Abstract

Cognitive performance declines in depression and increases with physical activity. These changes may in part be due to changes in the level of neurogenesis (the generation and survival of adult-born neurons), which decreases with depression and increases with physical activity. Pattern separation (the formation of distinct neural representations of incoming information through orthogonalizing similar patterns of activation) has also been linked to neurogenesis. This project explores pattern separation within these two populations through three experiments.Experiment 1. Previous research has found impaired pattern separation among individuals with higher depression scores, but who have not been diagnosed with Major Depressive Disorder (MDD). This experiment sought to expand these findings and evaluated behavioral differences during the performance of a continuous recognition pattern separation task among women with MDD and age- and education-matched controls. It was hypothesized that clinically depressed participants would have lower pattern separation scores and would be more likely to incorrectly identify lure stimuli as "old". Contrary to this prediction, clinically depressed participants had higher pattern separation scores, while controls were more likely to misidentify lure items as "old".Experiment 2. While there are many known benefits of regular physical activity, the majority of individuals in the United States do not engage in the recommended levels of fitness training. Furthermore, there have only been a limited number of studies evaluating the effect physical activity may have on cognitive abilities and neurological components and none have evaluated what effect the recommended levels of fitness may have on these areas. The second experiment evaluated differences between individuals with varying levels of physical activity using functional magnetic resonance imaging (fMRI) during the performance of a continuous recognition pattern separation task. It was hypothesized that participants with self-reported higher levels of physical activity would have greater activation in the CA3/dentate gyrus subregions of the hippocampus than those with lower fitness levels and sedentary individuals. Surprisingly, there were no activation differences across groups. Experiment 3. The final experiment explored diffusion tensor imaging (DTI) differences in physical activity levels with the same sample used in Experiment 2. It was hypothesized that participants with self-reported higher levels of physical activity would have indications of increased white matter integrity compared to those with lower fitness levels and sedentary individuals. There were significant differences across groups in DTI measures of white matter integrity (axial diffusivity or AD) in bilateral cingulum, the left temporal middle gyrus, and the right uncinate fasciculus.

Degree

PhD

College and Department

Family, Home, and Social Sciences; Psychology

Rights

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