Courtship behavior induced by appetitive olfactory memory.

Reinforcement signals such as food reward and noxious punishment can change diverse behaviors. This holds true in fruit flies, Drosophila melanogaster, which can be conditioned by an odor and sugar reward or electric shock punishment. Despite a wide variety of behavior modulated by learning, conditioned responses have been traditionally measured by altered odor preference in a choice, and other memory-guided behaviors have been only scarcely investigated. Here, we analyzed detailed conditioned odor responses of flies after sugar associative learning by employing a video recording and semi-automated processing pipeline. Trajectory analyses revealed that multiple behavioral components were altered along with conditioned approach to the rewarded odor. Notably, we found that lateral wing extension, a hallmark of courtship behavior of D. melanogaster, was robustly increased specifically in the presence of the rewarded odor. Strikingly, genetic disruption of the mushroom body output did not impair conditioned courtship increase, while markedly weakening conditioned odor approach. Our results highlight the complexity of conditioned responses and their distinct regulatory mechanisms that may underlie coordinated yet complex memory-guided behaviors in flies.