Date of Degree

9-2021

Document Type

Thesis

Degree Name

M.S.

Program

Cognitive Neuroscience

Advisor

Junghoon J. Kim

Subject Categories

Cognitive Neuroscience | Medical Anatomy | Nervous System | Neurology | Neurosciences | Trauma

Keywords

Apathy, Traumatic Brain Injury, MRI, Brain Morphometry, Anterior Cingulate Gyrus, Nucleus Accumbens

Abstract

Apathy, defined as disinterest and loss of motivation, is a common complication after moderate-severe traumatic brain injury (msTBI). The existing body of research in various neurological and neurodegenerative disorders suggests that apathetic symptoms may be associated with variation in the volume of the brain regions such as dorsal anterior cingulate cortex and ventral striatum. However, the longitudinal pattern of TBI-induced atrophy in these key regions and its relationship with apathy symptoms remain to be demonstrated. The current study aimed to describe the atrophy pattern in the anterior cingulate gyrus (ACG) and the nucleus accumbens (NAc; part of ventral striatum) after msTBI and examine the brain-behavior relationship between the degree of atrophy in these regions and apathetic symptoms during the first year after msTBI. To this end, 30 patients with msTBI were assessed at 3, 6, and 12 months post-injury for neuroimaging and behavioral evaluations. Thirty-five matched healthy volunteers were evaluated once as a control group. At all time points, a significant group difference was found between patients and controls in terms of apathy measured by the apathy subscale of the Frontal Systems Behavior Scale, indicating that apathetic symptoms after msTBI persist throughout the first year post-injury. Similarly, the group difference in cortical thickness of ACG was significant at all three time points. In contrast, the group difference in NAc volume was significant only at 12 months post-injury, suggesting a delayed onset of progressive neurodegeneration in NAc. Cortical thickness in ACG, but not NAc volume, showed an expected inverse relationship with apathy scores at all time points—that is, larger degree of atrophy associated with higher apathy score (Spearman’s rho ranging from -.26 to -.39). However, the statistical significance of this relationship did not survive multiple comparison correction. A potentially critical role of ACG in post-traumatic apathy in msTBI is discussed.

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