The role of cortical morphometry of functional connectivity networks in understanding the associations between aerobic fitness and cognition

Abstract

A growing body of research has investigated the importance of lifestyle factors such as aerobic fitness and physical activity on cognitive and brain health across the human lifespan. Aerobic fitness levels in preadolescent children continue to decline despite previous evidence demonstrating the importance of aerobic fitness for physical health, as well as cognitive and brain health. On the opposite end of the age spectrum, aging coincides with reductions in cognitive ability along with cortical thinning, leading researchers to examine physical activity and aerobic fitness as modifiable lifestyle factors to better understand healthy aging. To this end, recent advances in the study of brain function has led to the understanding of functional connectivity networks, which are associated with cognitive abilities, aging, and development. The overarching goal of this dissertation was to utilize functional connectivity network architecture as an organizing principle to explore how cortical morphometry (surface area and cortical thickness) mediates the associations between aerobic fitness and cognition or scholastic performance during development and aging. This dissertation utilizes a sample of aging adults (60-80 years, N=226, study 1) and a sample of preadolescent children (7-9 years, N=167, study 2). Study 1 found that aerobic fitness and physical activity were associated with cognitive aging, and that relationship was mediated by cortical thickness (somatomotor, ventral attention, limbic, and default mode networks) and surface area (dorsal attention and frontoparietal networks) in specific functional connectivity networks that have been shown to exhibit greater amounts of cognitive aging. Because there were no significant mediations in study 2 with preadolescent children, the associations between aerobic fitness and cortical morphometry and the associations between cognitive/scholastic performance and cortical morphometry were investigated. Aerobic fitness was associated with surface area (somatomotor and default mode networks) and aspects of cognition (visual, somatomotor, dorsal and ventral attention, frontoparietal, limbic, and default mode networks) and scholastic performance (visual, somatomotor, dorsal and ventral attention, limbic, frontoparietal, and default mode networks) were associated with cortical morphometry. In conclusion, this dissertation investigated the importance of lifestyle factors, such as aerobic fitness and physical activity, with cortical morphometry in the context of functional connectivity networks. The examination of brain structure in the context of functional brain networks provides an important starting point for the ultimate integration of structural and functional brain health as a function of fitness/physical and cognition. Preadolescent children and aging adults undergo different trajectories with regards to brain and cognition. While thinning is predominantly associated with improved cognition in preadolescent children, the opposite is true for cognitive aging. As such, the results presented in this dissertation have important implications for public health for two vulnerable populations representing the opposite ends of the aging spectrum.--Author's abstract