3-B-P-031 〇浅岡 希美、林 康紀 Nozomi Asaoka, Yasunori Hayashi 京都大・院医・システム神経薬理 Dept. Pharmacol., Grad. Sch. Med., Kyoto Univ. Much of our decision-making relies on habit, which is formed by repetition of motivational goal-directed action. Because of stability and low cognitive demands, most habits are beneficial, while maladaptive habits performed excessively are known to be a cause of psychiatric symptoms, such as compulsivity. Generally, the execution of the action often declines as it becomes habitual, while a subset of individuals maintains a high rate of execution. The neural mechanisms underlying such individuality remain unclear. Here, we developed a 2-step task where mice initially learn goal-directed lever press and then seamlessly moved to a task with an unpredictable rule between lever-press and reward delivery which facilitates habit formation. Whereas a half of the mice reduced the frequency in the 2nd step, the rest maintained a frequency comparable to the 1st step. We then assessed task-induced synaptic plasticity and found habit formation-related significant changes in the AMPA/NMDA ratio in the lateral orbitofrontal cortex (lOFC) and anterior cingulate cortex (ACC). Chemogenetic manipulation revealed the lOFC maintains the frequency of habitual lever-press, whereas whether the lever-press becomes habit depends on the ACC. Optogenetic erasure of the synaptic potentiation in striatum-projecting lOFC neurons disrupted the maintenance of lever-press frequency. Collectively, the formation of habit and its frequency are controlled by distinct cortical regions and synaptic potentiation in the lOFC during habit formation determines habit individuality.