A neurophysiological study of sleep paralysis in narcoleptic patients

Abstract

Behavioral response by pressing a switch placed in the hand and EEG arousal response to external stimuli (calling the subject by name 3–5 times at short intervals) were studied in the REM period in nocturnal sleep. Subjects consisted of eight normal controls and eight narcoleptics with sleept paralysis and other narcoleptic symptoms in addition to sleep attacks. All the vocal stimuli, with a few exceptions, were perceived by the subjects. Narcoleptics and controls, when stimulated in the REM period occurring more than 1 h after the sleep onset (the non sleep-onset REM period), responded to most of the stimuli by pressing the switch. In the REM period occurring at the sleep onset (the sleep-onset REM period), in which narcoleptics experienced sleep paralysis, they frequently failed to show a behavioral response (statistically significant). EEG arousal response was more marked in the controls than in the narcoleptics. In the narcoleptics it was more prominent in the non sleep-onset REM period than in the sleep-onset REM period. Based on these findings it is suggested that a dissociation between perception or consciousness level and somatic motor function occurring in narcoleptics in the sleep-onset REM period produces sleep paralysis. Possible neurophysiological mechanisms related to the occurrence of this dissociation in the sleep-onset REM period and of this sleep state in narcoleptics are discussed.