A dimorphic pheromone circuit in Drosophila from sensory input to descending output

Male-versus-female response to a pheromone Innate differences between male and female behaviours must be inscribed in their respective genomes, but how these encode distinct neuronal circuits remains largely unknown. Focusing on sex-specific responses to the cVA pheromone in fruitflies, Richard Axel and colleagues have now identified a chain of four successive neurons carrying olfactory signals down to motor centres, with all male-to-female anatomical differences lying downstream of a conserved sensory cell. The techniques developed by the team should help others in the task of neuronal circuit mapping, which remains daunting even for the relatively simple fly brain.