Taste representations in the Drosophila brain.

Drosophila taste compounds with gustatory neurons on many parts of the body, suggesting that a fly detects both the location and quality of a food source. For example, activation of taste neurons on the legs causes proboscis extension or retraction, whereas activation of proboscis taste neurons causes food ingestion or rejection. We examined whether the features of taste location and taste quality are mapped in the fly brain using molecular, genetic, and behavioral approaches. We find that projections are segregated by the category of tastes that they recognize: neurons that recognize sugars project to a region different from those recognizing noxious substances. Transgenic axon labeling experiments also demonstrate that gustatory projections are segregated based on their location in the periphery. These studies reveal the gustatory map in the first relay of the fly brain and demonstrate that taste quality and position are represented in anatomical projection patterns.