Objectives: Blast explosions are the most frequent mechanism of traumatic brain injury (TBI) in recent wars, but little is known about their long-term effects. Methods: Functional connectivity (FC) was measured in 17 veterans an average of 5.46 years after their most serious blast related TBI, and in 15 demographically similar veterans without TBI or blast exposure. Subcortical FC was measured in bilateral caudate, putamen, and globus pallidus. The default mode and fronto-parietal networks were also investigated. Results: In subcortical regions, between-groups t tests revealed altered FC from the right putamen and right globus pallidus. However, following analysis of covariance (ANCOVA) with age, depression (Center for Epidemiologic Studies Depression Scale), and posttraumatic stress disorder symptom (PTSD Checklist – Civilian version) measures, significant findings remained only for the right globus pallidus with anticorrelation in bilateral temporal occipital fusiform cortex, occipital fusiform gyrus, lingual gyrus, and cerebellum, as well as the right occipital pole. No group differences were found for the default mode network. Although reduced FC was found in the fronto-parietal network in the TBI group, between-group differences were nonsignificant after the ANCOVA. Conclusions: FC of the globus pallidus is altered years after exposure to blast related TBI. Future studies are necessary to explore the trajectory of changes in FC in subcortical regions after blast TBI, the effects of isolated versus repetitive blast-related TBI, and the relation to long-term outcomes in veterans. (JINS, 2016, 22, 631–642)

Outcome of moderate to severe traumatic brain injury (TBI) includes impaired emotion regulation. Emotion regulation has been associated with amygdala and rostral anterior cingulate (rACC). However, functional connectivity between the two structures after injury has not been reported. A preliminary examination of functional connectivity of rACC and right amygdala was conducted in adolescents 2 to 3 years after moderate to severe TBI and in typically developing (TD) control adolescents, with the hypothesis that the TBI adolescents would demonstrate altered functional connectivity in the two regions. Functional connectivity was determined by correlating fluctuations in the blood oxygen level dependent (BOLD) signal of the rACC and right amygdala with that of other brain regions. In the TBI adolescents, the rACC was found to be significantly less functionally connected to medial prefrontal cortices and to right temporal regions near the amygdala (height threshold T = 2.5, cluster level p < .05, FDR corrected), while the right amygdala showed a trend in reduced functional connectivity with the rACC (height threshold T = 2.5, cluster level p = .06, FDR corrected). Data suggest disrupted functional connectivity in emotion regulation regions. Limitations include small sample sizes. Studies with larger sample sizes are necessary to characterize the persistent neural damage resulting from moderate to severe TBI during development. (JINS, 2013, 19, 1–14)

Explosive blast is a frequent cause of traumatic brain injury (TBI) among personnel deployed to Afghanistan and Iraq. Functional magnetic resonance imaging (fMRI) with an event-related stimulus-response compatibility task was used to compare 15 subjects with mild, chronic blast-related TBI with 15 subjects who had not experienced a TBI or blast exposure during deployment. Six TBI subjects reported multiple injuries. Relative to the control group, TBI subjects had slightly slower responses during fMRI and increased somatic complaints and symptoms of post-traumatic stress disorder (PTSD) and depression. A between-group analysis indicated greater activation during stimulus-response incompatibility in TBI subjects within the anterior cingulate gyrus, medial frontal cortex, and posterior cerebral areas involved in visual and visual-spatial functions. This activation pattern was more extensive after statistically controlling for reaction time and symptoms of PTSD and depression. There was also a negative relationship between symptoms of PTSD and activation within posterior brain regions. These results provide evidence for increased task-related activation following mild, blast-related TBI and additional changes associated with emotional symptoms. Limitations of this study include no matching for combat exposure and different recruitment strategies so that the control group was largely a community-based sample, while many TBI subjects were seeking services. (JINS, 2012, 18, 89–100)