Homeostatic and Circadian Influences on Dreaming: NREM Mentation During a Short Daytime Nap

Abstract

It has long been known that dream recall, along with various other features of dreaming, changes as a function of time of night. Yet the processes which might account for these time-dependent variations remain obscure. Here we assess the contribution of homeostatic and circadian factors to the generation of NREM mentation across the diurnal cycle. Assuming that previously reported time-of-night mentation effects are primarily driven by a circadian activation cycle which approximates the core body temperature (CBT) rhythm, it was hypothesized that more content would be reported from daytime nap awakenings as compared to night awakenings. Afternoon Nap reports were compared to previously-collected nocturnal reports from Circadian Nadir and Late Morning time points. Contrary to our hypotheses, both amount of mentation reported and propensity to report any mentation at all were lower in Nap as compared to Late Morning reports. A purely circadian influence following the CBT cycle is inadequate to explain this pattern of mentation production.