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 sexpheromones, 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.