Verbal Retrieval Deficits Due to Traumatic Brain Injury Are Linked to White Matter Changes Mediated by Altered Oscillatory Brain Activity
Hsueh-Sheng Chiang1, Jeremy Strain2, Ashna Adhikari3, Jeffrey Spence3, Kyle Womack2, Munro Cullum4, John Hart3
1Beth Israel Deaconess Medical Center, 2Washington University in St. Louis, 3The University of Texas at Dallas, 4University of Texas Southwestern Medical Center
Objective:
This study investigated associations between verbal retrieval (VR) deficits and changes in electrophysiological activity and white matter structure in veterans with chronic traumatic brain injury (TBI).
Background:
VR deficits are a common sequela of TBI with unclear neural mechanisms and limited treatment options.
Design/Methods:
Sixty veterans (42 ± 10.6 years, 4 women) with TBI histories (>1 year) underwent neuropsychological testing and an EEG-based Go-NoGo task. Regional skeletonized white matter tract fractional anisotropy (FA) was quantified using diffusion-weighted imaging obtained in 41 subjects. Participants were categorized into those with impaired VR (VR-, n =27; 20 with FA; < -1.5 Z in letter/category fluency, picture naming, or total verbal learning) versus intact VR (VR+, n = 33; 21 with FA). We analyzed group differences in (1) frontal theta/alpha activity during Go/NoGo trials, (2) relationships between theta/alpha activity and executive function [EF]/processing speed [PS], and (3) correlations between FA in specific tracts and theta/alpha activity, using General Linear Modeling adjusting for age and education. We examined direct and indirect (via theta/alpha) effects of FA on cognition using mediation analyses.
Results:
The VR- group exhibited significantly lower frontal NoGo theta power (p = 0.015). Higher Go/NoGo frontal theta power predicted better PS in the VR- but not VR+ group (p = 0.002). In the VR- compared to VR+ group, greater frontal Go theta power correlated with higher FA values in the right superior longitudinal fasciculus (SLF), left perforant pathway (PP), bilateral frontal occipital fasciculi (FOF), and forceps minor (FMin) (ps = 0.006 – 0.049). The right SLF, bilateral FOFs, and FMin showed significant indirect effects on PS via frontal theta activity.
Conclusions:
VR deficits may be influenced by structural changes in specific white matter tracts following TBI, mediated by altered frontal theta activity. These findings offer biological insights for designing novel assessment and intervention strategies for TBI.
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