The effects of physical activity on the brain and cognition during childhood

This dissertation investigates the influence of physical activity on the cognitive and brain health of children. It is motivated by experimental studies in rodents and older adults that demonstrate a positive influence of physical activity and aerobic exercise on cognition, brain structure, and brain function. Furthermore, a growing number of cross-sectional studies suggest that physical activity and higher levels of aerobic fitness in children are positively associated with brain structure, brain function, cognition, and school achievement. Higher fit children have larger brain volumes in the basal ganglia and hippocampus, which relate to superior performance on tasks of cognitive control and memory, respectively, when compared to their lower fit peers. Higher fit children also show superior brain function during tasks of cognitive control and better academic achievement compared to lower fit and less active children.;This dissertation extends previous cross-sectional research by examining the influence of a 9-month randomized controlled after school physical activity program on brain structure, brain function, and cognition in children. Children were randomized into a physical activity intervention group or a wait list control group, and VO2 max fitness testing, magnetic resonance imaging (MRI) and cognitive testing were conducted before and after the 9-month intervention. Structural brain measures included volumes of the basal ganglia and hippocampus characterized by FMRIB's Integrated Registration and Segmentation Tool (FIRST) as well as the integrity of white matter tracts using diffusion tensor imaging (DTI). Brain function was assessed using functional magnetic resonance imaging (fMRI) while children performed a task that required attentional, interference and inhibitory control.;Although this dissertation is limited by a small sample size and lack of statistical interactions, it is one of the first studies to use MRI techniques to make preliminary conclusions about the association between participation in an after school physical activity program and cognitive and brain health in children. Eight- to 9-year-old children who participated in more than the recommended 60 minutes of moderate to vigorous physical activity, 5 days per week, for approximately 9 months, showed within-group increases in the volume of the dorsal striatum of the basal ganglia and the hippocampus. Physically active children also demonstrated within-group increases in fractional anisotropy (an estimation of white matter integrity) and decreased radial diffusivity (an estimation of myelination) in a global network of white matter tracts throughout the brain from pre-test to post-test. Additionally, children in the physical activity program demonstrated within-group improvements in attentional control during a flanker task, which paralleled decreases in fMRI brain activation in the right anterior prefrontal cortex. In fact, their changes in activation and performance led to brain function similar to young adults. Children in the wait list control group did not show changes in anterior prefrontal activation or performance from pre-test to post-test.;Given that children have become increasingly sedentary, unfit and overweight, understanding the benefits of physical activity on cognition is of great significance. This dissertation suggests that physical activity may improve the cognitive and brain health of 8- to 9-year-old children. Although the results are preliminary, they have implications for the biological potential of the brain during periods of maturation and brain development, and suggest that the developing brain is plastic and sensitive to lifestyle factors. In particular, this dissertation demonstrates that physical activity during childhood may influence the volume of the basal ganglia and hippocampus, the integrity of white matter tracts, and brain activation in the prefrontal cortex. Hopefully, the results will raise public awareness of the cognitive benefits of physical activity during childhood.