H-reflex and EMG of the mental and hyoid muscles during sleep, with special reference to narcolepsy

Abstract

The activity of the mental and hyoid muscles, and the H-reflex were examined during nocturnal sleep and daytime naps of narcoleptic and normal subjects. The continuous, tonic EMG discharges, which were observed in all subjects in the awake state, decreased in parallel with deepening of sleep but disappeared only during the rapid eye movements (REM) period, which occurred at the sleep onset in narcoleptics and late in nocturnal sleep in normal and narcoleptic subjects. During the REM period, only transient, phasic EMG discharges of low voltage were occasionally observed. The H-reflex also decreased in amplitude when the subjects fell asleep. The degree of its decrement was slight in the drowsy stage and was greater in light and deep sleep. During the REM period which occurred at the sleep onset in narcoleptics and late in nocturnal sleep in normal and narcoleptic subjects, the decrement was most prominent and consistent and the H-reflex reflex would completely disappear. The sleep onset REM period was examined in four narcoleptics, two of which experienced sleep paralysis in this period. It is concluded that sleep paralysis is not a part of the hypnagogic hallucinations often experienced by narcoleptics but a real experience of paralysis resulting from a dissociation between the level of consciousness and the somatic muscle and reflex activities in the sleep onset REM period.