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Biological Cybernetics

, Volume 87, Issue 3, pp 220–229 | Cite as

Functionality of divergence and convergence in a model of the insect olfactory system

  • Rémy Lestienne
  • Brigitte Quenet
  • Sébastien Bouret
  • Olivier Parodi

Abstract.

Recent studies have shown that the insect olfactory system uses a spatio-temporal encoding of odours in the population of projection neurons in the antennal lobe, and suggest that the information thus coded is spread across a large population of Kenyon cells in the mushroom bodies. At this stage, the temporal part of the code might be transformed into a spatial code, especially via the temporally sensitive mechanisms of paired–pulse facilitation and feedback inhibition with its possible associated rebound. We explore here a simple model of the olfactory system using a three–layer network of formal neurons, comprising a fixed number (three) of projection and inhibitory neurons, but a variable number of Kenyon cells. We show how enlarging the divergence of the network (i.e. the ratio between the number of Kenyon cells to the number of input – projection – neurons) alters the number of different output spatial states in response to a fixed set of spatio-temporal inputs, and may therefore improve its effectiveness in discriminating between these inputs. Such enlarged divergence also reduces the variation of this effectiveness among random realisations of the network connectivity. Our model shows that the discriminative effectiveness first increases with the divergence, and then plateaus for a divergence factor of ∼20. The maximal average number of different outputs was 470.2, which was computed from some simulations with random realisations of connectivity and with a set of 512 possible inputs. The discriminative effectiveness of the network is sensitive to paired-pulse facilitation, and especially to inhibition with rebound.

Keywords

Odour Projection Neuron Olfactory System Spatial State Temporal Part 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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Copyright information

© Springer-Verlag Berlin Heidelberg 2002

Authors and Affiliations

  • Rémy Lestienne
    • 1
  • Brigitte Quenet
    • 2
  • Sébastien Bouret
    • 1
  • Olivier Parodi
    • 2
  1. 1.Neuromodulation et Processus Mnésiques, Lab. Neurobiologie des Processus Adaptatifs, Université P. et M. Curie, 9 Quai St Bernard, 75005 Paris, FranceFR
  2. 2.Laboratoire d'Electronique-ESPCI, Ecole Supérieure de Physique et Chimie Industrielles de la Ville de Paris, 10 rue Vauquelin, 75005 Paris, FranceFR

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