Jaw-opening reflex and corticobulbar motor excitability changes during quiet sleep in non-human primates

Sleep. 2013 Feb 1;36(2):269-80. doi: 10.5665/sleep.2388.


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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Electroencephalography
  • Electromyography
  • Female
  • Jaw / physiology*
  • Macaca fascicularis / physiology
  • Macaca mulatta / physiology
  • Polysomnography
  • Pyramidal Tracts / physiology*
  • Reflex / physiology*
  • Sleep / physiology*
  • Sleep Stages / physiology