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

Abstract

ABSTRACT: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. V V C 2007 Wiley-Liss, Inc.

A behavioral analysis of the impact of voluntary physical activity on hippocampus‐dependent contextual conditioning

“…Generalization occurs when an animal responds to a new stimulus with the conditioned response (such as freezing) following conditioning to a different stimulus (Domjan, 1993). The hippocampus supports the ability to distinguish between contexts (Desmedt et al, 2003; Frankland et al, 1998; Mizumori et al, 2007), thus reduced generalization in physically active animals would be consistent with improved hippocampal function. Finally, prior studies investigating the effects of voluntary physical activity on contextual conditioning used parameters that optimized conditioning, such as long context pre-exposure times (at least 3 minutes) and multiple shock presentations.…”

Integrative hippocampal and decision-making neurocircuitry during goal-relevant predictions and encoding

“…A context discrimination hypothesis (CDH) postulates that single hippocampal neurons provide multidimensional (context-defining) data for population-based network computations that ultimately determine whether expected contextual features of a situation have changed (e.g., Mizumori, 2008a,b;Mizumori et al, 1999Mizumori et al, , 2000Mizumori et al, , 2007Smith and Mizumori, 2006a,b). Specifically, hippocampal representations of spatial context information (Nadel and Payne, 2002;Nadel and Wilner, 1980;O'Keefe and Nadel, 1978) may contribute to a match-mismatch type of analysis that results in a context-prediction error signal if the context that an animal encounters is different from that expected based on past experiences (e.g., Anderson and Jeffery, 2003;Gray, 1982Gray, , 2000Hasselmo, 2005b;Hasselmo et al, 2002;Jeffery et al, 2004;Lisman and Otmakhova, 2001;Manns et al, 2007a;Mizumori et al, 1999Mizumori et al, , 2000Smith and Mizumori, 2006a,b;Nadel, 2008;Vinogradova, 1995).…”

Cues, context, and long-term memory: the role of the retrosplenial cortex in spatial cognition

“…The context is traditionally defined as the set of continuously present background cues and is closely related to the idea of spatial representations (Nadel et al, 1985; Mizumori et al, 2007). Many of the brain regions known to be involved in spatial navigation also play a prominent role in processing contextual information.…”