Investigating dreams by strategically presenting sounds during REM sleep to reactivate waking experiences

Dreams may partially reflect the memory reorganizing that occurs nightly to improve the usefulness of what we learn each day. However, solid evidence has yet to link dreaming with adaptive overnight memory processes. Dream research faces several challenges, including the difficulty of experimentally controlling dream content and the susceptibility of dream reports to distortion and forgetting upon awakening. Memory consolidation can be systematically manipulated using Targeted Memory Reactivation (TMR), whereby sensory stimulation during sleep triggers processing of previously acquired memories. Stimuli presented during sleep can be incorporated into dreams, but how reactivated memories might influence dream content is still unknown. This study aims to use TMR to strategically influence dreams. In the evening, participants performed two distinct tasks designed to be readily incorporated into dreams. Each task was associated with a unique sound and entailed a unique respiratory signature designed to be objectively verifiable during sleep. The association between each task and sound was further reinforced in a conditioning phase just prior to sleep. When a participant entered REM sleep, the experimenter presented one of the two sounds, thus attempting to induce dreams related to the associated task. Dream reports revealed incorporation of task elements that were high for both tasks, and relatively higher for the cued task. Dreaming of a task was linked with decreased negative valence and increased creativity. We conclude that this approach to dream curation provides a novel way to investigate the influence of dreaming on memory storage.