Breaking the circuit: Reduced cerebello-thalamo-cortical functional connectivity during traumatic memory retrieval in PTSD and its dissociative subtype

Traumatic memory retrieval is clinically characterized by vivid sensations, motoric re-enactments, temporal discontinuity and perceptual disorientation, which collectively contribute to a felt sense of reliving the past. While several studies have examined functional connectivity alterations in post-traumatic stress disorder (PTSD), no study to date has employed unrestricted data-driven methodology to investigate the overarching whole-brain connectome characteristic of traumatic memory retrieval. As a direct follow-up to Shaw et al. (2023), the present study employed a whole-brain region of interest (ROI) to ROI analysis during the retrieval of neutral and traumatic memory in 90 participants, 65 with PTSD and its dissociative subtype (PTSD+DS) and 25 trauma-exposed controls. Striking hypoconnectivity patterns emerged within cerebrocerebellar and basal ganglia-cerebellar circuits in both PTSD and PTSD+DS during traumatic memory retrieval only, where the cerebellum exhibited a segregated topology and a breakdown of long-range cortical connections. PTSD+DS was uniquely characterized by basal ganglia-occipital hypoconnectivity and brainstem-cerebellar hyperconnectivity. Further, a brain-behaviour factor analysis revealed that distinct factors characterizing dissociation aligned with unique cerebrocerebellar functional connectivity patterns. These findings suggest a disruption to vertical integration (brainstem-cerebellum-thalamus-cortex and cerebellum-basal ganglia) during traumatic memory retrieval, where cerebellar-based predictive processes may be markedly altered.