Phasic events of REM sleep: phenomenology of middle ear muscle activity and periorbital integrated potentials in the same normal population.

Both periorbital integrated potentials (PIPs) and middle ear muscle activity (MEMAs) were recorded in a sample of normal male veterans. Activity measures were constructed for each REM period and for the 10 min preceding and following each REM period. PIPs and MEMAs displayed high levels of internight reliability. PIPs were more abundant than MEMAs; in REM the average PIP rate was almost 8 times the average MEMA rate. Within REM, the proportion of MEMAs and PIPs with concurrent eye movement activity was very similar, 66 and 70%, respectively. Both PIPs and MEMAs had higher rates within REM than within NREM. NREM PIP activity was similar both before and after the REM period, whereas NREM MEMA activity was higher before the REM period than after the REM period. Within REM, the distribution of PIPs and MEMAs was similar for REM periods exceeding 30 min. Within-night trends could nor be established for MEMAs due to limitations of the recording technique; PIPs, however, were generally highest in the middle of the night but still higher at the end of the night than at the beginning. Correlations with psychometric test data showed PIP rate in REM to be related to the psychoticism scale of the Minnesota Multiphasic Personality Inventory and MEMA rate in REM to be inversely related to the Barron Ego Strength scale. No associations were found between the psychometric data and measures of PIP and MEMA leakage from REM into NREM. The potential for pathological intrusion of REM phasic events into the waking stage might be conceptualized in terms of a general ungating of activity with PIP and MEMA rates increasing in both NREM and REM alike.