Distinctive neuromodulator mechanisms to explore a new environment and recognize it a few minutes later.

Neuromodulators play important roles in complex behaviors, including the balance between exploration and exploitation and the regulation of learning and memory. Although learning generalization is a critical process, its mechanisms remain poorly understood. We established a paradigm to investigate three distinct processes: exploration of a novel context, habituation memory, and recognition memory. Here, we used optogenetic tools to activate (ReaChR) or inhibit (GtACR2) neurons in freely behaving flies. We evaluated dopaminergic, serotonergic, and octopaminergic signaling, as well as brain structures, including the mushroom bodies (MBs) our results show that dopamine bidirectionally modulates habituation: activation reduces habituation, whereas inhibition facilitates it.These effects were not associated with motoneuron neuromodulation. In contrast, inhibition of serotonergic neurons impaired habituation and recognition memory, with reduced and highly variable responses. Manipulation of octopaminergic neurons did not significantly affect these processes. Silencing MBs produced similar variability and memory impairment, suggesting distinct roles for dopamine, serotonin, and MBs in this learning scenario. Finally, optogenetic activation of adenylate cyclase in MBs reduced recognition memory, supporting a role for cAMP signaling in recognition memory, while habituation may involve additional mechanisms. Further experiments are needed to clarify these mechanisms.