3. Mainolfactorylearningandmemory
3.1. Non-socialodourlearninginthemainolfactorysystem
OSNs in the main olfactory epithelium express only one olfac- tory receptor type. The mouse olfactory bulb contains roughly 2000 glomeruli, each glomerulus receiving projections from OSNs expressing the same receptor type, with approximately 2 glomeruli for each receptor type in each olfactory bulb (Mombaerts et al., 1996). The olfactory receptor type expressed by the neuron deter- mines the location of its glomerular convergence on the MOB. This self-organising developmental process leads to a spatial mapping of input from different receptor types (Imai et al., 2006), which is broadly consistent within and between individual mice and rats (Soucy et al., 2009). There appears to be some aspect of localisation of responses to different odourant classes across broad regions of the MOB (Mori and Sakano, 2011). However, no topographic map- ping has been found at a finer scale, in that neighbouring glomeruli have been found to respond to completely different odourant types (Soucy et al., 2009). Each olfactory receptor type responds .