Odor Mapping of the Brain Laboratory for Neuronal Recognition Molecules Laboratory for Integrative Neural Systems The sense of smell is mediated by many odor molecules inhaled in the nose. Lucretius in the ancient Greek period postulated the idea that the quality of an odor, as recognized by human beings, is closely related to the chemical structure of odor molecules. This has been gradually accepted as the chemical structures of odor molecules have been identified one by one with the progress in organic chemistry in modern times. However, it remains a mystery why the chemical structures of odor molecules are associated with our sense of smell. After exposing rats to odor molecules with various chemical structures, the Neuronal Recognition Molecules Research Team examined the spatial pattern of activated glomeruli in the olfactory bulb of the brain, using the optical measurement method. The team succeeded in generating an odor map of the olfactory bulb. In the odor map, the dorsal part of the olfactory bulb contained two domains of olfactory glomeruli, each located at a particular area and responding only to odor molecules with similar functional groups (the osmophore) and of similar quality in terms of odor. Furthermore, other characteristics of the structure of an odor molecule (such as the length or branching of carbon chains which subtly affect the quality of the odor) corresponded to the spatial arrangement of the glomeruli in each domain. Thus, it is found that an odor map of the brain detected by the optical measurement method is closely associated with the quality identification of odors as recognized by human beings. 　 Odor map of a rat olfactory bulb generated using the optical measurement method. magnified scene by clicking image Naoshige Uchida, Yuji K. Takahashi, Manabu Tanifuji, Kensaku Mori Odor maps in the mammalian olfactory bulb: domain organization and odorant structural features Nature Neuroscience, Vol.3 No.10 October 2000