Watching the fly brain learn

The peptidergic dorsal paired medial (DPM) neurons, which innervate the mushroom bodies in Drosophila, have been widely hypothesized to be part of the unconditioned stimulus (US) pathway of odor-shock classical conditioning. In the December 2 issue of Cell, Yu et al., using functional imaging techniques, report the surprising finding that DPMs contain odor-specific memory traces and send integrated information about the conditioned stimulus (CS) to the mushroom bodies. These findings provide important new insight into the circuitry of learning in Drosophila.