[A network capable of reading the temporal codes in the olfactory discrimination of insects]

Recent work on the insect olfactory system has shown that its mushroom bodies (one of its major components) are involved in the fine discrimination of odours and that the temporal organisation of spike discharges plays a fundamental role. We propose here a model of a network that is able to decode the temporal patterns which characterise an odour. This model has three fundamental properties that seem to exist in all mushroom bodies of insects studied so far: a) long lasting inhibitions with rebounds, able to facilitate delayed spike generation; b) synaptic plasticity, which allows the network to learn to recognise temporal patterns; c) above all a large interconnection, which allows this network to recognise intervals of various duration. This model thus appears suited to identify combinations of temporal patterns in the dendrites of Kenyon cells (the principal cells in the calyces of the mushroom bodies). Moreover, the mushroom bodies integrate multimodal inputs, suggesting that the detection of temporal patterns may be extended to the detection of a complex environment, combining in particular olfactive and visual inputs.