Date of Award

Summer 2019

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

First Advisor

Porcelli, Anthony J.

Second Advisor

Gerdes, Alyson C.

Third Advisor

Nielson, Kristy A.

Abstract

Acute stress is unavoidable and may hinder basic reward processing underlying adaptive decision-making. Additionally, older adults may be at an increased risk of poor decision-making after exposure to acute stress due to age-related changes in cognitive and autonomic functioning. The current study assessed the influence of acute stress, autonomic reactivity, and age on a simple behavioral task during fMRI. Specifically, old and young adults completed a basic reward processing paradigm (i.e., where participants received monetary rewards and punishments) after exposure to acute stress (i.e., social evaluative cold pressor) or control procedure between-subjects. In the young group, differential responses for monetary rewards over punishments were observed in executive functioning regions (i.e., dlPFC and dACC), whereas older participants displayed reward-related differential activity in ventral-midline structures commonly associated with emotion processing (e.g., mPFC and ventromedial ACC). Exposure to acute stress significantly reduced differential engagement of the dmPFC and left putamen, an effect driven largely by older adults. Additionally, parasympathetic reactivity (measured via HRV) expressed during acute stress exposure predicted differential activity within these regions; in mPFC, this effect was significantly moderated by age. These findings highlight anatomically distinct patterns of activation underlying reward processing in older versus younger adults and offers preliminary support for the proposal that the aged may be at increased risk for stress-related changes in neural processing of rewards and punishments. Furthermore, parasympathetic reactivity during acute stress may be a viable biomarker for predicting stress-related alterations in fronto-striatal reward processing (particularly in older adults).

Available for download on Friday, July 24, 2020

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