Neurons expressing the same receptor genes within each zone appear to be randomly arranged. In the olfactory bulb, however, fibers from neurons with the same receptor converge on just one or a few glomeruli. Research suggests that an individual odor molecule stimulates several types of receptors, each of which responds to a part of the molecule's structure. Brain mapping techniques have shown that the pattern of glomeruli activated by each odor forms a map or code that the brain may recognize as a unique scent. Recently, researchers identified a surprisingly large family of genes in rats that appears to code for odor receptors.
Olfactory receptors are very specific.
This is a schematic view of olfactory epithelial neurons and their projection to the olfactory bulb in the brain. The receptors activate one or very few transduction cascades. Each receptor type may recognize many odorants, and vice versa, so odor quality is probably perceived through a pattern of cell activities. The reception and the encoding stage of taste information is very similar to that of olfaction. The nose knows by Dr. Chudler, Univ. of Washington.