Animals monitor the density of conspecifics in their environment and regulate their drive to seek social interaction accordingly. Prolonged isolation increases this drive, which is alleviated upon reintroduction into a social context — but how such experience is converted into a persistent neural state remains unclear. Here we show that prior social environment alters the activity state of a dopaminergic circuit that causally modulates social drive in Drosophila. Using a battery of behavioral assays, we found that socially isolated males vigorously track a moving visual target, whereas males previously housed with females suppress tracking even under identical, optogenetically induced social arousal. These distinct behavioral states are dictated by PAM-γ4 dopamine neurons, whose movement sensitivity switches with social environment. In isolated males, these neurons are selectively inhibited during movement, permitting tracking, whereas prior female experience dampens this inhibition. The effects of female experience are mediated by contact-dependent pheromones, which evoke calcium and cAMP signaling in PAM-γ4, suggesting a pathway by which discrete contact events are converted into a lasting neural state. Finally, suppression is induced by conspecific females but not by females of cohabiting sibling species, affording an estimate of conspecific density in the environment. Together, these results reveal how discrete social encounters are converted into a persistent behavioral state.

 

東京大学大学院理学系研究科・生物科学専攻・脳機能学研究室