Graduate Studies

 

First Advisor

Kathy Chiou

Degree Name

Doctor of Philosophy (Ph.D.)

Department

Psychology

Date of this Version

6-2024

Document Type

Dissertation

Citation

A dissertation presented to the faculty of the Graduate College of the University of Nebraska in partial fulfillment of requirements for the degree of Doctor of Philosophy

Major: Psychology

Under the supervision of Professor Kathy Chiou

Lincoln, Nebraska, June 2024

Comments

Copyright 2024, Jeremy A. Feiger. Used by permission

Abstract

Traumatic brain injury (TBI) survivors experience a range of sequelae including neurobiological brain changes, cognitive impairment, psychological difficulties, and functional changes. Neuropsychological assessment after injury is used to characterize current strengths and weaknesses to inform prognosis and interventions. There is currently no reliable and consistent method of assessing and classifying injuries in the post-acute and chronic phases of moderate to severe TBI (msTBI) that is associated with long term psychosocial outcomes. This study aimed to combine the use of within-person variability on neuropsychological test batteries and in cognitive response latency, known as intra-individual variability (IIV), with a novel cognitive phenotyping method to investigate the clinical and classification utility of neuropsychological IIV in msTBI survivors.

Adult msTBI survivors (n = 31) and healthy control participants (n = 30) completed a comprehensive neuropsychological testing battery, a computerized dual working memory flanker task, and assessments of mood, behaviors, and functional impairment. When compared to healthy controls, msTBI survivors demonstrated higher IIV on the overall test battery, learning and memory, executive functioning, and attention/working memory domains. Overall test battery IIV was not associated with any of the outcome domains measured. TBI survivors had significantly higher reaction time IIV compared to healthy controls especially at a high working memory demand level, however; there were no significant differences between working memory demand levels for either group. Cluster analysis results identified four distinct IIV based cognitive phenotypes which differed on quality-of-life ratings, impairment in ability functioning, and participation in social roles and activities. Finally, results of goodness of fit tests were mixed and a within domain IIV model was the best fit for only quality of life ratings and impairment in adjusting to limitations after brain injury.

Despite noted limitations, the current findings have implications for advancing the precision and utility of clinical neuropsychological assessment with msTBI. Further research is needed to better understand connections between IIV and clinical outcomes, use of IIV as a discrete construct in clinical assessment, and neurocognitive mechanisms driving IIV changes following TBI.

Advisor: Kathy Chiou

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