BEHAVIORAL AND PHYSIOLOGICAL MECHANISMS OF OLFACTION

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The honey bee (Apis mellifera) will be used to study behavioral and physiological mechanisms involved in generating neural representations in the olfactory system. The olfactory systems of both vertebrates and invertebrates, such as the honey bee, are structured like distributed processors. Anatomical features of these systems resemble features of neural network models of pattern recognition and memory, which compute input/output relationships as a function of intermediate levels of processing among elements that have been activated in parallel. Recent models of olfactory systems have identified temporal fluctuation in the odor signal, pattern recognition, and associative memory as potentially important features that are extracted by early olfactory processing. Therefore, because of the anatomical similarities between vertebrates and invertebrates, use of an invertebrate animal as a model system will provide generalizable insights into how neural representations in the olfactory systems of a wide variety of animals are generated. Honey bees are ideally suited for the combination of behavioral, pharmacological, and physiological studies proposed. Workers learn to respond to floral odorants and pheromones in novels ways. Therefore, mechanisms proposed for pheromone processing in insects can be tested for applicability to floral odorant processing. Behavioral experiments will involve conditioning worker bees to respond to an odorant or to mixtures of two or more odorants. Subsequent test will be designed to evaluate mechanisms that explain the following processes: (1) why one odorant overshadows or fails to overshadow another; (2) interaction of neural representations for odorants and tastes; (3) how one odorant can block learning about a second after the first has been associated with a reinforcer such as sucrose. Pharmacological experiments are proposed to study the role of olfactory lobe inhibitory processing in generating mixture and temporal processing phenomena. Several different GABA agonists and antagonists will be evaluated, including those that interact with GABA-associated benzodiazepine binding sites.