This dissertation investigated the association of physical activity with cognition in two cross-sectional studies. Physical activity has been positively associated with cognitive function, and in older adult populations has shown an additional benefit for carriers of the ApoE- å4 allele. Cognitive training has also revealed a benefit for improved cognitive performance. Questions remain, however, about the interaction of these factors in their relation with cognition. One study addressed the relationship between physical activity and cognitive performance during executive function and working memory challenges in adults ages 50-70, and the other explored the role that physical activity plays in learning in adults ages 22-50 undergoing an online cognitive training intervention. In both studies, regard for influence of the ApoE genotype was considered, and the concept of specificity of physical activity was explored through employment of measures of both cardiovascular fitness and weekly physical activity kilocalorie expenditure.

The study of older adults revealed that performance on a working-memory task was positively related to weekly kilocalorie expenditure in APOE-å4 carriers, with no such benefit for non-carriers during a moderate challenge condition of the task, while a positive relationship was revealed for both å4 carriers and non-carriers during a more challenging condition, but the magnitude of the relationship was greater in å4 carriers. The study of younger adults revealed no transfer benefits for cognitive training; however, cardiovascular fitness was positively related to performance after the intervention on a transfer task of proactive interference, and a positive trend was also found for cardiovascular fitness on a divided-attention language vocabulary learning task. No association was observed with regard to APOE-å4 genotype for any post-intervention task or learning transfer challenge. Taken together, these studies reveal that physical activity is associated with improved cognition in younger and older adults alike, but with specificity as to volume or intensity of physical activity mediating the relationship, cognitive processes benefited, and the role that the APOE-å4 genotype plays.