ReviewThe Human Hippocampus and Spatial and Episodic Memory

consistent with the cognitive map theory characterization Department of Anatomy and Developmental of hippocampal function (O'Keefe and Nadel, 1978, 1979). Biology The cognitive map theory proposes that the hippo-University College London campus of rats and other animals represents their envi-17 Queen Square ronments, locations within those environments, and London WC1N 3AR their contents, thus providing the basis for spatial mem-2 Wellcome Department of Imaging Neuroscience ory and flexible navigation. When it comes to humans, Institute of Neurology the theory suggests a broader function for the hippo-University College London campus, based at least in part on lateralization of func-12 Queen Square tion. The right hippocampus is still viewed as encoding London WC1N 3BG spatial relationships, but the left has the altered function United Kingdom of storing relationships between linguistic entities in the form of narratives. In addition, one or both hippocampi incorporate temporal information derived from the fron-Finding one's way around an environment and remem-tal lobes, which serves to timestamp each individual bering the events that occur within it are crucial cogni-visit to a location, thus providing the basis for a spatio-tive abilities that have been linked to the hippocampus temporal contextual or episodic memory system. and medial temporal lobes. Our review of neuropsy-The hippocampus has also been ascribed a much chological, behavioral, and neuroimaging studies of broader role in both animals and humans, encompassing human hippocampal involvement in spatial memory episodic and spatial memory along with many other concentrates on three important concepts in this field: types of memory. Primary among these broader charac-spatial frameworks, dimensionality, and orientation terizations are " declarative " memory (Squire and Zola-and self-motion. We also compare variation in hippo-Morgan, 1991), and " flexible relational " memory (Cohen campal structure and function across and within spe-and Eichenbaum, 1993). Declarative memory refers to cies. We discuss how its spatial role relates to its all forms of conscious or explicit memory, including epi-accepted role in episodic memory. Five related studies sodic, semantic, and familiarity-based recognition, with use virtual reality to examine these two types of mem-the additional suggestion that the hippocampus plays ory in ecologically valid situations. While processing a time-limited role (i.e., being needed only for recently of spatial scenes involves the parahippocampus, the acquired information). Under the flexible-relational hy-right hippocampus appears particularly involved in pothesis, hippocampal function is closely related to de-memory for locations within an environment, with the clarative memory, including all explicit memory (Eichen-left …