PROJECT SUMMARY/ABSTRACT Cigarette smoking and nicotine dependence account for more than 7 million deaths per year worldwide. A major challenge for treatments targeting smoking cessation is relapse: Most people who attempt to quit return to smoking within months. When individuals stop smoking, being in environments where they used to smoke, like bars, coffee shops, or bus stops, can trigger cravings for nicotine and lead to a return to smoking. This is known as context-induced relapse, where context refers to the physical space or social setting associated with drug use. These associative memories between contexts and nicotine are thought to be formed and retrieved by the hippocampus and dependent on nicotinic acetylcholine receptors (nAChRs), specifically β2 containing-nAChRs (β2*-nAChRs). However, the specific neuronal mechanisms underlying these nicotine-context associations in the hippocampus and their modulation by β2*-nAChRs are not yet fully understood. Studying the involvement of the hippocampus in learning these associations presents challenges, as it requires tracking the activity of the same neurons over extended periods of time (days to weeks). To address this, I propose to use large-scale imaging techniques that allow for long-term recording of neural activity in awake and behaving mice, combined with computational tools to uncover the underlying neural dynamics. My central hypotheses are 1) that the formation of nicotine-context memories in the hippocampus requires the binding of nicotine to β2*-nAChRs 2) this binding, also enables hippocampal neurons to form stable memory representations of the nicotine-context with repeated learning and 3) that stable memory traces are re-activated during context re-exposure leading to relapse. To test these hypotheses, I will combine a novel behavior paradigm to assess context-induced relapse behavior using virtual-reality in mice with two-photon imaging of large populations of hippocampal neurons. With this technique, I will track activity of the same neurons during nicotine-context learning and memory retrieval. Further, I will integrate this activity imaging with genetic techniques and pharmacological manipulations to causally examine the role of β2*-nAChRs. Through this comprehensive approach, my research aims to provide a detailed understanding of how nicotine-driven memory representations in the hippocampus contribute to context-induced relapse, at a spatial and temporal scale that has not been achieved before. This mechanistic understanding of neural computations in the hippocampus will potentially help identify novel therapeutics and relapse-prevention strategies. To achieve these goals, I will receive mentorship and support from a group of experts in various fields, including hippocampal memory processes (Dr. Mark Sheffield), nicotinic receptor function (Dr. Daniel McGehee), task design and animal behavior (Dr. Rick Bevins), genetic techniques (Dr. Xiaoxi Zhuang) and computational analys...