Context generalization in Drosophila visual learning requires the mushroom bodies

The world is permanently changing, Laboratory experiments on learning and memory normally minimize this feature of reality, keeping all conditions except the conditioned and unconditioned stimuli as constant as possible(1). In the real world, however, animals need to extract from the universe of sensory signals the actual predictors of salient events by separating them from nonpredictive stimuli (context(2)), In principle, this can be achieved if only those sensory inputs that resemble the reinforcer in their temporal structure are taken as predictors. Here we study visual learning in the fly Drosophila melanogaster, using a flight simulator(3,4), and show that memory retrieval is, indeed, partially context-independent. Moreover, we show that the mushroom bodies, which are required for olfactory(5-7) but not visual or tactile learning(8), effectively support context generalization. In visual learning in Drosophila, it appears that a facilitating effect of context cues for memory retrieval is the default state, whereas making recall context-independent requires additional processing.