The multifunctionality of the brainstem breathing control circuit

Subconscious breathing is generated by a network of brainstem nodes with varying purposes, like pacing breathing or patterning a certain breath phase. Decades of anatomy, pharmacology, and physiology studies have identified and characterized the system’s fundamental properties that produce robust breathing, and we now have well-conceived computational models of breathing that are based on the detailed descriptions of neuronal connectivity, biophysical properties, and functions in breathing. In total, we have a considerable understanding of the brainstem breathing control circuit. But, in the last five years, the utilization of molecular and genetic approaches to study the neural subtypes within each node has led to a new era of breathing control circuit research that explains how breathing is integrated with more complex behaviors like speaking and running and how breathing is connected with other physiological systems and our state-of-mind. This review will describe the basic role of the key components of the brainstem breathing control circuit and then will highlight the new transformative discoveries that broaden our understanding of these breathing control brain areas. These new studies serve to illustrate the creativity and exciting future of breathing control research. The following are the recently identified properties of the breathing control circuit. • The breathing pacemaker is used to form complex sounds during vocalization. • The primary chemosensor is repurposed to stimulate breathing during locomotion. • The parabrachial nucleus forms a hub to connect breathing and emotion. • The nucleus tractus solitarius coordinates breathing and metabolism.