Hippocampal and neocortical interactions during context discrimination: Electrophysiological evidence from the rat

There is substantial evidence that hippocampus plays an important role in the processing of contextual information. its specific role, however, remains unclear. One possibility is that single hippocampal neurons represent context information so that local circuits can construct representations of the current context, and the context that is expected based on past experience. Population codes derived from input by multiple local circuits may then engage match-mismatch algorithms that compare current and expected context information to determine the extent to which an expected context has changed. The results of such match-mismatch comparisons can be used to discriminate contexts. When context changes are detected, efferent messages may be passed on to connected neocortical areas so that informed "decisions" regarding future behavioral and cognitive strategies can be made. Here, a brief review describes evidence that a primary consequence of hippocampal processing is the discrimination of meaningful contexts. Then, the functional significance of neocortical circuits that likely receive hippocampal output messages are described in terms of their contribution to the control of ongoing behavioral and cognitive strategy, especially during active navigation. it is clear from this systems view that studies of spatial navigation continue to provide researchers with an excellent model of hippocampal-neocortical interactions during learning. (C) 2007 Wiley-Liss, Inc.