Dream incorporation and subsequent memory change after learning and waking reactivation

Abstract

Dreams often incorporate recent waking experiences, but whether the relationship between dream content and subsequent memory depends on the state of the memory before sleep remains unclear. In this exploratory study, fifteen participants learned novel word-definition-image associations across a four-day home-based protocol. Dream reports were collected after serial awakenings following initial learning and again after an incomplete reminder designed to reactivate the memory. Dream incorporations were classified as explicit, comprising recognizable references to the learned material or experimental procedure, or semantic/thematic, reflecting conceptual associations with the learned material. Following initial learning, greater explicit task-related dream incorporation was associated with greater subsequent improvement in word recall. In contrast, following memory reactivation, greater explicit and total task-related incorporation was associated with lower subsequent memorychange scores for both words and definitions. Phase-by-incorporation analyses confirmed that this relationship differed between phases for word recall, whereas the corresponding interactions for definition recall did not reach significance. These findings suggest that the relationship between dream incorporation and later memory may depend on the state of the memory before sleep, and that dream reports may provide a behavioral window into both post-learning and post-reactivation memory processing.