Fig. 3.

A raw figure obtained from a participant showing changes in peak genioglossus muscle activity from the initial hypoxic episode and subsequent recovery period to the final hypoxic episode and post-stimuli recovery period. Note that peak genioglossus muscle activity was greater during the last hypoxic episode compared with the initial episode and that genioglossus muscle activity during the post-stimuli recovery period was greater than measures obtained during baseline. This sustained increase in genioglossus muscle activity is referred to as long-term facilitation of upper airway muscle activity. Reprinted from “Long-term facilitation of ventilation and genioglossus muscle activity is evident in the presence of elevated levels of carbon dioxide in awake humans,” by D.P. Harris et al. Am. J. Physiol. Regul. Integr. Comp. Physiol. 291: 1111–1119, 2006.