Title: Scaling and adaptation of dynamic balance responses in Parkinson’s disease
Thesis Supervisor: Dr. Mark Carpenter
Committee members: Dr. Tim Inglis, Dr. Romeo Chua
Defence Chair: Dr. Hyosub Kim
Abstract:
Parkinson’s disease (PD) is a neurodegenerative disease characterized by tremor, bradykinesia, rigidity, and postural instability. As postural instability worsens with disease progression, this can result in falls, leading to loss of independence and quality of life. Previous research on PD has attributed dynamic balance deficits to ineffective sensory integration, abnormal generation of motor patterns, and excessive background muscle tone, however further research is needed to investigate the dynamic characteristics of responses to balance perturbations. Therefore, this thesis had two goals: (1) characterize amplitude and scaling of dynamic balance responses during transient perturbations in PD and (2) characterize the effect of sudden visual changes on dynamic balance responses during continuous surface tilt perturbations in PD.
On a multidirectional tilting platform, 13 PD patients in their best clinical “ON”-medication state and 15 healthy controls completed a series of randomized anteroposterior (AP) transient perturbations at 2.5°, 5°, and 7.5° amplitudes. Participants then completed a series of continuous AP perturbations (either sine or sum of sines rotations) with sudden visual changes throughout trials. Results showed differences between groups demonstrated by PD patients having increased balance correcting response amplitudes and increased scaling of muscle responses. Additionally, there were various effects of sudden visual changes across groups during continuous perturbations, with correlations between symptom severity in PD and longer delays in postural adaptation to these visual changes. The findings from this study provide novel insight into the scaling and adaptation of balance responses using dynamic posturography in PD.