Abstract
Resting-state functional connectivity (rsFC) is an emerging means of understanding the neurobiology of combat-related post-traumatic stress disorder (PTSD). However, most rsFC studies to date have limited focus to cognitively related intrinsic connectivity networks (ICNs), have not applied data-driven methodologies or have disregarded the effect of combat exposure. In this study, we predicted that group independent component analysis (GICA) would reveal group-wise differences in rsFC across 50 active duty service members with PTSD, 28 combat-exposed controls (CEC), and 25 civilian controls without trauma exposure (CC). Intranetwork connectivity differences were identified across 11 ICNs, yet combat-exposed groups were indistinguishable in PTSD vs CEC contrasts. Both PTSD and CEC demonstrated anatomically diffuse differences in the Auditory Vigilance and Sensorimotor networks compared to CC. However, intranetwork connectivity in a subset of three regions was associated with PTSD symptom severity among executive (left insula; ventral anterior cingulate) and right Fronto-Parietal (perigenual cingulate) networks. Furthermore, we found that increased temporal synchronization among visuospatial and sensorimotor networks was associated with worse avoidance symptoms in PTSD. Longitudinal neuroimaging studies in combat-exposed cohorts can further parse PTSD-related, combat stress-related or adaptive rsFC changes ensuing from combat.
Highlights
Military service members and veterans who have experienced extreme trauma in military combat are especially vulnerable to post-traumatic stress disorder (PTSD) (Kilpatrick et al, 2013)
While PTSD and combat-exposed controls (CEC) groups served an equivalent number of OEF/OIF deployments (P = 0.45), selfreported combat experiences as measured by Deployment Risk and Resilience Inventory Combat Experiences (DRRI-C) were significantly higher (P = 0.003) in PTSD (53 ± 16) compared to CEC (43 ± 15); the baseline score of DRRI-C is 23, which indicates no stereotypical combat experience
While civilian control (CC) subjects were excluded if they were taking a psychotropic medication, medication status did not affect study enrollment for combatexposed groups; 58 and 3% of PTSD and CEC subjects were taking a psychotropic medication at the time of the study, respectively
Summary
Military service members and veterans who have experienced extreme trauma in military combat are especially vulnerable to post-traumatic stress disorder (PTSD) (Kilpatrick et al, 2013) Of those who served in Operation Enduring Freedom or Operation Iraqi Freedom (OEF/OIF), the population of interest in this study, disease prevalence has been estimated at 23% (Fulton et al, 2015). Psychotherapy is most effective in treating individuals with PTSD (Institute of Medicine, 2014; Kirkpatrick & Heller, 2014); between 20 and 50% of patients do not respond to firstline treatments (Schottenbauer et al, 2008). This therapeutic gap requires an improved, neurobiological understanding of PTSD (Insel et al, 2010). Resting-state functional connectivity (rsFC) provides a stable and generalizable perspective (Gratton et al, 2018) of the neurobiological mechanisms underlying psychopathology at baseline, or ‘rest’ (Menon, 2011)
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