Default Mode Network Subsystems Are Differentially Disrupted in Posttraumatic Stress Disorder

Abstract

BackgroundPosttraumatic stress disorder (PTSD) is a psychiatric disorder characterized by debilitating re-experiencing, avoidance, and hyperarousal symptoms following trauma exposure. Recent evidence suggests that individuals with PTSD show disrupted functional connectivity in the default mode network, an intrinsic network that consists of a midline core, a medial temporal lobe (MTL) subsystem, and a dorsomedial prefrontal cortex (PFC) subsystem. The present study examined whether functional connectivity in these subsystems is differentially disrupted in PTSD. MethodsSixty-nine returning war veterans with PTSD and 44 trauma-exposed veterans without PTSD underwent resting-state functional magnetic resonance imaging. To examine functional connectivity, seeds were placed in the core hubs of the default mode network, namely the posterior cingulate cortex (PCC) and anterior medial PFC, and in each subsystem. ResultsCompared to control subjects, individuals with PTSD had reduced functional connectivity between the PCC and the hippocampus, a region of the MTL subsystem. Groups did not differ in connectivity between the PCC and dorsomedial PFC subsystem or between the anterior medial PFC and any region within either subsystem. In the PTSD group, connectivity between the PCC and hippocampus was negatively associated with avoidance/numbing symptoms. Examination of the MTL and dorsomedial PFC subsystems revealed reduced anticorrelation between the ventromedial PFC seed of the MTL subsystem and the dorsal anterior cingulate cortex in the PTSD group. ConclusionsOur results suggest that selective alterations in functional connectivity in the MTL subsystem of the default mode network in PTSD may be an important factor in PTSD pathology and symptomatology.