Hello and welcome to The Mobility Brief. It’s Monday, August 11th, 2025. This is the weekly podcast from The Gray Centre for Mobility and Activity at St. Joseph's Health Care London. This week, we are sharing five updates from the centre.

First up, a recent study addresses the question: Does brain volume explain why walking while distracted is linked to dementia risk? This research, with contributions from Dr. Manuel Montero-Odasso, examined the connection between what is called dual-task gait cost—the change in walking performance while doing a simultaneous mental task—and the subsequent onset of dementia. Using models, the researchers investigated if the volume of grey matter in the brain acts as a mediating factor in this association. The study was founded on the idea that the cost of dual-task walking is not just a consequence of structural brain changes, but could be a dynamic expression of the brain's vulnerability. The work explored the possibility that gait impairment and subtle structural alterations in the brain co-evolve, and that performance on a dual-task test could capture early functional disturbances before a clinical diagnosis. The authors clarified their primary objective was not to assert a strict one-way causal pathway, but to see if structural brain changes could mediate the predictive link between dual-task gait cost and dementia risk.

Next, we turn to a question about recovery. After a stroke, is the brain's effort to keep balance linked to fatigue? Research from Jamie Fleet, Ricardo Viana, Robert Teasell, and Sue Peters explored this connection. They measured brain activation in the prefrontal cortex of patients with hemiparesis while they performed standing balance tasks of varying difficulty. Using functional near-infrared spectroscopy, the team found that more challenging postures resulted in greater brain activation. They also noted that participants who reported higher levels of fatigue showed more activation on the side of the brain where the stroke had occurred, compared to the other side.

Our final update this week poses a question that at first seems counterintuitive: Could brain damage in a key motor region be linked to better movement in Parkinson's? Research with contributions from Dr. Manuel Montero-Odasso investigated the association between motor severity and white matter hyperintensities, which are areas of damage visible on brain scans. In a cross-sectional study of 140 participants with Parkinson's disease, the team measured the volume of these lesions in various brain regions, including the basal ganglia and thalamus. The analysis showed that a greater amount of damage in the basal ganglia and thalamus was associated with better motor function. Lesions in cortical brain regions did not show a similar link. The authors suggest that disruption of inhibitory circuitry in the basal ganglia by these lesions might recalibrate motor output.

Another update from the centre looks at how a combination of health risks affects the brain across different neurodegenerative diseases. This research, with contributions from Dr. Manuel Montero-Odasso, examined over 500 participants from the Ontario Neurodegenerative Disease Research Initiative. The study included individuals with one of five conditions—mild cognitive impairment or Alzheimer’s disease, frontotemporal dementia, cerebrovascular disease, Parkinson’s disease, or ALS—alongside a group of healthy controls. Each person was assigned a vascular risk score based on five factors: hypertension, diabetes, dyslipidemia, obesity, and smoking history. The team then used MRI scans to evaluate the integrity of the brain's white matter. The analysis showed that vascular risk factors were more prevalent in the disease cohorts compared to the controls. A higher risk score was associated with a greater likelihood of having mild cognitive impairment, frontotemporal dementia, or cerebrovascular disease. Across the entire sample, a high risk score was also linked to reduced white matter integrity.

Another piece of work from the centre asks whether peer support and a wearable device can help people with a lower limb amputation move more. Research involving Michael Payne and Dalton Wolfe is testing an intervention that combines weekly virtual peer coaching, web-based modules, and a wearable activity monitor for an eight-week period. In this pilot randomized controlled trial, participants in the intervention group get access to this program, while a control group continues with usual care. The aim is to assess the feasibility of this approach for a future, larger study. The primary outcomes to be measured are daily physical activity counts from an activity monitor and self-efficacy for exercise. The results are intended to inform the design of a definitive trial to determine the effectiveness of the peer-led program.

So, from the connection between walking while distracted and dementia risk, to the finding that specific brain lesions could be associated with better motor function in Parkinson's, the research we shared today examines the links between how we move and the state of our brains. These studies look at factors from vascular health to peer support, all in relation to physical and cognitive outcomes. Thank you for listening to The Mobility Brief. Join us again next week.