Brainstem control of vocalization and its coordination with respiration

Phonation critically depends on precise controls of laryngeal muscles in
coordination with ongoing respiration. However, the neural circuit
mechanisms governing these processes remain unclear. Here, 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 hitherto unknown circuits for vocal
production and vocal-respiratory coordination.