Neural Mechanisms of Mixture Suppression in Olfaction

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Odors are complex mixtures of substances. It is difficult to predict behavioral or physiological responses to odor mixtures from the responses to the individual componentsof the mixtures. Mixtures are often significantly less stimulatory than predicted, a phenomenon called mixture suppression. This is at least partly due to poorly understood interactions that occur when multiple odorants activate the olfactory pathway simultaneously. This project addresses this problem by considering several possible mechanisms in mixture suppression: namely, mutually interfering mechanisms of transduction by the receptors and inhibitory synaptic connections in the olfactory part of the central nervous system. The research animal is the spiny lobster, in which it is known that receptor and central events both contribute to mixture suppression in olfaction. Electrophysiological methods are used to determine if different odor components activate opposing transduction processes inreceptor cells. Similar methods as well as cell staining and special techniques to localize the various substances by which nerve cells communicate with each other are used to identify inhibitory cells in the central nervous system and their connections in its olfactory areas. Mixture suppression provides a specific context in which to interpret the role of these inhibitions in recognizing odor quality. Since basic molecular and cellular processes tend to be conserved in evolution, the results can be expected to contribute to the general understanding of how complex odors are recognized in animals other than lobsters, including humans.