Masseter EMG activity during sleep and sleep bruxism

Area of Science:

• Neuroscience
• Sleep Medicine
• Oromotor Function

Background:

• The masseter muscle, crucial for mastication, exhibits reduced but present electromyographic (EMG) activity during sleep.
• This activity is inhomogeneous and influenced by sleep stages (NREM, REM) and arousal levels.
• Specific motor events like rhythmic masticatory muscle activity (RMMA) occur during sleep, with sleep bruxism representing an exaggerated form.

Purpose of the Study:

• To review and synthesize current knowledge on masseter EMG activity during sleep.
• To explore the neural substrates underlying masseter muscle behavior across different sleep states.
• To elucidate the potential mechanisms contributing to sleep bruxism (SB).

Main Methods:

• Review of existing literature on masseter muscle EMG during sleep.
• Analysis of neural control mechanisms for oromotor behaviors during wakefulness and sleep.
• Examination of factors influencing motoneuron excitability and motor output.

Main Results:

• Masseter EMG activity during sleep is characterized by low-level, inhomogeneous signals influenced by arousal fluctuations.
• Neural substrates for NREM and REM sleep modulate masseter motoneuron excitability.
• Sleep bruxism involves exaggerated RMMA, potentially driven by common neural circuits and facilitatory inputs during arousals.

Conclusions:

• The diverse patterns of masseter EMG activity during sleep likely result from a combination of neural factors.
• Quantitative, spatial, and temporal neural inputs to trigeminal motoneurons, modulated by sleep regulatory systems, shape these patterns.
• Further research is needed to fully understand the specific neural circuits governing sleep bruxism.