Processing of pheromonal odorants has evolved in what is referred to as a labeled-line system, whereby single odorants of a given pheromonal blend bind to specific receptors as well as specific down stream processing pathways. The solution of the pheromonal odor-coding problem has evolved in response to specific evolutionary constrains of mate location and discrimination of conspecifics from those of closely related species. In the case of non-pheromonal odors, olfactory systems appear to have evolved with a small number of relatively broadly tuned receptors, as well as glomeruli, to code for a large number of ephemeral odors by processing odor information in a combinatorial manner whereby odors are assessed along a number of odor dimensions. Indeed, by their very nature, combinatorial coding schemes have a far greater capacity for odor discrimination than do labeled line schemes. However, while it is becoming increasingly clear that odor codes are distributed the specification of odor dimensionality is still poorly defined.
The specific aims of this R03 are designed to develop methods for quantifying and analyzing variation in signal processing of non-pheromonal odors that vary systematically along a restricted set of proposed odor dimensions, such as carbon chain length, and, whether experience enhances the statistical distinctiveness of these representations.
Aim 1 is designed to assess the degrees to which related odors are coded for in spatiotemporal overlapping, or combinatorial codes that vary systematically along dimensions that codify corresponding variation in the geometry of these odors. Here we will statistically model the spatiotemporal relatedness of arrays of odors that systematically vary along specified geometric dimensions. It has also been demonstrated that learning changes the odor code in some clear and reproducible ways. Yet the role these changes play are poorly understood. One likely possibility is that these changes enhance the discriminability of odors.
Aim 2 further develops Aim 1 by looking at how the relatedness of these overlapping spatiotemporal odor codes changes as moths are conditioned to related odors to food.
