The primary goal of the proposed research is to explore the functional roles in memory retrieval of structures within the medial temporal lobe, including the hippocampus and adjacent structures. The proposal builds on recent work by the investigators positing a new view of medial temporal lobe involvement in memory consolidation, storage, and retrieval, referred to as Multiple Trace Theory (MTT). Tradition holds that the role of medial temporal lobe structures in memory is time-limited, lasting only until consolidation of the memory trace in neocortex is complete, after which memories can be retained and retrieved without hippocampal involvement. MTT, in contrast, argues that the hippocampus plays a lasting role in the storage and retrieval of memory, and that the central role of the hippocampus reflects its essential role in the processing of various types of spatial information. The proposed studies will ask whether the hippocampus plays a special role in the retrieval of three kinds of spatial information important to personal memories: spatial context, spatial location, and spatial relations. The studies will also explore the various forms of personal or episodic memory, comparing personal memory to world knowledge or semantic memory. Healthy adults will participate in a series of experiments, using functional magnetic resonance imaging fMRI). While in the scanner, they will be asked to recollect personal experiences, recently learned information, and well-established world knowledge, in order to compare activation within medial temporal and neocortical brain structures during retrieval of these varied types of memories. Some memories will include spatial information or spatial relations, while others will not. The study will not only directly test some of the assertions from MTT, but it will also provide important information regarding the neural mechanisms underlying long-term storage and retrieval in humans. ? ?
