A permissive role of mushroom body α/β core neurons in long-term memory consolidation in Drosophila

Background: Memories are not created equally strong or persistent for different experiences. In Drosophila, induction of long-term memory (LTM) for aversive olfactory conditioning requires ten spaced repetitive training trials, whereas a single trial is sufficient for LTM generation in appetitive olfactory conditioning. Although, with the ease of genetic manipulation, many genes and brain structures have been related to LTM formation, it is still an important task to identify new components and reveal the mechanisms underlying LTM regulation. Results: Here we show that single-trial induction of LTM can also be achieved for aversive olfactory conditioning through inhibition of highwire (hiw)-encoded E3 ubiquitin ligase activity or activation of its targeted proteins in a cluster of neurons, localized within the α/β core region of the mushroom body. Moreover, the synaptic output of these neurons is critical within a limited posttraining interval for permitting consolidation of both aversive and appetitive LTM. Conclusions: We propose that these α/β core neurons serve as a "gate" to keep LTM from being formed, whereas any experience capable of "opening" the gate is given permit to be consolidated into LTM.