PhD Oral Exam - Rachel Downey, Psychology

When studying for a doctoral degree (PhD), candidates submit a thesis that provides a critical review of the current state of knowledge of the thesis subject as well as the student’s own contributions to the subject. The distinguishing criterion of doctoral graduate research is a significant and original contribution to knowledge.

Once accepted, the candidate presents the thesis orally. This oral exam is open to the public.

Abstract

This dissertation includes three studies that contribute to the cognitive and motor aging literature by exploring the processes and factors that underlie and mediate improvements in cognitive-motor dual-task (CMDT) performance following cognitive and physical interventions in older adults.

In Study 1, we examined the cognitive and physiological mechanisms underlying CMDT improvements following executive function training, aerobic exercise, and gross motor coordination training in cognitively unimpaired older adults. We found evidence that reduced metabolic energy expenditure, and improved task-switching abilities and inhibitory control may underlie improvements in CMDT following coordination training and executive function training, respectively. Additionally, lower baseline cognitive functioning was associated with greater improvements in cognitive dual-task performance.

In Study 2, we explored potential neuroplastic changes that may accompany or underlie improvements in CMDT following EF training in middle-aged and older adults. In general, we found that increased brain activity from single-task to dual-task predicted lower dual-task costs following executive function training, consistent with a neural compensation perspective. We further found larger magnitudes of improvement in dual-task cognition following training in participants with higher baseline cognitive functioning, whereas for dual-task gait, a greater magnitude of improvement was observed in middle-aged adults with higher cognitive status, and in older adults with lower cognitive functioning.

In Study 3, we explored the effects of auditory and cognitive capacity and biological sex on CMDT performance before and after exercise, alone or combination with cognitive training, in older adults with mild cognitive impairment. We found that lower hearing ability, particularly when compounded with poorer baseline cognitive functioning, was associated with a greater magnitude of dual-task gait improvements following multi-domain exercise and cognitive training, compared to participants with better hearing and cognitive functioning. We found differential effects of hearing capacity on training efficacy across males and females depending on the nature of the hearing measure (self-report vs. behavioural).

Taken together, these findings underscore the potential for targeted cognitive and physical interventions to mitigate age-related declines in CMDT. By identifying mechanisms of change and inter-individual differences that mediate training outcomes, this work informs the design of more effective, personalized strategies to promote healthy aging.