BioSystems 73 (2004) 25–43 A biophysical model of vertebrate olfactory epithelium and bulb exhibiting gap junction dependent odor-evoked spatiotemporal patterns of activity Fábio M. Simões-de-Souza a,∗ , Ant ˆ onio C. Roque b a Departmento de Psicologia e Educação, Setor de Psicobiologia, Faculdade de Filosofia Ciˆ encias e Letras de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, Av. Bandeirantes 3900, 14040-901 São Paulo, Brazil b Departmento de F´ ısica e Matemática, Faculdade de Filosofia Ciˆ encias e Letras de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, São Paulo, Brazil Received 23 April 2003; received in revised form 23 April 2003; accepted 19 August 2003 Abstract This work describes a biophysical model of the initial stages of vertebrate olfactory system containing structures representing the olfactory epithelium and bulb. Its main novelty is the introduction of gap junctions connecting neurons both in the epithelium and bulb, and of biologically detailed dendrodendritic synapses between granule and mitral cells in the bulb. The model was used to simulate the effect of an odor presentation on the neural activity pattern in the epithelium and bulb. During the time for which an odor is presented with a constant concentration, there are spatiotemporal patterns in the epithelium and bulb generated by the couplings due to the gap junctions and/or dendrodendritic synapses. A study varying the strength of the gap junction coupling shows that the spatiotemporal patterns, both in the epithelium and bulb, are dependent of the coupling strength. It is also shown that the olfactory bulb’s spatiotemporal pattern depends on the existence of the dendrodendritic connections between mitral and granule cells. If these spatiotemporal patterns really exist in the early processing stages of the olfactory system they may be used for odor coding and the gap junctions and dendrodendritic synapses might have a role on it. © 2003 Elsevier Ireland Ltd. All rights reserved. Keywords: Olfactory system; Gap junctions; Dendrodendritic synapses; Spatiotemporal coding; Computational modeling 1. Introduction One of the leading hypotheses for odorant coding in the olfactory system is that identity and concentration are represented by spatiotemporal patterns of activity distributed across populations of neurons at each level of the olfactory pathway (Pearce, 1997; Èrdi et al., ∗ Corresponding author. Tel.: +55-16-6023859; fax: +55-16-6339949. E-mail address: fabioms@neuron.ffclrp.usp.br (F.M. Simões-de-Souza). 1998; White and Kauer, 1999, 2001; Friedrich and Stopfer, 2001; Laurent et al., 2001; Friedrich, 2002; Spors and Grinvald, 2002). In order to verify this hy- pothesis, in parallel with the development and/or im- provement of experimental techniques to register and analyze simultaneously the activity of large neural populations throughout the olfactory system, it also is important to construct large-scale computational models of the olfactory system that can generate spa- tiotemporal activity patterns to be used as tools for investigating possible coding schemes supported by them. 0303-2647/$ – see front matter © 2003 Elsevier Ireland Ltd. All rights reserved. doi:10.1016/j.biosystems.2003.08.002