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Published on: September 22, 2023
Jaw-opening reflex and corticobulbar motor excitability changes during quiet sleep in non-human primates
Dongyuan Yao1, Gilles J Lavigne, Jye-Chang Lee
1Centre for Sensory-Motor Interaction, Department of Health Science and Technology, Aalborg University, Aalborg, Denmark.
Study Objective:
To test the hypothesis that the reflex and corticobulbar motor excitability of jaw muscles is reduced during sleep.
Design:
Polysomnographic recordings in the electrophysiological study.
Setting:
University sleep research laboratories.
Participants And Interventions:
The reflex and corticobulbar motor excitability of jaw muscles was determined during the quiet awake state (QW) and quiet sleep (QS) in monkeys (n = 4).
Measurements And Results:
During QS sleep, compared to QW periods, both tongue stimulation-evoked jaw-opening reflex peak and root mean square amplitudes were significantly decreased with stimulations at 2-3.5 × thresholds (P < 0.001). The jaw-opening reflex latency during sleep was also significantly longer than during QW. Intracortical microstimulation (ICMS) within the cortical masticatory area induced rhythmic jaw movements at a stable threshold (≤ 60 μA) during QW; but during QS, ICMS failed to induce any rhythmic jaw movements at the maximum ICMS intensity used, although sustained jaw-opening movements were evoked at significantly increased threshold (P < 0.001) in one of the monkeys. Similarly, during QW, ICMS within face primary motor cortex induced orofacial twitches at a stable threshold (≤ 35 μA), but the ICMS thresholds were elevated during QS. Soon after the animal awoke, rhythmic jaw movements and orofacial twitches could be evoked at thresholds similar to those before QS.
Conclusions:
The results suggest that the excitability of reflex and corticobulbar-evoked activity in the jaw motor system is depressed during QS.
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