The human hand is critically important for the performance of many activities of daily living. This dissertation used three human subject studies to investigate how different types of motor repetition interact with the process of sensorimotor adaptation and learning in complex dexterous manipulation tasks that depend on finger force control or bimanual coordination. Moreover, these investigations were conducted in both young adults (YA) and older adults (OA) to reveal the extent to which the process of aging may alter such interactions. In the first study, it was found that the repetition of simple ballistic force exertion allowed YA to better adapt to external mechanical perturbation with their dominant hand during fast object transport than the repetition of continuous movement. In contrast, OA were not differently affected by these two types of repetition training. In the second study, the effect of the same two repetition types on learning to perform an inverted pendulum balance task was examined. It was found that OA but not YA were able to balance the pendulum longer with the ballistic force repetition than the continuous movement repetition. In the last study, participants must move both hands to simultaneously follow moving targets. It was revealed that adaptation to unilateral visual or mechanical constraints was driven by the dominant hand in YA, but OA were not able to adapt to these constraints. Together with additional findings about balance control and visual attention, these results on the effect of motor repetition provide new insights into the mechanisms underlying sensorimotor learning, which will support future studies to improve the efficacy of neurorehabilitation for dexterous manual functions.
Qiushi Fu, Committee Chair.
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