Enantioselectivity of odor perception in squirrel monkeys and humans

With use of a conditioning paradigm, the ability of six squirrel monkeys to distinguish between 10 pairs of enantiomers, i.e., odorants that are ident ical except for chirality, was investigated. As a group, the animals were o nly able to discriminate between the optical isomers of alpha-pinene, carvo ne, limonene, and fenchone, whereas they failed to distinguish between the (+) and (-) forms of beta-citronellol, menthol, rose oxide, 2-butanol, a-te rpineol, and camphor. With use of a triple forced-choice procedure, 10 huma n subjects were tested for their ability to discriminate between the same e nantiomeric odor pairs in parallel and, with the exception of fenchone, sho wed a very similar pattern of performance compared with the squirrel monkey s. These findings support the assumption that human and nonhuman primates m ay share common principles of odor quality perception. Furthermore, the res ults suggest that, in both species, enantioselective molecular odor recepto rs may only exist for some, but not all volatile enantiomers and thus that chiral recognition of odorants is not a general phenomenon, but may be rest ricted to some substances.