<p> Humans use their upper limbs for interacting with many objects, tools and loads. It is crucial to maintain arm stability during these interactions, which can be done by regulating the impedance of the arm through a combination of feedforward and feedback neural mechanisms. Feedback tuning, in particular, provides an efficient and task-specific means for impedance control. However, the factors that drive feedback tuning remain unclear. In addition, it is uncertain how feedback mechanisms may contribute differently to impedance control in the dominant versus nondominant arm, which frequently perform different types of tasks. The goal of this dissertation was to examine mechanisms of impedance control in either arm, using various experimental methods to examine neuromuscular control during single-joint posture and movement. Firstly, we examined attention as a factor that may be crucial for feedback tuning in either arm. By comparing feedback responses evoked under different attention conditions, we determined that attention alone is not sufficient for feedback tuning, indicating that interaction with destabilizing dynamics is key for task-specific feedback tuning. Secondly, we examined differences between the dominant and nondominant arm in terms of feedback tuning during a postural task. By comparing feedback responses evoked when postural stability in each arm was challenged, we showed that feedback tuning contributes equally to either arm during posture. Finally, we investigated the idea that inter-arm differences in impedance control may only manifest when switching between movement and posture. This was accomplished by comparing the contributions of feedforward and feedback mechanisms during unperturbed, point-to-point reaching in either arm. The results indicate that the nondominant arm demonstrates greater reliance on impedance control and feedback mechanisms during reaching, but that prior training with the dominant arm can reduce this bias.</p>
| Identifer | oai:union.ndltd.org:PROQUEST/oai:pqdtoai.proquest.com:3741391 |
| Date | 23 December 2015 |
| Creators | Walker, Elise Hope Eccles |
| Publisher | Northwestern University |
| Source Sets | ProQuest.com |
| Language | English |
| Detected Language | English |
| Type | thesis |
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