Post-traumatic stress symptoms are associated with altered working memory circuits and periaqueductal gray pathways in people with chronic pain

ABSTRACT: Chronic pain and post-traumatic stress symptoms (PTSS) frequently co-occur. However, how they interact in the brain to influence cognition and emotion is not well understood. In this study, we examined how PTSS affects working memory-related networks during an N-back task. In addition, we examined how these networks interact with subcortical threat regions and influence working memory and pain symptoms. Fifty-three chronic low back pain participants completed the N-back task during fMRI. Brain activation was analyzed in relation to PTSS as both a continuous measure and a high-versus-low group, using whole-brain parcellation across task loads (FDR corrected). We also examined whether abnormally activated regions were functionally connected to periaqueductal gray subregions, the amygdala, or hippocampus, and how these connections related to PTSS. Although higher PTSS did not affect task performance, it was associated with reduced activation in dorsal and inferior lateral frontal regions during the 3-back condition. Post-traumatic stress symptoms were also associated with increased functional connectivity between the dorsolateral prefrontal cortex and periaqueductal gray, but not with the amygdala or hippocampus. Reduced prefrontal activations and high connectivity with periaqueductal gray predicted higher depression and catastrophizing symptoms. Thus, in chronic pain, PTSS selectively disrupts prefrontal circuits, suggesting that higher trauma symptoms interact with prefrontal circuits when cognitive demand is high. Post-traumatic stress symptoms strengthen coupling between prefrontal regions and brainstem threat/pain circuits, suggesting cognitive-affective coupling. These neural alterations occur even when working memory performance is intact and are linked to higher depression and pain catastrophizing. Larger studies are needed to confirm and clarify these mechanisms.