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

Abstract

Abstract 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. sec001 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. sec002 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. sec003 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. Statement of Significance External stimulation during sleep is often assumed to promote lucid dreaming by becoming incorporated into dream content. This study suggests that this assumption may be incomplete. While muscle stimulation showed some incorporation without clear lucidity benefits, vestibular stimulation was associated with greater lucidity despite little explicit incorporation. These findings support the idea that different sensory systems may influence dreaming through distinct mechanisms, including effects on bodily self-processing and lucid awareness. It highlights vestibular stimulation as a promising direction for mechanistic lucid dream research and raises the broader question of whether dream incorporation is necessary for externally induced lucidity. abs5 box01 float portrait sec004 Graphical Abstract Graphical Abstract Graphical abstract illustrating the study design and main findings. Twenty-eight participants completed an adaptation nap, a 2.5-week cognitive training protocol (dream journaling, reality checks, and stimulation-based association training), and two counterbalanced morning naps with polysomnography, receiving either active REM sleep stimulation or sham stimulation. Participants were assigned to either electrical muscle stimulation (EMS; n = 13) applied to the forearm or galvanic vestibular stimulation (GVS; n = 11) applied over the mastoid processes. Neither stimulation modality produced meaningful increases in dream incorporation compared with sham. Bar graphs show that EMS did not significantly increase externally rated lucid dreaming or Dream Lucidity Questionnaire (DLQ-7) scores relative to sham, whereas GVS was associated with higher externally rated lucidity and higher DLQ-7 scores than sham. The graphical abstract concludes that vestibular stimulation may enhance lucid awareness despite minimal incorporation into dream content, suggesting that modulation of bodily self-processing during REM sleep may facilitate reflective awareness independently of direct sensory incorporation. http://www.w3.org/1999/xlink float portrait zpag074ga1.jpg float ga1 portrait graphical