Control of balance during walking in individuals with Parkinson's disease
Date
2024
Authors
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Publisher
University of Delaware
Abstract
Falls are a major cause of injury and death in individuals with Parkinson’s disease. Parkinson’s disease (PD) is a neurodegenerative disorder that affects older adults. PD is caused by the degeneration of neurons in the substantia nigra pars compacta and results in reduced dopamine production. Reduced dopamine levels cause neural dysfunction which can lead to the four cardinal motor symptoms of PD, tremor, bradykinesia, rigidity, and postural instability. Additionally, individuals with PD have difficulty processing and integrating information from three key senses needed for balance control, vision, vestibular, and proprioception. Due to deficits in motor function and sensory processing falls may occur. Currently there is no cure for PD, therefore it is critical to understand the underlying motor and neural processes related to walking balance control in individuals with Parkinson’s disease to develop effective interventions related to falls. The objective of this dissertation is to investigate how individuals with PD use either visual or vestibular information to control their balance during walking and the associated neural processes. ☐ Older adults rely more on visual information for balance control than young adults. It is also known that our visual system declines with age. Yet it is unknown if the balance deficits present in individuals with PD are due to the effects of aging or the disease. In Aim 1, we used visual perturbations to understand how individuals with and without PD utilize visual information for walking balance control. We found no significant differences of overall center of mass displacement between groups following the visual perturbation. However, we did observe that individuals with PD took a smaller step following the visual perturbation than older adults, thus resulting in a narrower base of support. These findings suggest that individuals with PD are able to process visual information to the same degree as older adults, thus the balance deficits may be a motor execution problem exhibited by individuals with PD taking a smaller step. ☐ In addition to visual information, vestibular feedback is also crucial to balance control. In Aim 2, we used vestibular perturbations to understand how individuals with and without PD utilize vestibular information for walking balance control. We found that following a vestibular perturbation, individuals with PD had similar center of mass displacements as individuals without PD. While the PD group showed a similar magnitude of center of mass response, there was a temporal difference. Individuals with PD reached their peak center of mass displacement later than older adults. We found individuals with PD had reduced balance mechanism responses than older adults. In other words, individuals with PD showed smaller ankle roll, step placement, and push off than older adults without PD. The timing delay suggest a vestibular processing deficit while the diminished balance mechanism responses suggest a motor execution deficit in older adults with PD. ☐ Quantifying the balance mechanisms is a neuromechanical approach to understanding the neural processes related to balance control. For the 3rd Aim, we conducted a pilot study which incorporated neural imaging techniques in addition to our neuromechanical outcome measures to gain a deeper understanding of the underlying neural processes related to walking balance control in PD. We investigated resting state functional connectivity maps in individuals with and without PD and compared the imaging results to a walking task performed immediately after the brain image acquisition. We showed that while individuals with PD had higher functional connectivity scores between the sensorimotor region and the left secondary visual cortex, they were less affected by the visual stimulus during the walking task compared to individuals without PD. ☐ Overall, we found neuromechanical and neurological differences between individuals with and without PD that may explain the diminished balance control present in PD.
Description
Keywords
Parkinson's disease, Walking balance control, Neurodegenerative disorder, Older adults