The MTL Memory System and Declarative Memory

While episodic memory is modulated by PFC-mediated cognitive control mechanisms, it has long been known that episodic memory (and declarative memory, more broadly) most critically depends on the operations of the MTL memory system. The MTL is composed of multiple structures, including the hippocampal formation (dentate gyrus, fields of cornu Ammonis, and subiculum) and the surrounding entorhinal (ERc), perirhinal (PRc), and parahippocampal (PHc) cortices. Though extensive research has aimed to characterize the role of MTL in declarative memory, fundamental questions remain regarding the functional contributions of specific MTL substructures. Much of the debate centers on how the MTL encodes and retrieves conjunctive representations––which constitute item-context and item-item associations that can be pattern-completed during retrieval when given partial input––and the relation between these representations and those supporting item memory––knowledge about the individual items (elements) of an event and recognition that an item is novel or familiar.