The hippocampus and mechanisms of declarative memory

The hippocampus is critical to declarative memory in humans and spatial mem ory in rodents. This review attempts to bridge between these two characteri zations of hippocampal dependent memory, and in doing so reveal fundamental cognitive and neural coding mechanisms that are common to both. Evidence i s presented that the hippocampus and its connections are critical to the es tablishment of a systematic organization of memories and to flexible expres sion of memory outside repetition of the training experience. In addition, evidence is presented that hippocampal neurons encode a broad range of expe rience and that these codings may be organized as representations of episod es in memory. It is suggested that these episodic codings are linked by com mon elements to construct an organized representation of acquired knowledge . (C) 1999 Elsevier Science B.V. All rights reserved.