Oculomotor and Cognitive Correlates of White Matter Organization in Military Personnel with Chronic Mild, Moderate, and Severe Traumatic Brain Injury.

INTRODUCTION: Traumatic Brain Injury (TBI) often involves diffuse axonal injury that is difficult to detect with clinical neuroimaging and may not be fully captured by standard cognitive tests. This study investigated the link between white matter microstructure, assessed by Diffusion Tensor Imaging (DTI), and performance on a multimodal neurocognitive eye tracking assessment. METHODS: Participants included n = 60 active duty military personnel, including n = 23 with chronic mild TBI (mTBI), n = 16 with chronic moderate-to-severe TBI (msTBI), and n = 21 TBI-negative controls. Cognitive and oculomotor functions were measured by the Fusion Multimodal Assessment, which records saccadic and manual responses under cognitive load, along with conventional neuropsychological tests and self-reported neurobehavioral symptoms and post-traumatic stress. White matter integrity was analyzed using regional Fractional Anisotropy (FA) and "pothole" analysis, which identifies clusters of abnormally low FA. RESULTS: Results demonstrated that oculomotor and cognitive performance from the Fusion Multimodal Assessment, including intra-individual variability of saccadic response speed, visual working memory performance, and difficulty ratings from this task, were associated with DTI FA and FA potholes in widespread white matter regions throughout the brain. In comparison, global performance on conventional cognitive measures showed limited/inconsistent associations with regional DTI FA or FA potholes, and severity of self-reported symptoms was associated with DTI FA potholes primarily in brainstem and sensorimotor pathways. DISCUSSION: These findings suggest that neurocognitive eye tracking may provide unique value for detecting impairments linked to white matter pathology in chronic TBI.