Date of Award

August 2023

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Department

Psychology

First Advisor

Krista M Lisdahl

Committee Members

Christine Larson, Kristin Smith, Rodney Swain, Ann Swartz

Keywords

aerobic fitness, default mode network, functional connectivity, neurocognition, neurodevelopment, sex

Abstract

The beneficial effects of aerobic fitness on psychiatric and cognitive function in older adults have been well demonstrated in existing literature. However, less remains known about the relationship between aerobic fitness and neurocognitive health in emerging adults, who are less likely to suffer from underlying metabolic conditions. Further, few have examined potential sex differences. The transition from adolescence to young adulthood is associated with a reduction in physical activity and accumulating evidence suggests that poor aerobic fitness negatively impacts neurocognition. Therefore, it is crucial to better understand the relationship between aerobic fitness and neurocognitive health during adolescence and young adulthood when interventions may be pivotal. The current study aimed to better characterize the relationships between objectively measured aerobic fitness (VO2 max testing), resting-state functional connectivity in the default mode network (DMN), and neuropsychological performance in healthy emerging adults; sex differences were also examined. Results of the study showed that better aerobic fitness was associated with increased connectivity between the right PCC and left anterior cingulate. The VO2 max*sex interaction was significantly associated with increased connectivity between the right PCC and left precuneus (males displayed a more robust relationship) and increased connectivity between the left PCC and right middle temporal gyrus (females displayed a more robust relationship). Co-activation of the right PCC and left anterior cingulate associated with better aerobic fitness was negatively associated with verbal memory recall for the whole group. Further analysis separated by sex revealed males displayed a negative association between these regions and both verbal learning and memory, while females did not have a significant relationship. Co-activation of the left PCC and right middle temporal gyrus associated with better aerobic fitness was positively associated with verbal memory, with females showing a slightly greater benefit, though no significant sex differences were observed. Lastly, co-activation of the left PCC and right middle temporal gyrus was associated with better inhibition in males. Overall, results from this study contribute to a better understanding of the extent to which aerobic fitness impacts functional connectivity in the DMN of the developing brain and its relationship to neuropsychological performance in a sex-balanced, emerging adult sample. Findings may offer insights into the value of early preventive health behaviors aimed at improving neurocognitive health in youth prior to potential onset of psychiatric or neurologic disorders susceptible to disruptions in DMN connectivity.

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