Connectivity patterns in the DMN that are impacted by traumatic stress

Decreased connectivity within the default mode network (DMN) has been consistently implicated in post traumatic stress disorder (PTSD), but critical nodes through which traumatic stress changes DMN connectivity and DMN connectivity patterns that are linked to specific traumatic stress effects are not well understood. To address this, resting-state functional connectivity (rs-FConn) within the DMN was analyzed using modular and graph theory tools to characterize DMN connectivity changes brought on by single prolonged stress (SPS); a rat traumatic stress model. Results identified a set of negative edges that connect anterior and posterior DMN nodes. We refer to these as A-P edges and the anterior cingulate cortex (ACC) and rostral retrosplenial cortex (rRSC) were nodes that had the largest number of these edges. A-P edge frequency and graph connectivity measures decreased with a second fMRI scan in control rats and these decreases, and rRSC A-P edge frequency, were disrupted by SPS. Traumatic stress leads to deficits in extinction retention and to examine how DMN connectivity changed during extinction, we used correlated c-Fos levels among select DMN nodes to approximate DMN connectivity during fear/threat conditioning, and extinction learning and memory. Results suggest that SPS decreased DMN connectivity under most conditions, but enhanced DMN connectivity during extinction testing. Overall, the results of this study raise the possibility that while SPS does decrease DMN connectivity and disrupts changes in DMN connectivity brought on by a second fMRI scan, certain aspects of DMN connectivity are enhanced with SPS.