Sequential learning of pheromonal cues modulates memory consolidation in trainer-specific associative courtship conditioning

Abstract

Background: Associative memory formation requires that animals choose predictors for experiences they need to remember. When an artificial odor is paired with an aversive experience, that odor becomes the predictor. In more natural settings, however, animals can have multiple salient experiences that need to be remembered and prioritized. The mechanisms by which animals deal with multiple experiences are incompletely understood. Results: Here we show that Drosophila males can be trained to discriminate between different types of female pheromones; they suppress courtship specifically to the type of female that was associated with unsuccessful courtship. Such "trainer- specific" learning is mediated by hydrocarbon olfactory cues and modifies the male's processing of those cues. Animals that are unable to use olfactory cues can still learn by using other sensory modalities, but memory in this case is not specific to the trainer female's maturation state. Concurrent and serial presentation of different pheromones demonstrates that the ability to consolidate memory of pheromonal cues can be modified by the temporal order in which they appear. Conclusion: Suppression of memory by new learning demonstrates that the dynamics of memory consolidation are subject to plasticity in Drosophila. This type of metaplasticity is essential for navigation of experience-rich natural environments.