Respiratory neuronal assemblies

This review describes results from in vivo experiments on brain stem networ k mechanisms that control breathing. Multi-array recording technology and c omputational methods were used to test predictions derived from simulations of respiratory network models. This highly efficient approach has the adva ntage that many simultaneously recorded neurons are subject to shared stimu lus, history, and state-dependent conditions. Our results have provided evi dence for concurrent or parallel network interactions in the generation and modulation of the respiratory motor pattern. Recent data suggest that baro receptors, chemoreceptors, nociceptors, and airway cough receptors shape th e respiratory motor pattern, at least in part, through a system of shared c oordinated 'multifunctional' neurons distributed in the brain stem. The 'gr avity method' for the analysis and representation of multi-neuron data has demonstrated respiratory phase-dependent impulse synchrony among neurons wi th no respiratory modulation of their individual firing rates. The detectio n of this emergent property motivated the development of pattern detection methods that subsequently identified repeated transient configurations of t hese 'correlational assemblies'. These results support the view that inform ation can be 'coded' in the nervous system by spike timing relationships, i n addition to firing rate changes that traditionally have been measured by neurophysiologists. (C) 2000 Elsevier Science B.V. All rights reserved.