How does the central nervous system use errors to optimize motor learning?

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Motor learning is the process by which we learn new, or improve the quality of previously learned, motor skills, like those used in sports or physical activities. There are two ways that motor learning happens: 1) we practice the `correct' movement, and this movement gets reinforced in our memories, or 2) we make errors during the movement and learn to correct these errors with practice. Errors can be caused by our own mistakes in planning or executing a movement, or can be caused by external forces outside of our bodies (e.g., practicing on a windy day when the wind knocks you off balance). Some researchers think that the source of the error (internal or external to our bodies) determines how we learn the motor skill. Hypothetically, if the source is internal, adaptations will generalize to many different situations, but if the source is external, we will only adapt in the environment where the error occurred; however, no one has directly tested this hypothesis. We also do not know how our brains determine if the error is internal or external. Additionally, the consequences of the motor error might influence how we adapt; if the error threatens our safety (e.g., could lead to an injury) then the adaptations might be stronger than if the error has little consequence. This research will determine how our brains use error to learn motor skills. We will conduct several experiments where participants will learn a novel balance skill. In these experiments, we will manipulate participants' knowledge about the source of motor errors (internal or external) and the consequences of errors (e.g., reward, `punishment', or no consequence). After practicing the balance skill, we will test how well participants perform on a similar balance task to see how well their learning generalizes. We expect that generalization of learning will be better when participants believe the source of the errors is internal (versus external), and when participants are `punished' for their errors (versus rewarded or receive no consequence). We will also determine which practice and participant characteristics influence participants' beliefs about the sources of errors and how well learning generalizes. We expect that people with an external locus of control (believe that events are outside their control) will be more likely to believe that errors come from an external source than those with an internal locus of control. We also expect that people who pay a lot of attention to their movements will be better able to determine the source of errors than those who do not. This work will improve our knowledge of how to use errors during practice to optimize motor learning. The findings can be used to help people who are learning new, or improving old, motor skills in sports, occupational, or rehabilitation settings. Of note, this work has the potential to reveal that optimal practice strategies may differ for different people depending on their individual characteristics.