Neurons within the pre-Bötzinger complex of the ventral respiratory group (VRG) in the medulla generate rhythmic network activity which has been shown to be essential for normal breathing in vivo. Furthermore, many physiological responses of this network are preserved in transverse medullary brain slice preparations, where bursts of population discharge are typically recorded with large, low-impedance electrodes . Recent analysis of multiunit extracellular recordings from this in vitro preparation has shown that the onset timing of spikes from the individual neurons that make up this rhythm is quite variable on a burst-by-burst basis. A conductance-based model  of this network with all-to-all connectivity fails to reproduce this variability, while a model with sparse (but proportionally stronger) synaptic coupling generates firing patterns with a higher fidelity to the experimental results (see Figure 1). Specifically, the mean variance of burst-triggered spike timing was 0.0218 ± 0.0184 (SD) for in vitro recordings, 0.0347 ± 0.0267 for sparsely connected network models, and 0.0004 ± 0.0023 for fully connected models. Continuing simulations will explore further relationships between parameters of network topology and spike timing variability.
Committee on Computational Neuroscience, The University of Chicago
Department of Organismal Biology and Anatomy, The University of Chicago
Ramirez J-M, Tryba AK, Peña F: Respiratory rhythm generation: converging concepts from in vitro and in vivo approaches?. Respir Physiol Neurobiol. 2002, 131 (1–2): 43-56. 10.1016/S1569-9048(02)00036-8.View ArticlePubMedGoogle Scholar
Rybak IA, Shevtsova NA, Ptak K, McCrimmon DR: Intrinsic bursting activity in the pre-Botzinger complex: role of persistent sodium and potassium currents. Biol Cybern. 2004, 90 (1): 59-74. 10.1007/s00422-003-0447-1.View ArticlePubMedGoogle Scholar