One of the most pressing issues in understanding the sense of smell is to understand the mechanisms that carry coded information from the nose into the brain. The peripheral nerve cells, or neurons, form functional contacts called synapses with central neurons. The first synaptic relay occurs in anatomical clusters of cells called glomeruli, sharing this fundamental organization across a wide phylogenetic range animals from lobsters, insects, snails, fish and humans. These cell clusters of olfactory glomeruli, like the neural cartridges in vision and cortical barrels in touch, are thought to play an important role in stimulus recognition, but their role in central olfactory recognition remains unknown. This project uses physiological, pharmacological and immunocytochemical techniques on the distinct morphological regions within the glomeruli in the lobster as a model system. Results will define the odor selectivity of glomeruli, and determine the extent to which regional post-convergent processing within and among glomeruli can shape the odor selectivity of a glomerulus. This study will give new insight into neural integration of olfaction at the crucial first stage of central processing, and will have an impact beyond simply chemosensory neuroscience to brain function in general, to modeling of neural networks, and to understanding how recognition of environmental stimuli is integrated into behavior.