Master of Science
Gribble, Paul L.
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.
Summary for Lay Audience
Motor learning involves the brain learning what forces are required for movement. The forces that our muscles need to produce in order for us to move properly will inevitably change with growth, aging, injury, and in different environments. To preserve our ability to move despite these changes, sensory and motor areas of the brain must constantly be adapting. This adaptation is critical for maintaining motor control, but also underlies the learning of new and complex motor skills.
When we learn, the brain makes new connections that can change how it controls our bodies during movement. Although motor learning typically involves extensive physical practice, recent evidence suggests that the brain can also learn what forces are required for movement by observing the movements of others. This is interesting because forces are not things that can be seen. Information about the parts of another person’s movements that can be seen—like visible errors in where our bodies actually are, compared to where they are supposed to be—must be transformed into new connections in the brain that can then be used in the control of the observer’s movements. A defining characteristic of learning is that the changes in the brain that come with it need to be long-lasting. Research suggesting that observing can teach the brain about the forces required for movement has only ever looked at the effects of observation right after observing. As a result, it was not known whether previously described observation-driven changes in the brain were transient, or whether they might form stable memories that could influence motor control well past the end of the observation period. The present thesis addresses this question for the first time. Here we provide evidence that visually-induced changes in the neural circuitry involved in force control can be retained and influence behaviour 24 hours after observing someone else’s movement errors. We also find similarities in the stability of observation-related changes and physical practice-related changes over time. Our results suggest that observing can have lasting effects on the brain that are similar to those seen for physical practice.
Mangos, Natalia, "Durability of Motor Learning by Observation" (2022). Electronic Thesis and Dissertation Repository. 8694.
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