Upper airway muscle activity is reportedly elevated during slow-wave sleep (SWS) when compared to lighter sleep stages. To uncover the possible mechanisms underlying this elevation, we explored the correlation between different indices of central and reflex inspiratory drive, such as the changes in airway pressure and end-expiratory CO2, and the changes in the genioglossus (GG) and tensor palatini (TP) muscle activity accompanying transitions from the lighter N2 to the deeper N3 stage of non-rapid eye movement (NREM) sleep in healthy young adult men. Forty six GG and 38 TP continuous electromyographic recordings were obtained from 16 men [age: 20 ±2.5 (SD) years; body mass index: 22.5 ±1.8 kg/m2] during 32 transitions from NREM stages N2 to N3. GG, but not TP, activity increased following transition into N3 sleep, and the increase was positively correlated with more negative airway pressure, increased end-tidal CO2, increased peak inspiratory flow and increased minute ventilation. None of these correlations was statistically significant for TP. Complementary GG and TP single motor unit analysis revealed a mild recruitment of GG units and de-recruitment of TP units during the N2 to N3 transitions. These findings suggest that, in healthy individuals, the increased GG activity during SWS is primarily driven by reflex stimulation of airway mechanoreceptors and central chemoreceptors.
- Slow-wave Sleep
- Upper Airway Muscles
- Tensor Palatini
- NREM sleep
- Copyright © 2016, Journal of Applied Physiology