A theory about one part of this structure posits that, like the cerebellum, it engages in pattern separation by expansion recoding. The perforant path provides input to this structure from the entorhinal cortex. This structure receives signals from the medial septum via the fornix that help regulate theta wave generation. Molecular, granule cell, and polymorphic layers make up part of a formation named for this structure. Synapses between this structure’s CA1 and CA3 regions are often used to study long-term potentiation. This structure’s dentate gyrus is a commonly studied site of adult neurogenesis. Lesions in the uncus, amygdala, and this structure in patient H. M. caused severe anterograde amnesia. (10[1])For 10 points, name this seahorse-shaped (10[1])brain (10[1])structure (10[1])important in forming memories. ■END■ (10[1])