title: Brain network disturbance related to posttraumatic stress and traumatic brain injury in veterans.
abstract: BACKGROUND
  Understanding the neural causes and consequences of posttraumatic stress disorder (PTSD) and mild traumatic brain injury (mTBI) is a high research priority, given the high rates of associated disability and suicide. Despite remarkable progress in elucidating the brain mechanisms of PTSD and mTBI, a comprehensive understanding of these conditions at the level of brain networks has yet to be achieved. The present study sought to identify functional brain networks and topological properties (measures of network organization and function) related to current PTSD severity and mTBI.
  
  
  METHODS
  Graph theoretic tools were used to analyze resting-state functional magnetic resonance imaging data from 208 veterans of Operation Enduring Freedom, Operation Iraqi Freedom, and Operation New Dawn, all of whom had experienced a traumatic event qualifying for PTSD criterion A. Analyses identified brain networks and topological network properties linked to current PTSD symptom severity, mTBI, and the interaction between PTSD and mTBI.
  
  
  RESULTS
  Two brain networks were identified in which weaker connectivity was linked to higher PTSD re-experiencing symptoms, one of which was present only in veterans with comorbid mTBI. Re-experiencing was also linked to worse functional segregation (necessary for specialized processing) and diminished influence of key regions on the network, including the hippocampus.
  
  
  CONCLUSIONS
  Findings of this study demonstrate that PTSD re-experiencing symptoms are linked to weakened connectivity in a network involved in providing contextual information. A similar relationship was found in a separate network typically engaged in the gating of working memory, but only in veterans with mTBI.
authors.affiliation: Neuroimaging Research for Veterans Center; Department of Psychiatry, Boston University School of Medicine. Electronic address: jmsp@bu.edu.
authors.forename: Jeffrey M
authors.initials: JM
authors.lastname: Spielberg
authors.affiliation: Geriatric Research, Education and Clinical Center and Translational Research Center for TBI and Stress Disorders, VA Boston Healthcare System; Departments of Psychiatry.
authors.forename: Regina E
authors.initials: RE
authors.lastname: McGlinchey
authors.affiliation: Geriatric Research, Education and Clinical Center and Translational Research Center for TBI and Stress Disorders, VA Boston Healthcare System; Departments of Psychiatry.
authors.forename: William P
authors.initials: WP
authors.lastname: Milberg
authors.affiliation: Neuroimaging Research for Veterans Center; Radiology, Harvard Medical School, Boston, Massachusetts.
authors.forename: David H
authors.initials: DH
authors.lastname: Salat
mesh_terms: D055826:Afghan Campaign 2001-; D001921:Brain / Q000503:physiopathology*; D001930:Brain Injuries / Q000453:epidemiology*; D015897:Comorbidity; D049674:History, 21st Century; D006801:Humans; D054542:Iraq War, 2003-2011; D008279:Magnetic Resonance Imaging; D012720:Severity of Illness Index; D013313:Stress Disorders, Post-Traumatic / Q000453:epidemiology*; D014728:Veterans / Q000523:psychology*
keywords: Brain network; Graph theory; Hippocampus; Posttraumatic stress disorder; Traumatic brain injury; fMRI