In mammals, discrete brain regions mediate the conditioned response to drug reward including the nucleus accumbens, prefrontal cortex, amygdala, and dorsal striatum1. In Drosophila, the regions of the brain mediating ethanol preference or reward are unknown. However, it is well established that discrete subsets of neurons within the fly mushroom body play a role in odor memory processing, including the conditioned response to sugar reward21. In addition, dopaminergic neurons known to play a role in modulating memories for sucrose reward project to the mushroom body22. Since the mushroom body is important for memories of sugar reward, and dopamine is required for expression of memories of ethanol reward, we hypothesized that the mushroom body may be required for conditioned preference.
