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Phasic motor activity reduction occurring with horizontal rapid eye movements during active sleep in human
J Kohyama1, M Shimohira, T Hasegawa
1Department of Pediatrics, Faculty of Medicine, Tokyo Medical and Dental University, Japan.
Insights
Active sleep in children shows a phasic reduction in muscle activity linked to rapid eye movements (REMs). This motor inhibition, observed even in brain-damaged patients, suggests a brainstem origin for REM-related muscle control.
Area of Science:
- Neuroscience
- Sleep Medicine
- Developmental Pediatrics
Background:
- Active sleep is characterized by rapid eye movements (REMs) and distinct physiological patterns.
- Phasic muscle activity changes during REM sleep are crucial for understanding sleep regulation.
- Previous research in animals suggests brainstem mechanisms control muscle atonia during REM sleep.
Purpose of the Study:
- To investigate the phasic reduction of motor activity associated with REMs during active sleep in children.
- To determine the origin and characteristics of REM-related muscle inhibition in humans.
- To explore the relationship between REM sleep phenomena and motor control in both healthy children and those with brain damage.
Main Methods:
- Electromyography (EMG) was used to measure intercostal and mentalis muscle activity in 15 children (12 healthy, 3 with severe brain damage).
- Averaging techniques were applied to analyze muscle activity in relation to REM onset and mentalis muscle twitches.
- Latency and duration of muscle activity changes were calculated for healthy subjects.
Main Results:
- A significant decrease in intercostal muscle activity was observed following REM onset in healthy children (mean latency 37.1 ms, duration 225.9 ms).
- This REM-related muscle inhibition was also present in children with severe brain damage, supporting a brainstem origin.
- A REM-related reduction in mentalis muscle activity occurred before REM onset (mean onset 59.1 ms prior, duration 230.2 ms), alongside a twitch-related decrease in REM activity.
Conclusions:
- Phasic motor inhibition occurs during REM sleep in humans, consistent with findings in animal models.
- The observed muscle activity patterns suggest a brainstem generator controlling REMs, motor inhibition, and excitation (including twitches) during active sleep.
- These findings contribute to understanding the neural control of sleep and motor behavior in children, including those with neurological impairments.
Abstract:
We describe the phasic reduction of motor activity occurring with horizontal rapid eye movements (REMs) during active sleep in 15 children (12 healthy children and 3 patients with severe brain damage). A REM-related decrease in intercostal muscle activity was demonstrated by averaging integrated surface electromyograms. In the healthy subjects, this reduction had a mean latency from the REM onset of 37.1 ms and a duration of 225.9 ms. This phenomenon was also observed in the 3 patients who had lost cerebral function. We hypothesized a brainstem origin for the effect. A REM-related mentalis muscle activity loss, detected by averaging mentalis muscle twitches, was observed in 10 healthy children among the subjects. This loss began at 59.1 ms before the onset of REMs and lasted for 230.2 ms on average. In addition, a transient decrease in integrated REM activity surrounding mentalis muscle twitches (a twitch-related reduction of REMs) was observed. We discuss the similarity between REM-related phasic reduction of muscle activity obtained for intercostal and mentalis muscles and pontogeniculo-occipital (PGO) wave-related inhibitory postsynaptic potentials reported for feline lumbar and trigeminal motoneurons, respectively. We then assume the presence of a phasic event generator, functioning during active sleep in healthy humans, which triggers at least three generators; that is, the generator of PGO waves (or REMs), motor inhibition, and of motor excitation including muscle twitches.