Brainstem premotor mechanisms underlying vocal production and vocal-respiratory coordination

Abstract

Speech generation critically depends on precise controls of laryngeal muscles and coordination with ongoing respiratory activity. However, the neural mechanisms governing these processes remain unknown. Here, we mapped laryngeal premotor circuitry in adult mice and viral-genetically identified excitatory vocal premotor neurons located in the retroambiguus nucleus (RAmVOC) as both necessary and sufficient for driving vocal-cord closure and eliciting mouse ultrasonic vocalizations (USVs). The duration of RAmVOC activation determines the lengths of USV syllables and post-inspiration phases. RAmVOC-neurons receive inhibitory inputs from the preBotzinger complex, and inspiration needs can override RAmVOC-mediated vocal-cord closure. Ablating inhibitory synapses in RAmVOC-neurons compromised this inspiration gating of laryngeal adduction, resulting in de-coupling of vocalization and respiration. Our study revealed the hitherto unknown circuits for vocal pattern generation and vocal-respiratory coupling. One-Sentence SummaryIdentification of RAmVOC neurons as the critical node for vocal pattern generation and vocal-respiratory coupling.