A model for temporal and intensity coding in insect olfaction by a network of inhibitory neurons

Female insects release sex-pheromones which attract their conspecific males. These pheromones are detected through a distinct male-specific olfactory subsystem which resides at the first stage of olfactory processing, and consists of receptor, local and projection (relay) neurons. When male insects were stimulated by female sex-pheromones, some projection neurons could distinguish between different pheromones, following input and code stimulus intensity. Presented here, is a simple biophysical model that described characteristic bursting responses observed for projection neurons. The bursting behavior of the model resulted from a particular cellular mechanism and specific network architecture. At the neuron level, a rapidly activating and slowly inactivating low-threshold calcium channel provided depolarizing current for bursting, while at the network level, inhibitory neurons implementing dis-inhibition which triggered this calcium channel. Also, the network architecture provided a mechanism by which certain projection neurons coded temporal input and stimulus intensity.