Neural correlates of nightmares revisited: findings from large-scale fMRI cohorts

Study ObjectivesNightmares are linked to daytime distress and psychiatric and neurological disorders. However, knowledge about the brain regions involved in nightmare production is sparse. This study aimed to examine the relationship between nightmare frequency and the functional connectivity of the amygdala with the prefrontal cortex, which is central to emotional regulation. Additionally, the study sought to replicate previous findings on the neural correlates of nightmares using two large cohorts. Methods464 participants underwent functional and structural MRI recordings and answered questions assessing nightmare and dream recall frequency. A general linear model assessed the voxelwise correlation between the amygdala-prefrontal cortex connectivity with nightmare frequency. Additionally, regional homogeneity (ReHo) maps were calculated, high and low nightmare frequency and the entire nightmare frequency spectrum contrasts were determined while controlling for age, sex, and dream recall frequency. ResultsThe study did not find a significant correlation between nightmare frequency and amygdala-prefrontal cortex connectivity. Previous ReHo findings of group differences between high and low nightmare frequency could not be replicated. However, parametric analysis revealed an association between nightmare frequency and ReHo differences in the cerebellum. ConclusionsThis failure to confirm hypothesized and previously reported results, especially with a larger sample size, suggests a need to reevaluate the existing knowledge of the neural correlates of nightmares and consider individual differences such as personality, trauma history, and cognitive processes. Overall, our findings highlight the complexities of interpreting neuroimaging data in sleep research.