Common drive in hypoglossal and trigeminal motor neurons

Simultaneous genioglossus (GG) and tensor palatini (TP) electromyogram (EMG) recordings in a 52-year-old male with obstructive sleep apnea (apnea–hypopnea index547/h), shortly after increasing continuous positive airway pressure (CPAP) to 10 cm H2O. Single motor units (SMUs) were recorded on both EMG channels and were sorted according to their unique profiles (shown at top of Figure 1). Two individual SMUs were identified on the GG-EMG (Channel 24:blue and red units) with instantaneous frequencies shown on 24a and 24d, respectively. A single SMU was identified on the TP-EMG (Channel 19:red unit). The instantaneous frequency of the TP unit (19b) nearly exactly matches that of the Red GG unit (24d), withr250.99 and both units stop firing at 30s (presumably due to reduced respiratory drive following the CPAP increase). This suggests that some respiratory pattern–generating neurons simultaneously output to trigeminal and hypoglossal motor neurons, causing synchronous firing of some motor units (common motor drive) in the different muscles.