A perfumer's ability to make fine distinctions among similar odors and to identify individual chemical components in a mixture is recognized as more art than science. This is true because the manner in which the olfactory system works is complex and at times baflling to scientists, Some knowledge is available about the anatomy and neurophysiology of the olfactory system and about the physical and chemical properties of the odorants. However, neither the initiaI step of interaction between the odorant and the receptor, nor the nature of the receptor, nor the process of olfactory coding within the brain is well understood.
To be perceived as an odorant, a molecule must be volatilized from its source, inhaled into the nasal cavity and dissoIved in the protective mucus layer lining the epitheliums which contains the olfactory sensory cells. It is believed that the molecule then must be bound by a protein receptor on hair-like protrusions (cilia) from the cell. The presumed binding process results in dramatic changes within the cell initiating olfactory nerve impulses which travel from the sensory cell to the olfactory lobe of the brain. Finally, in what is probably an extremely complex process, the brain interprets the incoming signals by associating them with a previous olfactory experience in order to assign an odor descriptor. The phenomenon of odorant-receptor binding the type of neurotransmitters involved in nerve-lobe communicating, and the correlation between odor quality and regional neural activity within the olfactory lobe and other parts of the brain are all active areas of research.
