Chapter 1.1 Perspectives on episodic and semantic memory retrieval

Episodic or autobiographical recollection involves re-experiencing a past event that is specific in time and place, while semantic recollection is concerned with facts and general knowledge about the world. Several prominent memory theories posit that the hippocampus differentiates between these two types of memories, mediating episodic, but not semantic, retrieval. In this chapter we explore a different view of hippocampus, one that emphasizes a singular response of the hippocampus during memory encoding and retrieval of both episodic and semantic memories, based on an amalgam of two existing theories of hippocampal function, multiple trace theory (MTT; Nadel & Moscovitch, 1997), and cognitive map theory (O'Keefe & Nadel, 1978). We review neuropsychological and neuroimaging literature suggesting that both semantic and episodic memory retrieval engages the hippocampus, at least within the normally functioning brain. We then describe an updated version of MTT that incorporates these new findings. Finally, we explore the notion that differences in the role the hippocampus plays in these forms of memory reflect two critical factors - the nature of the information being retrieved, and the requirements of the retrieval task.