におい知覚のロジックを探る

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Exploring the Logic for Olfactory Perception Mori, Kensaku (Dept. Physiol., Grad. Sch. Med. Univ. of Tokyo, Japan) The olfactory perception plays a key role in the daily life of human and animals. Since the discovery of odorant receptors in 1991, we have witnessed a rapid progress in the understanding of the olfactory system. However, the recent studies focused on the early olfactory processing at the levels of odorant receptors, sensory neurons and olfactory bulb (OB). The central processing of olfactory information in the mammalian brain is still not well understood. Late Professor Sadayuki Takagi and his colleagues are the pioneers who explored the odorant-response specificity of neurons from the OB through the olfactory cortex to the orbitofrontal cortex in the monkey brain. In the OB, individual glomeruli represent a single odorant receptor, and the glomerular sheet of the OB forms odorant receptor maps. Studies of OB mapping show that (1) individual glomeruli respond to a range of odorants that share a specific combination of molecular-features, that (2) each glomerulus appears to be unique in its molecular receptive range property, and that (3) glomeruli with similar molecular receptive range properties are located in proximity and form molecular-feature clusters. The olfactory cortex reads the molecular-feature maps in the OB and is thought to integrate information from different molecular-feature detecting glomeruli to form the olfactory image of objects. We discuss also behavioral-state-dependent gating of olfactory information flow at the level of the olfactory cortex. [J Physiol Sci. 2006;56 Suppl:S4]