Sex-Differences in the Early Detection of Dementia Risk Using a Cognitive-motor Integration Task

Cognitive-motor integration (CMI) involves concurrent thought and action which requires the interaction of large brain networks. Our research objectives were to examine the effect that dementia risk has on the ability to integrate rules into action and to investigate sex-related differences in this rule-based motor performance. Given that early-stage dementia involves neural network dysfunction, problems with CMI may prove useful for early dementia detection. Males and females at high- and low-dementia risk were tested on increasingly spatially-dissociated visuomotor tasks. We observed significantly greater endpoint error scores and corrective path lengths in females compared to males in the most complex CMI condition. These data suggest that underlying brain networks controlling simultaneous thought and action differ between the sexes, and that dementia risk may affect female CMI performance to a greater extent. Thus, sex-related differences must be taken into account when assessing CMI performance as a means to examine dementia risk-related functional abilities

Neural Correlates of Unimanual and Bimanual Eye-Hand Coordination across Healthy and Dementia-Risk Populations

Eye-hand coordination is essential to our functional independence and relies on communication between widespread brain regions for successful unimanual and bimanual motor control. Eye-hand coordination performance has been shown to differ between the sexes, as well as between healthy aging individuals and those with dementia risk. The studies included within this dissertation were designed to characterize the structural and functional neural correlates of skilled movements across various populations in order to gain a better understanding of previously reported behavioural performance differences. The first two studies investigated changes in structural and functional integrity, respectively, of brain networks that may underlie known visuomotor behavioural deficits in older adults with an increased genetic (APOE e4) risk for Alzheimer’s disease. Alzheimer’s disease is thought to be a disconnection syndrome with characteristic patterns of disruption to structural and functional connectivity in the brain. A visuomotor task requiring the integration of different cognitive and motor domains via communication across multiple brain regions presents one way to test the integrity of these brain networks. The anatomical, diffusion-weighted, and resting state functional connectivity imaging data revealed that in older adult APOE e4 carriers, visuomotor deficits were predicted by i) lower grey matter volume and thickness of medial temporal lobe regions, ii) lower white matter integrity in several major tracts, and iii) decreased functional connectivity within the default mode and dorsal attention networks, in advance of any cognitive deficits. Historically, sex differences in unimanual and bimanual eye-hand coordination have also been observed, and a better understanding of the neural correlates of these differences could inform clinical practices on how to better tailor bimanual movement-based rehabilitation to the individual. The third study investigated the sex differences in functional connectivity of bimanual control, demonstrating connectivity differences between men and women despite equivalent behavioural performance. Taken together, these data provide novel insight into the neural correlates underlying one of our most fundamental human behaviours, eye-hand coordination, and their potential clinical implications

Neural Correlates of Unimanual and Bimanual Eye-Hand Coordination across Healthy and Dementia-Risk Populations

Eye-hand coordination is essential to our functional independence and relies on communication between widespread brain regions for successful unimanual and bimanual motor control. Eye-hand coordination performance has been shown to differ between the sexes, as well as between healthy aging individuals and those with dementia risk. The studies included within this dissertation were designed to characterize the structural and functional neural correlates of skilled movements across various populations in order to gain a better understanding of previously reported behavioural performance differences. The first two studies investigated changes in structural and functional integrity, respectively, of brain networks that may underlie known visuomotor behavioural deficits in older adults with an increased genetic (APOE e4) risk for Alzheimers disease. Alzheimers disease is thought to be a disconnection syndrome with characteristic patterns of disruption to structural and functional connectivity in the brain. A visuomotor task requiring the integration of different cognitive and motor domains via communication across multiple brain regions presents one way to test the integrity of these brain networks. The anatomical, diffusion-weighted, and resting state functional connectivity imaging data revealed that in older adult APOE e4 carriers, visuomotor deficits were predicted by i) lower grey matter volume and thickness of medial temporal lobe regions, ii) lower white matter integrity in several major tracts, and iii) decreased functional connectivity within the default mode and dorsal attention networks, in advance of any cognitive deficits. Historically, sex differences in unimanual and bimanual eye-hand coordination have also been observed, and a better understanding of the neural correlates of these differences could inform clinical practices on how to better tailor bimanual movement-based rehabilitation to the individual. The third study investigated the sex differences in functional connectivity of bimanual control, demonstrating connectivity differences between men and women despite equivalent behavioural performance. Taken together, these data provide novel insight into the neural correlates underlying one of our most fundamental human behaviours, eye-hand coordination, and their potential clinical implications

Thinking-While-Moving Exercises May Improve Cognition in Elderly with Mild Cognitive Deficits: A Proof-of-Principle Study

Background: Noninvasive interventions to aid healthy cognitive aging are considered an important healthcare priority. Traditional approaches typically focus on cognitive training or aerobic exercise training. In the current study, we investigate the effect of exercises that directly combine cognitive and motor functions on visuomotor skills and general cognition in elderly with various degrees of cognitive deficits. Subjects and Methods: A total of 37 elderly, divided into four groups based on their level of cognition, completed a 16-week cognitive-motor training program. The weekly training sessions consisted of playing a videogame requiring goal-directed hand movements on a computer tablet for 30 minutes. Before and after the training program, all participants completed a test battery to establish their level of cognition and visuomotor skills. Results: We observed an overall change in visuomotor behavior in all groups, as participants completed the tasks faster but less accurately. More importantly, we observed a significant improvement in measures of overall cognition in the subaverage cognition group and the mild-to-moderate cognitive deficits group. Conclusion: Our findings indicate that (1) cognitive-motor exercises induce improved test scores, which is most prominent in elderly with only mild cognitive deficits, and (2) cognitive-motor exercises induce altered visuomotor behavior and slight improvements in measures of general cognition