Are internally-cued and externally-cued intrusions distinct post-traumatic stress symptom dimensions? A pilot study...

Intrusion symptoms, a core dimension of PTSD, have recently been categorized into internally-cued intrusions (I-Int; comprising re-experiencing symptoms) and externally-cued intrusions (E-Int; comprising reactivity to external reminders), but it remains unclear whether these two symptom clusters have different neural underpinnings. We utilized the triple brain network model (comprising the default mode, central executive, and salience networks) to investigate this issue. We initially recruited 50 COVID-19 survivors from Wuhan (final sample N = 46), who underwent resting-state functional magnetic resonance imaging scans and completed self-report assessments. Based on intrusion symptom scores, participants were stratified into E-Int-positive and E-Int-negative subgroups, as well as I-Int-positive and I-Int-negative subgroups. Key findings revealed that within the I-Int subgroup classification, static triple-network analysis demonstrated significantly attenuated anti-correlation FC between the DMN and CEN in the I-Int positive group compared to the I-Int negative group. These differences were consistently replicated in dynamic states 2 (the 'Segregated State') and 5 (the 'Globally Hyper-connected State'). Within the E-Int subgroup classification, the E-Int positive group exhibited higher FC between the DMN-SN specifically in dynamic state 4 (the 'Transitional State'). Correlation analyses further indicated that I-Int scores within the I-Int positive subgroup were positively associated with DMNCEN FC in both static model and state 2 of dynamic model. These findings suggest that the two types of intrusions may have different neural underpinnings, which enhances our understanding of post-traumatic stress symptoms and offers potential directions for future targeted therapies. However, given the relatively small sample size, these findings are preliminary and require replication in larger cohorts with greater symptom severity.