Hypnagogic and hypnopompic hallucinations during sleep paralysis: Neurological and cultural construction of the night-mare

Hypnagogic and hypnopompic experiences (HHEs) accompanying sleep paralysis (SP) are often cited as sources of accounts of supernatural nocturnal assau lts and paranormal experiences. Descriptions of such experiences are remark ably consistent across time and cultures and consistent also with known mec hanisms of REM states. A three-factor structural model of HHEs based on the ir relations both to cultural narratives and REM neurophysiology is develop ed and tested with several large samples. One factor, labeled Intruder, con sisting of sensed presence, fear, and auditory and visual hallucinations, i s conjectured to originate in a hypervigilant state initiated in the midbra in. Another factor, Incubus, comprising pressure on the chest, breathing di fficulties, and pain, is attributed to effects of hyperpolarization of moto neurons on perceptions of respiration. These two factors have in common an implied alien "other" consistent with occult narratives identified in numer ous contemporary and historical cultures. A third factor, labeled Unusual B odily Experiences, consisting of floating/flying sensations, out-of-body ex periences, and feelings of bliss, is related to physically impossible exper iences generated by conflicts of endogenous and exogenous activation relate d to body position, orientation, and movement, implications of this last fa ctor for understanding of orientational primacy in self-consciousness are c onsidered. Central features of the model developed here are consistent with recent work on hallucinations associated with hypnosis and schizophrenia. (C) 1999 Academic Press.