Relationship between peripheral receptor code and perceived odor quality.

The discrimination of thousands of odorants is mediated by several hundred olfactory receptors (ORs). It is generally accepted that the main strategy in encoding odor quality is a combinatorial receptor code scheme, in which odorants are discriminated by different sets of ORs. In the present study, we classified 12 test odorants by their receptor codes and perceived odor qualities to examine whether odorants showing similar receptor codes are also similar in their odor qualities. Similarities of receptor codes between odorants were estimated by the overlapping responses of murine isolated olfactory sensory neurons. In contrast, we conducted a human sensory test to classify the test odorants according to their odor qualities. Despite the difference in species, the groupings of the test odorants were well conserved between receptor code and odor quality. These findings indicate that odorants that are discriminated by murine receptor codes are perceived as different odors by humans and further suggest that similarity of receptor codes correlates with that of odor quality, at least in our test odorants at the concentrations tested.