The CA3 subregion of the hippocampus is critical for episodic memory processing by means of relational encoding in rats.

This experiment tested the theory that the CA3 subregion of the hippocampus mediates episodic learning of arbitrary associations. The authors developed 2 tasks based on the episodic flavor-place paired-associate task described by M. Day, R. Langston, and R. G. Morris (2003): an object-cued spatial location recall task and a spatial location-cued object recall task. After rats were trained to a criterion of 80% correct on 1 of the 2 tasks, they received either a dorsal CA3 lesion or a vehicle control lesion. Control animals continued performing well on both tasks. Rats with lesions to dorsal CA3 were impaired on both tasks and performed at chance but were able to perform a nonepisodic version of the task as a control. These data suggest that CA3 mediates episodic learning of arbitrary associations as tested in the 1-trial object-cued spatial location recall and spatial location-cued object recall tasks.

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