Biomedical Engineering Ph.D. Thesis Defense

Date: Monday, March 25, 2019
Time: 2:00pm-3:00pm
Location: HSRB Auditorium
Bluejeans: https://bluejeans.com/216663345 

Advisor:        
Lena Ting, PhD

Committee Members:
Greg Hajcak, PhD (Florida State University)
Lucas Mckay, PhD
Michael Borich, PhD
Dieter Jaeger, PhD
Tim Cope, PhD
Thomas Wichmann, MD

Title: Perturbation-evoked cortical responses are associated with balance ability in healthy young adults and in older adults with Parkinson’s disease

Abstract:

Balance and cognitive impairments negatively impact quality of life in old age and in Parkinson’s disease (PD) and are associated through unknown mechanisms. Although it is possible that the associated decline in balance and cognitive abilities is due to parallel age-related decline in both domains, evidence that combined cognitive and motor interventions provide synergistic benefits to balance ability suggests the existence of a therapeutic target at the intersection of balance and cognitive dysfunction. Measuring brain activity during reactive balance recovery may yield insight into the relationship between balance and cognitive function, facilitating the development of better treatment strategies. Electroencephalography (EEG) recordings show that sudden perturbations to standing balance reliably evoke a cortical N1 response localized to the supplementary motor area. Although the function of this cortical response is unknown, its amplitude is associated with sensory activity related to the balance disturbance and it is also influenced by cognitive processes, including attention, perceived threat, and predictability. As such, this cortical response may reflect a site of interaction between balance and cognitive function, which we want to understand in the context of balance impairment. While relatively little is known about the cortical N1 response, it resembles a widely studied cognitive marker called the error-related negativity (ERN), which reflects recognition of a self-committed error, and relates to action correction. Motivated by the similarities between these two responses, and by the fact that ERN amplitudes are smaller in people with PD, this project investigates the cortical N1 response in PD in relation to balance and cognitive abilities, and also in relation to the ERN. First, I show in healthy young adults (HYA) that cortical N1 responses are weakly influenced by perturbation acceleration, but that much greater variation in cortical N1 amplitudes between subjects is associated with balance ability. Then I show that perturbation-evoked cortical responses in older adults with and without PD contain two distinct component peaks, with the first component peak associated with cognitive but not balance ability, and the second component peak associated with balance but not cognitive ability. This double dissociation suggests that perturbation-evoked cortical responses may contain distinct biomarkers for balance and cognitive function in older adults with and without PD, which may facilitate future studies into the relationship between balance and cognitive impairments for the development of better rehabilitation strategies. Finally, I compare amplitudes of perturbation-evoked cortical responses to ERN amplitudes within HYA and within older adults with and without PD, showing that the relationship between these responses differs across the populations, suggesting that the mechanisms underlying these responses may differ.