Motor unit activity in upper airway muscles genioglossus and tensor palatini

• Genioglossus and tensor palatini motoneurons have relatively high common drive.
• Common drive is stronger between inspiratory modulated than tonic motoneurons.
• Inspiratory modulated but not tonic motoneurons share common drive across muscles.
• Common drive is stronger for unilaterally than bilaterally located motoneurons.
• The functional role of inspiratory motoneurons differs from tonic motoneurons.

Common oscillatory inputs to genioglossus (GG) and tensor palatini (TP) motoneurons were assessed using coherence analysis. Oscillations in the ranges 0–5 Hz (common drive) and 10–30 Hz (short term synchrony) were analyzed. GG and TP electromyograms were recorded via intramuscular fine wire electrodes in 32 subjects during wakefulness. Coherence analysis was conducted on 201 pairs of motor units paired according to their discharge patterns. Results were similar for the two muscles. Common drive was significantly higher for unilateral than bilateral pairs of units (p < .001), and was highest in Inspiratory Tonic pairs and lowest in Tonic pairs (p < .001). Pairs constructed from one muscle had higher common drive than pairs from two muscles (p < .001), the difference being greater for tonic pairs (interaction effect, p = .003). Short term synchrony was weak. The results indicate strong common drive to GG and TP phasic motoneurons, while common drive to Tonic motoneurons was weaker and idiosyncratic to each muscle.