Our research is primarily concerned with olfaction, or the sense of smell. For most animals, smell is the primal sense, one they rely on to identify food, predators and mates. For us, the olfactory system provides an excellent system with which to address basic issues of neuroscience such as the nature of sensory representations and their influence on behavior using all of the tools that modern biology provides. Our current experiments are carried out in two model species, the mouse and fruit fly.
In the mouse, olfactory perception is initiated by the recognition of odors by a large repertoire of receptors in the sensory epithelium of the nose. Distributed neural activity across these cells resulting from odor stimulation is transformed at the next stage of processing, the olfactory bulb. This transformation results from the convergence of like axons of sensory neurons, each bearing the same receptor, to distinct structures in the bulb called glomeruli. Glomeruli responding to many odor classes are segregated into a coarse chemotopic map. We have recently performed in vivo optical imaging of responses at the next stage of olfactory processing, the piriform cortex, using a calcium-sensitive dye and two-photon microscopy. These experiments have revealed a second transformation in which odors activate a subpopulation of neurons distributed across the piriform cortex with no evidence of chemotopy. The piriform therefore discards spatial segregation as well as chemotopy and returns to a highly dispersed organization in which different odors activate unique ensembles of cortical neurons.