Evaluating complex walking in aging and neurological disease : from motor behavior to brain activity

<p dir="ltr"><b>Aim</b>: To develop and validate a measurement protocol for evaluating cognitive-motor performance during complex walking in younger adults, older adults and people with Parkinson's disease, as well as to use this protocol to evaluate the effect of Parkinson's disease on this ability and explore factors of complex walking performance.</p><p dir="ltr"><b>Methods</b>: This thesis is composed of four papers investigating (1) feasibility of the pro- tocol, (2) validation of the protocol, and (3) evaluation and exploration of cognitive-motor performance during complex walking. A block-based complex walking protocol was used to assess cognitive-motor performance based around a straight walking task, a navi- gated walking task, and an auditory Stroop task. Functional near-infrared spectroscopy was used to measure prefrontal cortex activity, and inertial sensors were used to obtain spatiotemporal gait parameters. Clinical tests of balance and disease severity were per- formed, and neuropsychological and other individual factors were assessed. Scientific and process feasibility was evaluated in 19 healthy individuals. Preregistered validation hypotheses were tested in 133 participants to determine whether observed functional near-infrared spectroscopy responses reflected cognitive-motor demands rather than confounding factors. The thesis also tested the assumption that compensatory pre- frontal activity occurs to compensate for a loss of gait automaticity, quantified primarily using step time variability. Additionally, patterns of behavioral performance during nav- igated walking were explored using data-driven clustering methods, and clusters were characterized using demographic, task performance, and neuropsychological measures.</p><p dir="ltr"><b>Results</b>: The protocol was found to be feasible from a process and scientific feasibility perspective, and functional near-infrared spectroscopy observations were attributed to executive-attentional demands of the protocol tasks. Higher levels of prefrontal cortex activity were found to be related to a loss of gait automaticity in people with Parkinson's disease, but not in older adults. Behavioral clustering of navigated walking performance revealed high- and low-performing groups in people with Parkinson's disease and older adults, with corresponding differences in dorsolateral prefrontal cortex activity, aligning with models of compensatory neural activity.</p><p dir="ltr"><b>Conclusions</b>: Cognitive-motor ability during complex walking can be measured in a fea- sible and valid manner. Reduced gait automaticity is related to increased prefrontal cortex activity in people with Parkinson's disease, reflecting a specific compensatory mechanism. In older adults, prefrontal cortex activity is primarily related to age, reflect- ing a more general compensation. The compensatory mechanisms may begin to decline around the age of 70, leading to decreased complex walking performance.</p><h3 dir="ltr">List of scientific papers</h3><p dir="ltr">I. <b>Kvist, A.</b>, Bezuidenhout, L., Johansson, H., Albrecht, F., Ekman, U., Conradsson, D.M., Franzén, E., 2023. Using functional near-infrared spectroscopy to measure pre- frontal cortex activity during dual-task walking and navigated walking: A feasibility study. Brain and Behavior. <a href="https://doi.org/10.1002/brb3.2948">https://doi.org/10.1002/brb3.2948<br></a><br></p><p dir="ltr">II. <b>Kvist, A.</b>, Bezuidenhout, L., Johansson, H., Albrecht, F., Conradsson, D.M., Franzén, E., 2024. Validation of fNIRS measurement of executive demand during walking with and without dual-task in younger and older adults and people with Parkinson's disease. NeuroImage: Clinical. <a href="https://doi.org/10.1016/j.nicl.2024.103637">https://doi.org/10.1016/j.nicl.2024.103637<br></a><br></p><p dir="ltr">III. <b>Kvist, A.</b>, Peterson, D.S., Bezuidenhout, L., Johansson, H., Albrecht, F., Ekman, U., Conradsson, D.M., Franzén, E., 2026. Exploring gait automaticity and prefrontal brain activity during single and dual-task walking in aging and Parkinson's disease. Journal of NeuroEngineering and Rehabilitation. <a href="https://doi.org/10.1186/s12984-025-01864-w" rel="noreferrer" target="_blank">https://doi.org/10.1186/s12984-025-01864-w</a></p><p dir="ltr">IV. <b>Kvist, A.</b>, Bezuidenhout, L., Johansson, H., Ekman, U., Conradsson, D.M., Albrecht, F., Franzén, E., 2026. Drivers of navigated walking performance in aging and Parkinson's disease: insights from behavioral clustering, clinical and neuroimaging data. [Manuscript]</p>