Interrelationships between rapid eye and body movements during sleep: polysomnographic examinations of infants including premature neonates.

Myoclonic twitching and rapid eye movements (REMs) are believed to occur in close association in animals; but, there have been few studies on their interrelations in humans. Polysomnograms were made from 33 normal infants of 34-84 conceptional weeks of age in order to observe the developmental aspect of the relation between twitching and REMs. We examined the small body movements (BMs), which appeared to be equivalent to twitches in animals and calculated the percentage of BMs that occurred together with the REM bursts in comparison to the total number that occurred during active REM sleep (% BMs in REM bursts). Polysomnograms were also obtained from 5 infant patients whose pathophysiologies were considered to be due to brain-stem immaturity. Whereas the values showed abrupt decreases during early infancy, nearly reaching 0, for the normal infants, they were high in some of the patients' records. These results suggest that few BMs occur during REMs in humans as opposed to animals. The maturation of inhibitory mechanisms, which are located in the brain-stem and act during REMs, may account for the rapid decrease of % BMs in REM bursts during early infancy. Increases of this index may reflect delayed brain-stem maturation.