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Background: Traumatic brain injury (TBI) is one of the most prevalent injuries in the military with mild traumatic brain injury (mTBI) accounting for approximately 70-80 % of all TBI. TBI has been associated with diffuse and focal brain changes to structures and networks underlying cognitive-emotional processing. Although the anterior cingulate cortex (ACC) plays a critical role in emotion regulation and executive function and is susceptible to mTBI, studies focusing on ACC resting state functional connectivity (rs-fc) in Veterans are limited., Methods: Veterans with mTBI (n = 49) and with no history of TBI (n = 25), ages 20-54 completed clinical assessments and an 8-minute resting state functional magnetic resonance imaging (rs-fMRI) on a 3 T Siemens scanner. Imaging results were analyzed with left and right ACC as seed regions using SPM8. Regression analyses were performed with time since injury., Results: Seed-based analysis showed increased connectivity of the left and right ACC with brain regions including middle and posterior cingulate regions, preceneus, and occipital regions in the mTBI compared to the non-TBI group., Conclusions: The rs-fMRI results indicate hyperconnectivity in Veterans with mTBI. These results are consistent with previous studies of recently concussed athletes showing ACC hyperconnectivity. Enhanced top-down control of attention networks necessary to compensate for the microstructural damage following mTBI may explain ACC hyperconnectivity post-mTBI., (Copyright © 2020 The Author(s). Published by Elsevier B.V. All rights reserved.)

Traumatic brain injury (TBI) is one of the most prevalent forms of morbidity in veterans and service members, with mild traumatic brain injury (mTBI) being the most common. The diagnosis of mTBI in veterans is difficult because of mixed etiologies and high comorbidity with other disorders such as posttraumatic stress disorder (PTSD), depression, and substance use. Advanced neuroimaging techniques such as magnetic resonance spectroscopy (MRS) may be useful in identifying neurochemical alterations in TBI, which may aid the development of new targets for therapeutic intervention. Veterans with ( n = 53) and without a history of TBI ( n = 26) underwent single-voxel proton magnetic resonance spectroscopy ( 1 H MRS) at 3 Tesla in the anterior cingulate cortex (ACC) using a two-dimensional J -resolved point spectroscopy sequence in addition to completing a clinical battery. TBI diagnosis was made using the research version of the Ohio State University TBI Identification Method. An increased myoinositol (mI)/H 2 O ratio was observed in the ACC of the TBI group compared with the non-TBI group during the chronic stage of TBI (average of 139.7 mo after injury), which may be reflective of astrogliosis. Several metabolites in the ACC demonstrated significant associations with TBI variables, including number of TBI with loss of consciousness (LOC) and time since most severe TBI, suggesting that changes in some metabolites may be potential diagnostic and prognostic indicators. NEW & NOTEWORTHY In this study of veterans, we used a state-of-the-art neuroimaging tool to probe the neurometabolic profile of the anterior cingulate cortex in veterans with traumatic brain injury (TBI). We report significantly elevated myoinositol levels in veterans with TBI compared with those without TBI.

Studies investigating the neurochemical changes that correspond with suicidal behavior (SB) have not yielded conclusive results. Suicide correlates such as aggression have been used to explore risk factors for SB. Yet the neurobiological basis for the association between aggression and SB is unclear. Aggression and SB are both prevalent in veterans relative to civilian populations. The current study evaluated the relationship between brain chemistry in the anterior (ACC) and the posterior cingulate cortex (POC), as well as the relationship between aggression and SB in a veteran population using proton magnetic resonance spectroscopy ( 1 H-MRS). Single-voxel MRS data at 3 Tesla (T) were acquired from the ACC and POC voxels using a 2-dimensional J-resolved point spectroscopy sequence and quantified using the ProFit algorithm. Participants also completed a structured diagnostic interview and a clinical battery. Our results showed that the myoinositol (mI)/H2O ratio in the ACC and POC was significantly higher in veterans who reported SB when compared to veterans who did not. The two groups did not differ significantly with regard to other metabolites. Second, verbal aggression and SB measures positively correlated with mI/H2O in the ACC. Finally, verbal aggression mediated the relationship between mI/H2O in the ACC and SB., (Copyright © 2018 Elsevier B.V. All rights reserved.)