Daytime experiences shape neural activity and dream content in the sleeping brain

Abstract

Learning-related brain activity patterns are replayed during sleep, and memories of recent experiences appear in our dreams. The connection between these phenomena, however, remains unclear. We investigated whether memory reinstatement during sleep contributes to dreaming. Participants listened to audiobooks before falling asleep. We could determine which audiobook they had studied based on dream reports collected during the night. Audiobook content was also reinstated at the neural level, in high-density EEG recordings. Brain activity during rapid eye movement sleep, particularly in the high-frequency beta range, carried information about the audiobook and simultaneously benefitted memory retention. Crucially, when the learning condition was manifest in neural activity, it also emerged in dreams. Reprocessing of daytime experiences during sleep thus shapes our brain activity, our dreams, and our memories.