Social attraction in Drosophila is regulated by the mushroom body and serotonergic system.

Sociality is among the most important motivators of human behaviour. However, the neural mechanisms determining levels of sociality are largely unknown, primarily due to a lack of suitable animal models. Here, we report the presence of a surprising degree of general sociality in Drosophila. A newly-developed paradigm to study social approach behaviour in flies reveal that social cues perceive through both vision and olfaction converged in a central brain region, the γ lobe of the mushroom body, which exhibite activation in response to social experience. The activity of these γ neurons control the motivational drive for social interaction. At the molecular level, the serotonergic system is critical for social affinity. These results demonstrate that Drosophila are highly sociable, providing a suitable model system for elucidating the mechanisms underlying the motivation for sociality.