however, little is known about the durability of this adaptation. Despite the longevity of changes in the motor system being a defining characteristic of motor learning, studies to date have only examined observation-related effects shortly after observation has occurred, leaving unknown whether such effects are transient phenomena or products of learned, durable changes in neural systems. We measured human participants’ force generation patterns before and at various time points (1 minute – 24 hours) after they had either performed or observed movements that were perturbed by novel, robot-generated forces (i.e., a velocity-dependent force field). Like participants who had physically practiced, observers learned to predictively generate directionally- and temporally-specific compensatory forces during reaching. Although retention generally decayed with time, we found no evidence of an interaction between the effects of the passage of time and whether participants had performed or observed reaches in a force field, suggesting that the adaptation decayed similarly regardless of whether it was induced by observing someone else’s physical force field learning or feeling the force field for oneself. Notably, the adaptation of predictive limb control induced by observation was still detectable 24 hours later, demonstrating that visually-acquired representations of movement dynamics can be retained, and continue to influence behaviour, long after the initial training period is over. Our results suggest that observing can have lasting effects on the brain that are similar to those seen for physical practice.