IMPAIRMENTS IN THE STABILITY OF HAND FUCTION IN PATIENTS WITH NEUROLOGICAL DISORDERS
Open Access
- Author:
- Jo, Hang Jin
- Graduate Program:
- Kinesiology
- Degree:
- Doctor of Philosophy
- Document Type:
- Dissertation
- Date of Defense:
- May 04, 2016
- Committee Members:
- Mark Latash, Dissertation Advisor/Co-Advisor
Mark Latash, Committee Chair/Co-Chair
Xuemei Huang, Outside Member
Robert L Sainburg, Committee Member
Kristina A Neely, Committee Member - Keywords:
- Synergy
Hand
Prehension
Uncontrolled Manifold Hypothesis
Parkinson's disease - Abstract:
- The concept of synergy provides a theoretical framework for movement stability resulting from the neural organization of elements that contribute to salient performance variables. Analysis of synergies has been performed within the uncontrolled manifold hypothesis, in which variance is decomposed into two components depending on whether it affects task performance or not. Then, the two components are reduced to a single index reflecting the relative amount of two variance components; this index is typically used as a synergy index. The method has proven to be able to quantify synergies in a variety of elemental spaces for a variety of tasks. In this dissertation, a series of studies exploring synergies stabilizing the hand action in various subpopulations are presented. Subpopulations include patients with Parkinson’s disease, multiple sclerosis, cortical stroke, and healthy controls. The application of the concept of synergy to patient groups has allowed quantifying aspects of impairments related to movement stability and agility and also provided insights into neural mechanisms of synergic control. The evidence presented in the dissertation has led to the following main conclusions. First, impaired control of movement stability is commonly seen in persons with impairments in subcortical brain structures. The impairments are seen as low synergy indices during steady states of performance and delayed/reduced drop in the synergy indices before quick action (low anticipatory synergy adjustments). Second, these two components of the impairments in the control of stability may have distinct neurophysiological mechanisms and they could be selectively involved in different disorders. The results consistently suggest subcortical loops as being crucial for high stability of task performance. Third, the changes in synergy indices could be seen at the early stages of the PD and even in subclinical stages of disorder involving the basal ganglia, when traditional clinical examination fails to show any impairment. Lastly, changes in motor synergies are sensitive to treatment in PD patients. These features potentially make synergy indices a powerful tool to objectively quantify the impairments of motor symptoms and also a useful biomarker for early detection of motor changes.