Weaker functional segregation of the sensory and default mode networks in trauma-related intrusive memories

Trauma-related intrusive memories (TRIMs) are a core symptom of posttraumatic stress disorder and cause significant distress and impairment for trauma-exposed individuals due to their vivid sensory features that intrude on ongoing thought. These phenomenological properties point to a neuropathology that spans autobiographical memory, spontaneous thought, and sensory perception. The hierarchical organization of the cortex maximally segregates the default mode network (DMN), which supports autobiographical memory and ongoing thought, from the sensory cortices (SC). Accruing evidence implicates altered interactions between the DMN and SC in PTSD and TRIMs, suggesting a breakdown in this segregation. We sought to test whether diminished DMN-SC segregation, indexed by a shorter functional distance between the DMN and SC within cortical connectivity gradients, was associated with the vividness and intrusiveness of TRIMs. One-hundred eight trauma-exposed adults completed two weeks of ecological momentary assessments (EMAs) of TRIM properties followed by resting-state fMRI. Gradient analysis of cortical functional connectivity was performed to compute the Euclidean distance between resting-state networks. Pearson correlations revealed an association between a shorter DMN-SC distance and greater TRIM vividness and intrusiveness, with multivariate models indicating a specificity for intrusiveness. Importantly, the DMN-SC distance was not associated with clinician-rated symptom severity and explained unique variance above and beyond conventional functional connectivity measures. These findings suggest that a loss of functional segregation between the DMN and SC - a core organizational feature of the cortical hierarchy - is associated with the intrusive sensory vividness of TRIMs, offering insights into candidate mechanisms of and neurotherapeutic targets for intrusive trauma memories. .