Emotional intensity and visual imagery in trauma nightmares map to posterior hippocampus connectivity

Distressing dreams or nightmares about a traumatic experience are common among trauma-exposed individuals and contribute to the maintenance of posttraumatic stress disorder (PTSD) symptoms. Like other intrusive reexperiencing symptoms, trauma-related nightmares are characterized by vivid sensory details and heightened emotional intensity. However, little is known about their underlying neurobiology, and whether it overlaps with that of diurnal reexperiencing symptoms. Therefore, this study aimed to elucidate neurobiological correlates of the phenomenology of trauma-related nightmares. Sixty-six trauma-exposed adults (54 female) completed daily ecological momentary assessments (EMAs) of the phenomenological properties of their trauma-related nightmares for two weeks, as well as resting-state functional magnetic resonance imaging. Pearson correlations examined associations between nightmare properties and functional connectivity within two a priori circuits previously implicated in trauma-related intrusions and episodic memory: 1) an affective circuit between the anterior hippocampus (aHPC) and amygdala (Amyg), and 2) a sensory circuit between the posterior hippocampus (pHPC) and visual cortex (VC). There were no significant associations between nightmare properties and aHPC-Amyg connectivity. In contrast, stronger pHPC-VC connectivity was associated with greater visual detail and emotional intensity of nightmares. These findings align with the established roles of the pHPC and VC in the detailed experience of episodic memory and suggest a novel role for these regions in the affective features of trauma nightmares. Overall, these findings provide support for overlapping neural correlates of the properties of trauma nightmares and diurnal reexperiencing symptoms. They offer additional evidence for a pHPC-VC circuit as a promising neurotherapeutic target for trauma reexperiencing symptoms.