A Preliminary High-Definition Fiber Tracking Study of the Executive Control Network in Blast-Induced Traumatic Brain Injury

Abstract

Blast-induced traumatic brain injury (bTBI) is common in veterans of the Iraq- and Afghanistan-era conflicts. However, the typical subtlety of neural alterations and absence of definitive biomarkers impede clinical detection on conventional imaging. This preliminary study examined the structure and functional correlates of executive control network (ECN) white matter in veterans to investigate the clinical utility of using high-definition fiber tracking (HDFT) to detect chronic bTBI. Demographically similar male veterans (N = 38) with and without bTBI (ages 24 to 50 years) completed standardized neuropsychological testing and magnetic resonance imaging. Quantitative HDFT metrics of subcortical-dorsolateral prefrontal cortex (DLPFC) tracts were derived. Moderate-to-large group effects were observed on HDFT metrics. Relative to comparisons, bTBI demonstrated elevated quantitative anisotropy (QA) and reduced right hemisphere volume of all examined tracts, and reduced fiber count and increased generalized fractional anisotropy in the right DLPFC-putamen tract and DLPFC-thalamus, respectively. The Group × Age interaction effect on DLPFC-caudate tract volume was large; age negatively related to volume in the bTBI group, but not comparison group. Groups performed similarly on the response inhibition measure. Performance (reaction time and commission errors) robustly correlated with HDFT tract metrics (QA and tract volume) in the comparison group, but not bTBI group. Results support anomalous density and integrity of ECN connectivity, particularly of the right DLPFC-putamen pathway, in bTBI. Results also support exacerbated aging in veterans with bTBI. Similar ECN function despite anomalous microstructure could reflect functional compensation in bTBI, although alternate interpretations are explored.

Differential Change in Oculomotor Performance among Female Collegiate Soccer Players versus Non-Contact Athletes from Pre- to Post-Season

“…[65][66][67][68][69][70][71][72] Recent evidence suggests head trauma may disrupt proper functioning of cortico-striatal projections, which supports the suggestion that this mechanism may underlie the group effects observed on anti-saccade error rate. 73,74 Our hypothesis that CONT groups would demonstrate differential change on MGS spatial accuracy, a measure of spatial working memory ability, relative to NON-CONT from pre-to post-season, was not supported. Given that differential change was observed among groups with varying levels of estimated exposure to head impacts on anti-saccade error rate but not on MGS spatial accuracy, it is possible that inhibitory control abilities may be more susceptible to the effects of head impact exposure relative to spatial working memory.…”

Anhedonia following mild traumatic brain injury in rats: A behavioral economic analysis of positive and negative reinforcement

“…[58][59][60][61][62] TBI modifies neural circuits involving both DLPFC and dopamine systems. [63][64][65][66] While dopaminergic systems have largely been implicated in both positive and negative reinforcement, any mechanistic explanation of our results will have to include differential actions of TBI on avoidance of foot shock, but not escape or positive reinforcement. 67,68 Our results showing a lack of effect of mTBI on positive reinforcement are consistent with one study, but at odds with others.…”

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