Brainstem control of vocalization and its coordination with respiration

Abstract

Phonation critically depends on precise controls of laryngeal muscles in coordination with ongoing respiration. However, the neural mechanisms governing these processes remain unclear. We identified excitatory vocalization-specific laryngeal premotor neurons located in the retroambiguus nucleus (RAmVOC) in adult mice as both necessary and sufficient for driving vocal cord closure and eliciting mouse ultrasonic vocalizations (USVs). The duration of RAmVOC activation can determine the lengths of both USV syllables and concurrent expiration periods, with the impact of RAmVOC-activation depending on respiration phases. RAmVOC-neurons receive inhibition from the preBötzinger complex, and inspiration-needs override RAmVOC-mediated vocal-cord closure. Ablating inhibitory synapses in RAmVOC-neurons compromised this inspiration gating of laryngeal adduction, resulting in discoordination of vocalization with respiration. Our study revealed the circuits for vocal production and vocal-respiratory coordination.