The Effects of Cardiovascular Health on Tasks of Executive Functions and Related Brain Activations in Healthy Older Adults

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2019-12

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Abstract

The combined effect of cardiovascular health factors (i.e., cardiovascular risk and physical fitness) on executive functions and its related brain activities in older adults has not yet been investigated. Moreover, the individual effects of these factors have also not been thoroughly investigated in normal aging. The current dissertation project was aimed to examine not only the separate but also the combined, effects of risk and fitness on executive functions and its related brain activities in older adults. The current project used three executive functions tasks of increasing difficulty: task-switching (switching between two tasks), working memory updating (switching and updating two streams of information), and working memory capacity (maintaining and coordinating 2-7 units of information). These tasks were separately studied using three experiments, with the first two being fMRI studies that measured brain activity in older adults during task-switching (Experiment 1) and working memory updating (Experiment 2). An independent sample of younger adults was also included in Experiments 1 and 2 as functional controls. The third experiment was a behavioral study that examined the effects of risk and fitness on working memory capacity in older adults. Results from the first two fMRI experiments showed that high cardiovascular risk and low physical fitness in older adults were separately associated with a) decreased suppressions of the Default Mode Network (DMN) regions, b) maladaptive overactivations in frontal regions, and c) reduced activations in tasksensitive regions. For risk factor, high cardiovascular risk, compared to low risk, in older adults was associated with reduced suppressions of bilateral lingual gyrus (task-switching, Experiment

  1. and posterior cingulate gyrus (working memory updating, Experiment 2), as well as reduced activations in a task-sensitive region (left precentral gyrus; Experiment 1). High risk older adults also showed maladaptive overactivations in right precentral gyrus in working memory updating (Experiment 2). For the fitness factor, low physical fitness, compared to high fitness, in older adults was associated with reduced suppression in DMN regions (right occipital pole: taskswitching, Experiment 1; frontal pole: working memory updating, Experiment 2), and maladaptive overactivations in frontal cortex (left IFG, Experiment 1). In addition to these separate effects of these two factors, combined effects of high risk and low fitness were observed in lingual gyrus and left IFG in task-switching (Experiment 1), and in right postcentral gyrus in working memory updating (Experiment 2). Such combined effects suggest that the abovementioned effects on brain activations increase with the increase in the number of cardiovascular health detrimental factors in older adults. Furthermore, age-related differences in brain regions associated with risk and fitness were evaluated against data from younger adults. Results showed that in task-switching (Experiment 1) age-related differences in activations were restricted to older adults with high risk or low fitness. In working memory updating (Experiment 2), however, age-related differences were observed not only in older adults with poorer cardiovascular health but also in those with better health. These results suggest that the mitigating effects of cardiovascular health on age-related differences in brain activations could be modulated by task difficulty. In the third experiment, cardiovascular risk and physical fitness, independently, were significant predictors of working memory capacity in older adults. The combined effect of risk and fitness was no more significant in predicting working memory capacity than risk effect alone. Post-hoc mediation analysis showed that the effect of physical fitness on working memory capacity was mediated by the cardiovascular risk, suggesting that cardiovascular risk was the most important cardiovascular health factor in predicting working memory capacity in older adults.

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Aging, Aging -- Physiological aspects, Brain -- Aging, Cardiovascular system -- Aging, Cardiovascular fitness, Health behavior -- Age factors

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©2020 Shuo Qin. All rights reserved.

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