PROJECT SUMMARY Observational learning is a type of social learning and a fundamental cognitive behavior in humans and social animals. How neural circuits in the brain enable this type of learning is not understood. Utilizing an observational spatial working memory task, where an observer rat learns to first observe the spatial trajectory of a demonstrator rat and then run the trajectory itself for rewards, this project studies the behavioral and neural circuit processes underlying reward-directed observational learning. We will focus on a neural circuit hypothesis that interactions between the hippocampus (HP) and the anterior cingulate cortex (ACC) acquire a vicarious reward signal during observation and maintain a plan afterward for future spatial trajectories. By conducting behavioral testing, simultaneous high-density tetrode recording, and closed-loop electrical and optogenetic manipulations in animals performing the observational spatial working memory task, we will determine key behavioral factors involved, underlying neural activity patterns and their interactions in HP and ACC, and how behavioral performances are altered by time- and activity-specific disruptions of HP or ACC neurons. The outcomes of this study will significantly advance our understanding of behavioral and neural mechanisms in observational learning. The neural circuit knowledge produced and the manipulations tested in this project may generate novel insights into how observational leaning is impaired in psychiatric disorders.