Fig. 1.

Schematic of the timeline for the experimental protocol. Pulses: brief pulses of negative upper-airway pressure were delivered to elicit upper airway reflex responses and respiratory-related evoked potential waveforms. Iron Lung: entrained iron lung ventilation was performed to examine the response of the genioglossus muscle to negative upper-airway pressure and any potential differences in responsiveness in the evening (PM) compared with the morning (AM). 8 h standard PSG: polysomnography was performed to document the presence or absence of sleep-disordered breathing (the epiglottic pressure catheter was removed). Force/Task Failure: maximal tongue protrusion force and time to task failure protocols were performed. Refer to the text for further details.