Brainstem circuit operations regulating the mammalian respiratory network

The core respiratory network of mammals has been investigated and modeled extensively. This accumulated work has strongly supported the current hypothesis of a network controlled by inspiratory neurons in the preBötzinger complex and motor behaviors shaped by circuits of inspiratory and expiratory neurons. We have interrogated a database of brainstem neuron spike train recordings from in vivo experiments in anesthetized or decerebrated cats from over 30 years of experiments (n=211 animals). These spike trains were obtained by simultaneous recordings with multiple tungsten electrode arrays (n=40-100 probes) that were placed in the ventrolateral respiratory column, pons, nucleus tractus solitarius (NTS), raphe nuclei and reticular formation. The database contains spike trains from over 6,700 brainstem neurons. Functional interactions between neurons were inferred from cross-correlation analysis and extracellular spike-triggered averaging. Over 160,000 cross correlations were performed of which over 9,300 functional correlations were detected. We observed: 1) cross correlations in which solely central features (consistent with parallel processes) and solely offset features (consistent with serial processes) occurred at equal frequencies; 2) direct reciprocal functional relationships with a predominance of inhibitory processes, 3) reciprocal inhibitory relationships between populations via more complex subcircuits involving at least 1 or 2 additional neurons; 4) excitatory phenomena between inspiratory and expiratory neurons that occurred sometimes as often as inhibitory phenomena, 5) high frequencies of excitation within the inspiratory neuron population as well as within the expiratory neuron population. These data support: robust excitation within the core respiratory circuit that is not well represented in current models; a high incidence of parallel circuit operations in this network; and complex circuit motifs that involve different types of respiratory neurons to achieve reciprocal functions. NIH HL 155721 and NIH HL 163008 This abstract was presented at the American Physiology Summit 2025 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.