Strength and Temporal Variance of the Default Mode Network to Investigate Chronic Mild Traumatic Brain Injury in Service Members with Psychological Trauma

Michael N Dretsch; D Rangaprakash; Jeffrey S Katz; Thomas A Daniel; Adam M Goodman; Thomas S Denney; Gopikrishna Deshpande

doi:10.1177/1179069519833966

Strength and Temporal Variance of the Default Mode Network to Investigate Chronic Mild Traumatic Brain Injury in Service Members with Psychological Trauma

J Exp Neurosci. 2019 Mar 18:13:1179069519833966. doi: 10.1177/1179069519833966. eCollection 2019.

Authors

Michael N Dretsch^{1

2

3}, D Rangaprakash^{4

5}, Jeffrey S Katz^{2

5

6}, Thomas A Daniel², Adam M Goodman^{2

6}, Thomas S Denney^{5

6}, Gopikrishna Deshpande^{5

6}

Affiliations

¹ U.S. Army Aeromedical Research Laboratory, Fort Rucker, AL, USA.
² Department of Psychology, Auburn University, Auburn, AL, USA.
³ U.S. Army Medical Research Directorate-West, Walter Reed Army Institute for Research, Joint Base Lewis-McChord, WA, USA.
⁴ Department of Psychiatry and Biobehavioral Sciences, University of California, Los Angeles, Los Angeles, CA, USA.
⁵ AU MRI Research Center, Department of Electrical and Computer Engineering, Auburn University, Auburn, AL, USA.
⁶ Alabama Advanced Imaging Consortium, Auburn University and The University of Alabama at Birmingham, Birmingham, AL, USA.

Abstract

Background: There is a significant number of military personnel with a history of mild traumatic brain injury (mTBI) who suffer from comorbid posttraumatic stress symptoms (PTS). Although there is evidence of disruptions of the default mode network (DMN) associated with PTS and mTBI, previous studies have only studied static connectivity while ignoring temporal variability of connectivity.

Objective: To assess DMN disrupted or dysregulated neurocircuitry, cognitive functioning, and psychological health of active-duty military with mTBI and PTS.

Method: U.S. Army soldiers with PTS (n = 14), mTBI + PTS (n = 25), and healthy controls (n = 21) voluntarily completed a cognitive and symptom battery. In addition, participants had magnetic resonance imaging (MRI) to assess both static functional connectivity (SFC) and variance of dynamic functional connectivity (vDFC) of the DMN.

Results: Both the PTS and mTBI + PTS groups had significant symptoms, but only the comorbid group had significant decrements in cognitive functioning. Both groups showed less stable and disrupted neural signatures of the DMN, mainly constituting the cingulate-frontal-temporal-parietal attention network. Specifically, the PTS group showed a combination of both reduced contralateral strength and reduced unilateral variability of frontal-cingulate-temporal connectivities, as well as increased variability of frontal-parietal connectivities. The mTBI + PTS group had fewer abnormal connectives than the PTS group, all of which included reduced strength of frontal-temporal regions and reduced variability frontal-cingulate-temporal regions. Greater SFC and vDFC connectivity of the left dorsolateral prefrontal cortex (dlPFC) ↔ precuneus was associated with higher cognitive scores and lower symptom scores.

Conclusions: Findings suggest that individuals with PTS and mTBI + PTS have a propensity for accentuated generation of thoughts, feelings, sensations, and/or images while in a resting state. Compared with controls, only the PTS group was associated with accentuated variability of the frontal-parietal attention network. While there were no significant differences in DMN connectivity strength between the mTBI + PTS and PTS groups, variability of connectivity was able to distinguish them.

Keywords: Functional magnetic resonance imaging; default mode network; functional connectivity; mild traumatic brain injury; military; posttraumatic stress disorder.