Date of Graduation

12-2022

Document Type

Thesis

Degree Name

Bachelor of Arts

Degree Level

Undergraduate

Department

Biological Sciences

Advisor/Mentor

Leong, Josiah

Committee Member/Reader

Beaulieu, Jeremy

Committee Member/Second Reader

Walker, Kate

Committee Member/Third Reader

Dowdle, Andrew

Abstract

The prominence of anxiety disorders in today’s general population is a major public health concern. Advancing research of the underlying pathophysiology of anxiety disorders can lead to the discovery of effective treatment interventions to treat the mental and physical symptoms of anxiety, and thus improve quality of life. This study aimed to examine two brain areas in the limbic and reward systems, the amygdala and Nucleus Accumbens (NAcc), and the structural white matter connection between them. This neural circuit assigns affective valence to environmental stimuli and motivates behavior to avoid potential harm. This study utilized diffusion Magnetic Resonance Imaging (dMRI) from the longitudinal multi-site Adolescent Brain Cognitive Development (ABCD) study to investigate the structure of these brain regions and the coherence of the white matter tract that directly connects them. Results indicated that in adolescents with clinical anxiety, significantly reduced Fractional Anisotropy (FA; an index of decreased neuron density, neuronal disorganization, and demyelination) and significantly reduced volume are observed in the BasoLateral nucleus of the Amygdala (BLA) in both the left and right hemispheres when compared to controls. This diffusion metric of FA was also found to be significantly correlated with volume in the BLA of both hemispheres. Additionally, in the BLA-NAcc tract of the left hemisphere, FA was significantly reduced in the first 25 nodes nearest the BLA for anxious participants compared to controls. Reduced FA within the BLA was also found to be significantly correlated with increased anxiety symptom severity. This study investigated structural differences between anxious and non-anxious adolescents during a period of maturation in which individuals are at an elevated risk of developing an anxiety disorder. The ABCD study is ongoing and provides the opportunity for future research to build from this presented study and investigate how anxiety may induce cognitive changes over time.

Keywords

anxiety, adolescence, nucleus accumbens, amygdala, Adolescent Brain Cognitive Development study, fractional anisotropy

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