ABSTRACT
As can be gleaned from other chapters in this volume, the perception of an odorant depends upon the activation of a subset of -1000 olfactory receptor types distributed, in the human, across -6,000,000 receptor cells. Each receptor cell commonly carries only one type of receptor, and the relative distribution of the receptor types among the - 6,000,000 receptor cells is unknown. Since most odorous substances found in nature are comprised of more than one chemical, a typical stimulus simultaneously activates overlapping subsets or arrays of many olfactory receptor cells. From these arrays the nervous system extracts a unitary sensation for a given stimulus, although, for some substances, a few major “notes” can be discerned, as is well known to wine and beer connoisseurs. Hence, from one perspective olfaction is largely a synthetic sensory system, synthesizing a distinct individual sensory sensation from a complex set of chemicals, many of which have an individual odor. From another perspective, however, it is an analytical sensory system, capable of extracting from hundreds of potential sensations a few dominant qualities.
