Out-of-body experiences (OBEs) and vestibular-motor sensations during sleep paralysis share a distinct factor, with research on direct vestibular cortex stimulation producing nearly identical bodily-self hallucinations. Two online surveys of sleep paralysis experiences assessed causal relationships among vestibular-motor experiences and OBEs. Results support the hypothesis that OBEs arise from a breakdown in normal bodily-self sensation binding, with out-of-body feelings resulting from anomalous vestibular-motor experiences and preceding a specific form of autoscopic experience called out-of-body autoscopy. Vestibular and motor experiences independently contribute to OBE variance. The findings offer naturalistic explanations for phenomena superficially consistent with dualistic and supernatural intuitions.
Out-of-body experiences (OBEs) are linked to specific brain regions, but little is known about the neurochemical systems involved. Ketamine, a drug that produces dissociative effects, offers a way to study this. An online survey of 192 people found that both how often someone had used ketamine in their lifetime and whether they had OBEs while on ketamine were more strongly tied to how often they had OBEs and related experiences than other drugs were. The apparent effects of other drugs could mostly be explained by the fact that people who used them also tended to use ketamine. These findings suggest NMDA receptors play a role in OBEs.
Sleep paralysis episodes occur most often in the first two hours after going to bed, with just over a quarter happening within the first hour, though episodes can occur throughout the night with a smaller peak near normal waking time. The timing of episodes is consistent for individuals across different nights and does not depend on what time they go to bed. The results support the idea that sleep paralysis timing is controlled by processes that start at or after sleep onset and suggest that sleep paralysis may result from failing to maintain sleep during REM periods at any point in the night, rather than only at sleep onset.
A new scale, the Waterloo Sleep Experiences Scale, measures the prevalence of sleep paralysis and related hallucinoid experiences such as sensed presence, pressure, floating, and auditory or visual hallucinations. Among 870 university students, nearly 30% reported at least one sleep paralysis episode. About three-quarters of those also reported hallucinoid experiences, and over 10% experienced three or more. Fear was positively linked to hallucinoid experiences, especially sensed presence. Regression analyses suggest that sensed presence and fear are basic features of sleep paralysis that may lead to further hallucinoid experiences, particularly visual ones.