Large scale neural dynamics of breathing in‐vivo and in‐vitro

Abstract

The neural control of breathing involves the coordinated activity of populations of medullary neurons distributed along the rostrocaudal aspect of the ventrolateral medulla: the so called Ventral Respiratory Group (VRG). The VRG consists of genetically diverse and anatomically distributed populations of neurons that form interconnected microcircuits necessary for the maintenance of the respiratory rhythm and the recruitment of respiratory muscles. Additionally, the VRG is subject to modulation from extra-medullary centers as well as feedback from ascending afferents. Together, the VRG is capable of robust, yet labile, generation of respiration. This generation arises from the dynamic coordination of VRG neurons, but how the activity of these neurons is coordinated across the VRG in-vivo remains poorly understood. Here, we use cutting edge electrophysiological recording techniques (Neuropixels) to record simultaneously from hundreds of neurons across the VRG in anesthetized mice and horizontal slices in vitro. We couple this with an optogenetic tagging approach to determine the genetic identity of a subset of the recorded neurons. We find inspiratory and expiratory related neurons distributed throughout the VRG, with higher proportions of expiratory neurons than expected from in-vitro studies. Moreover, correlated activity across simultaneously recorded neurons uncovers dynamically coordinated ensembles of neurons that define “cell assemblies”. These cell assemblies give rise to discretely different patterns of respiratory activity, including specific, distributed populations recruited during hypoxia induced gasping. Together, these data provide an integrated view of the dynamic coordination of neural activity driving breathing in the intact animal.