Reward re-exposure driven memory re-evaluation in Drosophila melanogaster

In a changing world, re-evaluating learned information allows animals and humans to correct inadequate memories. However, the neuronal principles that govern these memory update processes are little understood. Here we show that manipulating dopamine neurons can bidirectionally change reward-reinforced olfactory memories in Drosophila melanogaster. Our data suggest a relationship between pathways involved in memory acquisition and those necessary for changing memory accessibility. Unpaired reward re-exposure that activates dopamine neurons also leads to memory devaluation. However, our data demonstrate that these two phenomena are controlled differently and recruit separate neuronal pathways. In contrast to dopamine driven memory update, sugar-reward-mediated memory devaluation is not only dopamine-independent but also controlled by context. Together our data show that memories are not static and can be updated by multiple pathways. Our findings can provide valuable insights for future investigations in the context of update related strategies to target maladaptive forms of reward memories.