Bodily stimulation during rapid eye movement sleep: effects of muscle and vestibular cueing on lucid dreaming.

Study Objectives: Sensory stimulation during rapid eye movement (REM) sleep has been proposed as a method to induce lucidity, yet most approaches rely on distal sensory modalities such as light and sound. We explored whether bodily stimulation targeting the muscle and vestibular systems differentially influences dream incorporation and lucid awareness during REM sleep. Methods: 28 participants were assigned to electrical muscle stimulation (EMS) or galvanic vestibular stimulation (GVS) and completed a 2-week cognitive training protocol including dream journaling, reality checks, and association training, followed by two counterbalanced morning naps. One in the stimulation and one in the control condition, during which cues were delivered during REM sleep. Lucidity was assessed using external dream-report ratings and Dream Lucidity Questionnaire scores. Results: Neither EMS nor GVS significantly increased direct or indirect dream incorporation relative to Control. EMS did not significantly increase lucidity. In contrast, GVS was associated with higher externally rated lucidity and higher Dream Lucidity Questionnaire-7 scores than Control. Lucidity rates were high across EMS conditions, suggesting possible contributions of cognitive training, expectancy, and baseline lucid dream frequency. Conclusions: Targeted stimulation of bodily systems during REM sleep may differentially influence dream experience. While somatosensory stimulation showed limited effects, vestibular stimulation was associated with increased lucid awareness despite minimal explicit incorporation into dream content. These findings suggest that modulation of bodily self-processing during REM sleep may influence reflective awareness independently of direct sensory incorporation. Non-invasive vestibular stimulation may therefore represent a promising approach for investigating mechanisms of lucid awareness during sleep.