PhD Oral Exam - Averil Cathleen Parker, 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

Rhythmic Auditory Stimulation (RAS) is an intervention for gait rehabilitation in which individuals walk to an auditory cueing stimulus. While it is known that the cognitive contribution to walking increases with increasing age, the attentional demands of RAS are not well understood. Often isochronous metronome cues (i.e., with a constant inter-beat interval) are used during RAS. However, fluctuations in stride-to-stride intervals have a predictable (i.e. fractal) pattern over time, characterized by persistent long-range correlations. Walking to isochronous cues decreases long-range correlations in gait, making gait more random, while walking to a metronome with fractal-like fluctuations increases long-range correlations in gait. How cue types interact with beat perception is not known. This may be an important consideration, however, given that those with better beat perception tend to benefit more from RAS. Across the literature investigating RAS, data on middle-aged adults is lacking. We sought to better understand task parameters and individual characteristics which impact response to RAS. Paper 1 establishes the validity of footswitches to measure step-time parameters, compared against the gold standard electronic walkway. In Paper 2, young, middle-aged, and older adults walked to tones under increasing levels of task complexity. Middle-aged adults and a subgroup of older adults showed reduced step-time variability when walking to a simple beat. Among middle-aged adults, this effect was attenuated with increasing levels of task complexity. Additionally, stronger beat perception and auditory selective attention supported a positive response to cued walking. In Paper 3, young, middle-aged, and older adults walked to tones under increasing levels of attentional load. Tones were presented in isochronous and fractal rhythms. Walking to fractal cues increased long-range correlations relative to walking in silence. This increase was qualitatively greater among middle-aged adults. Walking to isochronous cues decreased long-range correlations relative to walking in silence, particularly for those with stronger beat perception. Attentional load did not modulate long-range correlations in gait. Taken together, this program of research showed dissociable effects of attentional load on the magnitude versus the pattern of variability in step-to-step fluctuations. We also highlighted important individual difference factors. These findings can help optimize RAS for gait rehabilitation.