Processing of Odor Mixtures in the Mammalian Olfactory System

Animals rarely encounter odors in isolation, and their olfactory systems generally operate in the context of complex mixtures of odorants. Individual objects typically emit a multitude of volatile chemicals that become their signature for identification. In addition, chemicals emitted from multiple objects mix in the air before reaching the nose. There is great interest, therefore, in understanding how mixtures are processed by the olfactory system to allow perceiving objects and segregating them from background odors. Studies comparing the neural responses to single odorants and their mixtures show that it is often not easy to predict the mixture response from the components, suggesting that cross-odorant interactions take place at multiple levels of the mammalian olfactory system. Experiments that relate cross-odorant interactions to perception may elucidate how mixture processing underlies object identification and background segregation.