This thesis first explored the effects of concurrent spatial attention and working memory task performance on over-ground gait in healthy young and older adults. It then compared over-ground gait parameters and working memory performance in mild Alzheimer’s Disease (AD) and normal controls (NC) and investigated costs of dual-tasking on working memory performance and cadence during treadmill walking at preferred walking speed in the two groups. Furthermore, it explored these differences in AD and NC groups in relation to their subcortical hyperintensities (SH) that were rated using standardized scales on MRI. Reaction times and accuracy on working memory performance measures were collected under single and dual task conditions. Over-ground gait parameters were measured on an automated walkway. Costs of dual-tasking on gait parameters and working memory performance were measured at a constant velocity on a treadmill. The hypotheses that working memory influences gait performance and that a higher SH burden negatively influences over-ground gait and costs of dual-task conditions, were supported in a series of experiments. Gait slowed down while performing working memory and spatial attention tasks in young and older adults. Patients with mild AD, compared to NC, had a slower gait velocity, shorter stride length and lower cadence on the walkway. When the two groups were subdivided into higher and lower SH groups based on their median SH score, the NC group with lower SH burden walked significantly faster with a higher cadence and a longer stride length than the other three groups. Lastly, a higher SH burden negatively influenced working memory performance in NC while in mild AD patients, it had negative influences on adaptive changes in gait while dual-tasking. These results suggest that, in dual-task condition, SH interfere with processing speed in NC and on gait in AD. These findings provide new insights in to tradeoffs during dual tasking in relation to cerebrovascular disease. This has ecological implications because of the prevalence of small vessel disease in aging and dementia, may impact on predicting falls in AD.

This thesis first explored the effects of concurrent spatial attention and working memory task performance on over-ground gait in healthy young and older adults. It then compared over-ground gait parameters and working memory performance in mild Alzheimer’s Disease (AD) and normal controls (NC) and investigated costs of dual-tasking on working memory performance and cadence during treadmill walking at preferred walking speed in the two groups. Furthermore, it explored these differences in AD and NC groups in relation to their subcortical hyperintensities (SH) that were rated using standardized scales on MRI. Reaction times and accuracy on working memory performance measures were collected under single and dual task conditions. Over-ground gait parameters were measured on an automated walkway. Costs of dual-tasking on gait parameters and working memory performance were measured at a constant velocity on a treadmill. The hypotheses that working memory influences gait performance and that a higher SH burden negatively influences over-ground gait and costs of dual-task conditions, were supported in a series of experiments. Gait slowed down while performing working memory and spatial attention tasks in young and older adults. Patients with mild AD, compared to NC, had a slower gait velocity, shorter stride length and lower cadence on the walkway. When the two groups were subdivided into higher and lower SH groups based on their median SH score, the NC group with lower SH burden walked significantly faster with a higher cadence and a longer stride length than the other three groups. Lastly, a higher SH burden negatively influenced working memory performance in NC while in mild AD patients, it had negative influences on adaptive changes in gait while dual-tasking. These results suggest that, in dual-task condition, SH interfere with processing speed in NC and on gait in AD. These findings provide new insights in to tradeoffs during dual tasking in relation to cerebrovascular disease. This has ecological implications because of the prevalence of small vessel disease in aging and dementia, may impact on predicting falls in AD.

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