Date of Award

5-2025

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

College/School

College of Humanities and Social Sciences

Department/Program

Psychology

Thesis Sponsor/Dissertation Chair/Project Chair

Joshua Sandry

Committee Member

Erin Kang

Committee Member

Michael Bixter

Committee Member

Ekaterina Dobryakova

Abstract

Traumatic brain injury (TBI) occurs following injury to head, resulting in disruption of normal brain functioning. During the chronic stages (greater than one year postinjury), those with TBI may experience ongoing symptoms. Executive dysfunction, including inhibition, is often seen. Neuropsychological measures of inhibition applied in basic research utilize response time across several trials, where participants complete trials with and without inhibitory control. Refined measurement approaches include trial-by-trial performance to capture response time inconsistencies or variability within the subject, known as intraindividual variability. Typical methods of measuring intraindividual variability violate statistical assumptions given that response time distributions are positively skewed. One alternative method includes applying an ex-Gaussian distribution analysis to the response time curve that decomposes and provides information regarding the shape of the response time distribution, allowing for a more nuanced understanding of response time patterns. The current investigation aimed to understand the mechanisms that underlie inhibition in chronic moderate-severe TBI compared to healthy controls utilizing ex-Gaussian parameter estimates. Additionally, the study aimed to identify structural neural correlates of these parameter estimates. Results indicate more overall slowing and more extremely slow responses in incongruent trials compared to congruent trials. Ex-Gaussian parameter estimates were not significantly different between chronic moderate-severe TBI and healthy controls, suggesting impairments may improve over time. Overall slowing was associated with several areas in the frontal regions of the brain that are often related to inhibitory control in chronic moderate-severe TBI. Findings provide considerations into utilizing math modeling in analyzing inhibition within chronic moderate-severe TBI.

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