Maturation of motility and motor inhibition in rapid-eye-movement sleep.
OBJECTIVE
To describe the age-related changes in the number of movements in rapid eye movement (REM) sleep, and to quantify the functional maturation of motor inhibition.


METHODS
Gross movements, phasic mentalis muscle activity (PMMA), and a new index that expressed the shortness of PMMA (the proportion of short PMMA among all PMMA) were examined cross-sectionally in 87 healthy children from premature babies to preadolescents by means of a single (all-night) polysomnography.


RESULTS
The incidence of gross movements and long PMMA decreased with age, whereas that of short PMMA increased with age. The new index exhibited an age-related increase, with the highest correlation with age among sleep parameters examined, and reached an adult level after 6 years of age.


CONCLUSIONS
We found that the age-related reduction of PMMA duration, which was expressed by a new index, occurred in parallel with the maturation of the inhibitory system that is tonically activated during REM sleep. We named this index the tonic inhibition index and concluded that the neuronal system involved in motor inhibition during REM sleep was still maturing during early childhood. We propose the tonic inhibition index as a useful quantitative indicator for the maturity of the inhibitory system.
Kohyama
J
J
Department of Pediatrics, Faculty of Medicine, Tokyo Medical and Dental University, Japan.
Shimohira
M
M
Iwakawa
Y
Y
D000293:Adolescent; D000375:Aging / Q000502:physiology*; D002648:Child; D002675:Child, Preschool; D005133:Eye Movements / Q000502:physiology; D005260:Female; D006801:Humans; D007223:Infant; D008297:Male; D009046:Motor Neurons / Q000502:physiology; D009132:Muscles / Q000502:physiology; D009433:Neural Inhibition / Q000502:physiology; D017286:Polysomnography; D012895:Sleep, REM / Q000502:physiology*