Email updates

Keep up to date with the latest news and content from BMC Neuroscience and BioMed Central.

This article is part of the supplement: Nineteenth Annual Computational Neuroscience Meeting: CNS*2010

Open Access Poster Presentation

Network model for visually mediated ciliary locomotion in Hermissenda

Douglas A Baxter* and Terry Crow

Author Affiliations

Department of Neurobiology and Anatomy, The University of Texas Medical School at Houston, Houston, TX 77030, USA

For all author emails, please log on.

BMC Neuroscience 2010, 11(Suppl 1):P59  doi:10.1186/1471-2202-11-S1-P59

The electronic version of this article is the complete one and can be found online at: http://www.biomedcentral.com/1471-2202/11/S1/P59


Published:20 July 2010

© 2010 Baxter and Crow; licensee BioMed Central Ltd.

Poster Presentation

The overall goal of this study is to investigate the ways in which learning modifies behavior. A combination of computational and empirical studies is being used to address this issue. Empirical studies investigate learning from a cellular and synaptic perspective in the relatively simple nervous system of the nudibranch mollusk Hermissenda [1-3]. Pavlovian conditioning produces light-elicited inhibition of normal positive phototaxis in Hermissenda. Learning changes both cellular excitability and synaptic strength in the neural circuit that supports phototaxis. In the present study, a model of the circuit that supports visually mediated locomotion (Fig. 1A) was developed. Consistent with empirical observations, simulated responses to light increased the level of VP1 spike activity (Fig. 1B1), which is equivalent to positive phototaxis. Simulations indicated that phototaxis resulted from disinhibition of VP1. Light increased activity in Ie and decreased activity in Ii (Fig. 1B2). The net result was less activity in IIIi and disinhibition of VP1 (Fig. 1B2). Simulations also indicated that disinhibition produced phototaxis only if VP1 had a high level of tonic firing. The model is being refined and expanded, and will be used to investigate the generation of other behaviors (e.g., foot contraction), the responses to other sensory inputs (e.g., gravity), and the influence of learning-induced plasticity (e.g., increased Ie excitability and decreased VP1 tonic firing). Simulations also will help identify features of the model that warrant further empirical investigation.

thumbnailFigure 1. Network model for visually mediated ciliary locomotion. A: The model had six cells: LB, lateral B-type photoreceptor; Ib, Ie, Ii and IIIi, interneurons; VP1, ciliary motor neuron. The cells were Hodgkin-Huxley-like neurons. Membrane conductances also included noise. The match between empirical data and model properties was qualitative. For example, all synaptic connections were modeled as monosynaptic, which reflected ‘functional’ connections. The circuit was implemented in SNNAP [4]. B1: The model responded to light, which was simulated by depolarizing LB, with increased VP1 activity. B2: The mean (+/- SD; n = 7) spiking frequency (Hz) of each cell before (dark) and during the light stimulus (light). Noise produced variability among simulations. In some cases, the error bars were not visible.

Acknowledgements

This work was supported by NIH grants P01 NS038310 and R01 MH058698.

References

  1. Crow T: Pavlovian conditioning of Hermissenda: Current cellular, molecular, and circuit perspectives.

    Learn Mem 2004, 11:229-238. PubMed Abstract | Publisher Full Text OpenURL

  2. Crow T, Tian L-M: Pavlovian conditioning in Hermissenda: A circuit analysis.

    Biol Bull 2006, 210:289-297. PubMed Abstract | Publisher Full Text OpenURL

  3. Crow T, Tian L-M: Neural correlates of Pavlovian conditioning in components of the neural network supporting ciliary locomotion in Hermissenda.

    Learn Mem 2003, 10:209-216. PubMed Abstract | Publisher Full Text | PubMed Central Full Text OpenURL

  4. Baxter DA, Byrne JH: Simulator for neural networks and action potentials.

    Methods Mol Biol 2007, 401(z):127-154.

    (SNNAP is available at http://www.snnap.uth.tmc.edu webcite)

    PubMed Abstract OpenURL