Starvation promotes odor/feeding-time associations in flies.

Starvation causes a motivational state that facilitates diverse behaviors such as feeding, walking, and search. Starved Drosophila can form odor/feeding-time associations but the role of starvation in encoding of "time" is poorly understood. Here we show that the extent of starvation is correlated with the fly's ability to establish odor/feeding-time memories. Prolonged starvation promotes odor/feeding-time associations after just a single cycle of reciprocal training. We also show that starvation is required for acquisition but is dispensable for retrieval of odor/feeding-time memory. Finally, even with extended starvation, a functional circadian oscillator is indispensable for establishing odor/feeding-time memories.

cAMP signaling mediates behavioral flexibility and consolidation of social status in Drosophila aggression.

Social rituals, such as male-male aggression in Drosophila, are often stereotyped and the component behavioral patterns modular. The likelihood of transition from one behavioral pattern to another is malleable by experience and confers flexibility to the behavioral repertoire. Experience-dependent modification of innate aggressive behavior in flies alters fighting strategies during fights and establishes dominant-subordinate relationships. Dominance hierarchies resulting from agonistic encounters are consolidated to longer-lasting, social-status-dependent behavioral modifications, resulting in a robust loser effect. We showed that cAMP dynamics regulated by the calcium-calmodulin-dependent adenylyl cyclase, Rut, and the cAMP phosphodiesterase, Dnc, but not the Amn gene product, in specific neuronal groups of the mushroom body and central complex, mediate behavioral plasticity necessary to establish dominant-subordinate relationships. rut and dnc mutant flies were unable to alter fighting strategies and establish dominance relationships during agonistic interactions. This real-time flexibility during a fight was independent of changes in aggression levels. Longer-term consolidation of social status in the form of a loser effect, however, required additional Amn-dependent inputs to cAMP signaling and involved a circuit-level association between the α/ß and γ neurons of the mushroom body. Our findings implicate cAMP signaling in mediating the plasticity of behavioral patterns in aggressive behavior and in the generation of a temporally stable memory trace that manifests as a loser effect.