PHASIC MUSCLE-ACTIVITY DURING REM-SLEEP IN INFANCY NORMAL MATURATION AND CONTRASTIVE ABNORMALITY IN SIDS ALTE AND WEST SYNDROME

The generation of phasic muscle activity during REM sleep is regulated by the brainstem. We proposed two sleep indices for phasic muscle act ivity during REM sleep, and examine their usefulness in assessing norm al brainstem maturation and functional brainstem impairment during inf ancy. One - the dissociation index (DI) - seems to reflect maturation of the tonic inhibitory system functioning during REM sleep, and the o ther - % body movements in REMs bursts (%BMs-R) - to reflect that of t he phasic one. In normal infants, DI showed a gradual, linear and sign ificant increase with age, whereas %BMs-R showed a gradual and signifi cant decrease with age. In infants with sudden infant death syndrome ( SIDS) and one who had experienced apparent life-threatening events (AL TE), the DI values were lower than those in controls, although %BMs-R values were identical in the controls. In contrast, DI was variable in infants with West syndrome (WS), while %BMs-R exceeded normal values. The tonic inhibitory system seemed to be specifically involved in SID S and ALTE, but the phasic inhibitory one in WS. Anatomical difference s between these inhibitory systems are also discussed.