Date of Award

Spring 2026

Document Type

Open Access Thesis

Department

Exercise Science

First Advisor

Jill Stewart

Abstract

This study investigates the effect of age on three major dopaminergic reward pathways using resting state functional magnetic resonance imaging. Resting state imaging refers to low-frequency brain connectivity in the absence of task demands or directed thought patterns. The pathways included in this thesis are as follows: the nigrostriatal, mesolimbic, and mesocortical pathways. These pathways rely on dopamine and are known for a variety of functions, most notably regulating responses to rewarding and aversive stimuli. This analysis compared the connectivity between key regions of interest, where transmission originates in the midbrain and substantia nigra, and terminates in the orbitofrontal cortex, the ventral striatum, nucleus accumbens, and primary motor cortex. Participants in this analysis were between the ages of 20 and 80 years old and divided into three age groups. The connectivity of select brain region pairs were represented independently by Fisher’s Z transformation scores and assessed for statistical significance with one-way analysis of variance testing. To understand how much influence age had on brain connectivity strength a linear regression was conducted for all network pairs. Socioemotional scores from the National Institute of Health Toolbox – Emotion Battery (negative affect, psychological well-being, and social satisfaction) were compared between age groups. The relationship between brain connectivity and socioemotional scores was investigated with exploratory Pearson’s correlations because the relationship between reward connectivity and socioemotional scores is not well understood. The results of this study identified significant differences between groups and aging for socioemotional  scores for negative affect and social satisfaction but not psychological well-being. There were significant differences in resting state connectivity in some of the resting state network ROI pairs. In the left hemisphere, the midbrain to orbitofrontal cortex, midbrain to primary motor cortex, and SN to putamen connections were significantly different between young and old groups only. In the right hemisphere, the midbrain to orbitofrontal cortex connectivity was statistically significant between young and old groups. The regression analysis yielded similar results, however the reported effect size of these analyses were small. Finally, the correlation analysis found significant but weak correlations for select networks and socioemotional scores. The results of this study will assist in deepening our understanding of the relationship between dopamine function and brain connectivity across the lifespan.

Rights

© 2026, Julia Cardarelli

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