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SP is a transient, conscious state of involuntary immobility occurring immediately prior to falling asleep or upon wakening and is classified as a parasomnia associated with REM (ASDA, 1990). Although individuals are unable to make gross bodily movements during SP they are able to open their eyes and subsequently to report accurately on events in their surroundings during the episode (Hishikawa & Kaneko, 1965). Approximately 25 to 40% of people report some SP experience (Cheyne, Newby- Clark, & Rueffer, in press; Fukuda, Ogilvie, Chilcott, Vendittelli, & Takeuchi, 1998; Spanos, McNulty, DuBreuil, Pires, & Burgess, 1995), although the incidence may vary across cultures (Fukuda, Miyasita, & Ishihara, 1987; Ness, 1978).
Hypnagogic and Hypnopompic Hallucinations during Sleep Paralysis: Neurological and Cultural Construction of the Night-Mare
J. Allan Cheyne, Steve D. Rueffer, and Ian R. Newby-Clark (1999)