Reduced cerebello-thalamo-cortical functional connectivity during traumatic memory retrieval in PTSD

Traumatic memory retrieval is marked by vivid sensations, temporal fragmentation and a sense of reliving the past. Here we apply an unrestricted, whole-brain connectome approach to examine neutral and traumatic memory retrieval using functional magnetic resonance imaging in 90 individuals: those with post-traumatic stress disorder (PTSD, n = 46) and its dissociative subtype (PTSD + DS, n = 19) versus trauma-exposed controls (n = 25). Both PTSD and PTSD + DS exhibited hypoconnectivity in cerebrocerebellar and basal ganglia–cerebellar circuits alongside increased intracerebellar connectivity during traumatic memory retrieval only, reflecting a segregated cerebellar topology and a breakdown in long-range cortical connections. Brainstem–cerebellar hyperconnectivity was observed in PTSD + DS relative to controls during traumatic memory retrieval and in all participants with PTSD when directly comparing traumatic versus neutral memory retrieval. PTSD + DS exhibited additional hypoconnectivity between occipital regions and the thalamus and basal ganglia. These findings suggest a disruption to subcortical–cortical ‘vertical’ integration during traumatic memory retrieval, where cerebellar-based predictive processes may be markedly altered.