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Maturation of motility and motor inhibition in rapid-eye-movement sleep
J Kohyama1, M Shimohira, Y Iwakawa
1Department of Pediatrics, Faculty of Medicine, Tokyo Medical and Dental University, Japan.
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.
Study Design:
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.
Conclusion:
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.
Insights
The tonic inhibition index, measuring motor inhibition during REM sleep, increases with age in children. This new index indicates the maturation of the inhibitory system in early childhood.
Area of Science:
- Neuroscience
- Developmental Biology
- Sleep Medicine
Background:
- Motor inhibition is crucial for sleep quality and development.
- Rapid eye movement (REM) sleep is characterized by muscle atonia, but also contains movements.
- Understanding age-related changes in motor control during sleep provides insights into neurodevelopment.
Purpose of the Study:
- To investigate age-related changes in gross movements and phasic mentalis muscle activity (PMMA) during REM sleep.
- To introduce and validate a new index for quantifying motor inhibition maturation.
- To correlate this index with the development of the inhibitory system in children.
Main Methods:
- Cross-sectional polysomnography in 87 healthy children (premature to preadolescent).
- Analysis of gross movements and PMMA.
- Introduction of a novel 'tonic inhibition index' based on PMMA duration.
Main Results:
- Gross movements and long PMMA decreased with age.
- Short PMMA and the tonic inhibition index increased with age.
- The tonic inhibition index showed the highest correlation with age and reached adult levels by 6 years.
Conclusions:
- The tonic inhibition index reflects the maturation of the inhibitory system during REM sleep.
- Motor inhibition during REM sleep develops throughout early childhood.
- The tonic inhibition index is a valuable quantitative measure for assessing inhibitory system maturity.