An important sensory appendage for insects is the flagellum of the antenna, containing thousands of receptors called sensilla that have been classified into types, including some specialized for chemosensory functions. The nerve from the flagellum contains many nerve fibers, or axons, which form particular groupings when they enter the brain and terminate in distinctive structures called glomeruli. Each glomerulus is a sphere-like complex in which nerve cells make functional contacts called synapses, where interactions occur between incoming and outgoing information, modulated by local nerve cells. The glomerular structure in insects has several similarities to the glomerulus also found in the vertebrate olfactory bulb, and it is believed that this structure forms an information processing module for synaptic interactions. This work will focus on how olfactory information is mapped in the glomeruli, to see whether in insects olfactory receptors are represented in different glomeruli according to their functional tuning, their antennal location, or both. Light microscopy and electron microscopy will be used to clarify the architecture underlying the connections between neurons that provide input and output, and the convergence and local circuits that process olfactory information. The insect system offers an advantageous model because it is possible find uniquely identifiable single neurons in the brain. Results from this work will be valuable to understanding information processing in general, to chemosensory neuroscience in the vertebrates as well as invertebrates, to studies on insects as model systems during neural development of highly specific neural connections, and to agriculturally related studies of insect feeding or reproduction which have chemosensory components.
