Considerable recent progress in anatomical, neuropsychological, and neurophysiological studies on humans and animals have confirmed the importance of the hippocampal system in memory, and many of these studies have suggested that distinct components of this system may make different contributions. However, this view is controversial and the precise nature of the contributions of cortical areas surrounding the hippocampus (the parahippocampal region) and the hippocampus itself are not well understood. In the proposed work, we will take advantage of recently developed animal models of hippocampal memory function and employ state-of-the-art multi-channel recording and population analysis methods. Using these methods we will characterize neural representations in subregions of the hippocampus and surrounding cortical areas of animals performing episodic recognition, pattern separation, and pattern completion operations for which performance depends on hippocampal function. We will investigate the hypothesis that the hippocampus rapidly encodes stimuli in the context in which they are experienced whereas separate areas within the surrounding parahippocampal region encode individual stimuli and contextual cues. Furthermore, we will explore the nature of interactions between the hippocampus and cortex, testing the hypothesis that the hippocampus supports the cued recovery of contextual representations within the cortex. These characterizations of individual and combined network processing in the hippocampus and surrounding cortex will improve our understanding of the normal functions of this system as well as its breakdown in memory disorders.
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