Associations of Racial Discrimination with Resting-state Network Topology: A Mechanism for Post-traumatic Sensory Disruptions

Background: Racial discrimination (RD) is a chronic stressor associated with increased risk for post-traumatic stress disorder (PTSD), a disorder associated with disruptions in neural network organization. However, the neural mechanisms linking RD to PTSD remain unclear. We examined whether RD is associated with network organization metrics, including modularity and clustering coefficient (CC), and whether network metrics influenced associations between RD and PTSD symptoms. Methods: Ninety adult (age range, 18-62) Black American women recruited for the Grady Trauma Project completed resting-state MRI along with measures of RD, trauma exposure and PTSD symptom severity. Network topology was examined for each of seven resting-state networks; adjacency matrices of each network were used to derive network modularity and CC. Partial correlations were conducted with RD and network metrics with covariates of age, trauma exposure and systemic inequities. Metrics that showed significant associations with RD were entered into moderation analyses with PTSD symptom clusters. Results: Greater RD exposure was associated with lower CC of the somatomotor network (SMN, r=-.318, p = .003). Moderation analysis revealed that RD associated with PTSD re-experiencing symptom severity at relatively lower (≤.48) [B=.58, CI (.22, .95), t = 3.20, p =.002] SMN CC values; this relationship was not observed at higher CC values ( p s>.05). Conclusion: Greater RD linked to lower clustering within the SMN, reflecting a shift toward more distributed network organization. Lower SMN clustering moderated associations between RD and PTSD re-experiencing symptoms. Findings suggest that more frequent RD may disturb the organization of networks responsible for the integration of external sensory and internal visceral signals, which, in turn, may influence the development of PTSD reliving phenomena.