Document Type

Dissertation

Date of Degree

Spring 2016

Degree Name

PhD (Doctor of Philosophy)

Degree In

Integrative Physiology

First Advisor

Kelly J. Cole

Abstract

Motor learning is an important component of daily life: humans are constantly adjusting their movements and acquiring new skills in order to meet the demands of their environment. Motor learning also contributes to neurorehabilitation, so it is therefore important to understand the neural mechanisms underlying motor learning so that these mechanisms can be exploited to promote neurorehabilitation after central nervous system injury. This dissertation focuses on three distinct methods of improving motor learning in healthy adults. In Chapter 2, we tested the effects of perturbation schedule on retention of a locomotor adaptation. The results of this work demonstrated that introducing a perturbation slowly and incrementally versus introducing a perturbation abruptly produces similar behavioral expression of locomotor memories across days. In Chapter 3, we tested whether administering 200 mg of caffeine immediately after practicing a novel motor skill enhances retention of that skill 24 hours later. However, we found that post-practice caffeine administration did not significantly improve retention of the motor skill. In combination with previous reports, these results suggest that the effects of post-practice caffeine administration are likely task-specific. In Chapter 4, we examined the interactions between hand use, practice-dependent plasticity and motor learning. We found that experimentally immobilizing the left hand for 8 hours facilitates subsequent practice-dependent changes in corticospinal excitability in a topographically-specific manner. In contrast, immobilization did not facilitate practice-dependent changes in TMS-evoked thumb movements, nor did it promote learning or retention of a ballistic motor skill. Although it is thought that practice-dependent changes in corticospinal excitability are an important and potentially causal contributor to motor memory, the results of this work indicate that experimentally enhancing practice-dependent changes in corticospinal excitability is not sufficient to promote motor learning. In sum, although none of the experimental interventions tested here substantially improved motor learning, these experiments highlight the influence of various mechanisms on motor learning in the intact nervous system.

Public Abstract

As humans, we are constantly adjusting our movements to better suit new circumstances (i.e., changing our gait pattern to walk on ice without falling) and acquiring new motor skills (i.e., learning to swing a golf club for the first time). These changes to our movements occur through a process called motor learning. The goal of this dissertation was to investigate methods of improving motor learning and memory in healthy adults so that eventually similar methods can be used to promote neurorehabilitation in individuals with neurological damage. We tested the effects of three different interventions on motor learning processes. First, we examined whether the method of introducing a change to someone’s walking pattern affects how well they remember that walking pattern the next day. Here, we found that how the change is introduced does not strongly modify the ability to remember the newly-learned walking pattern. Second, we tested whether administering caffeine immediately after learning a new motor skill improves memory of that skill 24 hours later. In this experiment, we found no evidence that caffeine facilitated memory of the newly-learned skill. Third, we examined the impact of short-term immobilization on motor learning, as well as changes in brain function that are thought to be critical for motor learning and memory. Although immobilization facilitated learning-associated changes in brain function, it did not improve motor learning or memory. Overall, this dissertation sheds new light on how the brain learns to adjust well-learned movement patterns and to acquire new motor skills.

Keywords

publicabstract, adaptation, memory, motor learning, neurophysiology, plasticity

Pages

xiii, 116

Bibliography

101-116

Copyright

Copyright 2016 Sara Jeanne Hussain

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