The representation of spatial context

Abstract

It has been known for some time that hippocampal place cells respond not only to spatial aspects of an environment but also to non-spatial, “contextual” aspects, such as its colour. In addition, several experiments, models and theories of hippocampal function have suggested that the hippocampus has a role in processing context, be it context of a spatial nature (e.g., O'Keefe, Nadel, 1978; Nadel, Willner, 1980; Nadel et al., 1985; Redish, 2001) or context of a more general nature (e.g., Hirsh, 1974; Myers, Gluck, 1994; Rudy, O'Reilly, 1999; Rudy, O'Reilly, 2001). However, widespread usage of the term “context” in a variety of different settings has rendered the term somewhat ill-defined, and consequently of little heuristic value. We argue here in support of the view advanced by O'Keefe and Nadel (1978) and Nadel and Willner (1980) that context is a neural construct, rather than something that has a separate existence in the external world. Using data from recent recording studies of hippocampal cells in behaving rats, we propose a model of the contextual modulation of hippocampal place cells in which the contextual cues function to determine how place cells respond to their spatial inputs. We argue on the basis of these, and other, findings that the type of representation the hippocampus processes is best referred to as “spatial context” (Holland, Bouton, 1999; Good et al., 1998).