Major Dissociation Between Medial and Lateral Entorhinal Input to Dorsal Hippocampus

Abstract

Hippocampal place cells are a model system of how the brain constructs cognitive representations and of how these representations support complex behavior, learning, and memory. There is, however, a lack of detailed knowledge about the properties of hippocampal afferents. We recorded multiple single units from the hippocampus and the medial and lateral entorhinal areas of behaving rats. Although many medial entorhinal neurons had highly specific place fields, lateral entorhinal neurons displayed weak spatial specificity. This finding demonstrates a fundamental dissociation between the information conveyed to the hippocampus by its major input streams, with spatial information represented by the medial and nonspatial information represented by the lateral entorhinal cortex.

Towards a functional organization of the medial temporal lobe memory system: Role of the parahippocampal and medial entorhinal cortical areas

“…Areas that lie along the central stem constitute overlapping elements of both types of episodes. Consistent with previous reports (Fyhn et al, 2004;Hargreaves et al, 2005), MEC neuronal activity was associated with an animal's position along the maze. A strict and consistent periodic spacing in the spatial firing pattern was not observed in these cells, similar to a recent report of a breakdown in the consistent grid pattern (characterized as a ''resetting'') of MEC neuronal grid firing when animals' movements on a maze were constrained to make hairpin turns (Derdikman et al, 2006).…”

“…Studies in humans have indentified a ''parahippocampal place area'' within the parahippocampal cortex, which is activated by presentation of spatial scenes but not single or multiple objects (Epstein and Kanwisher, 1998;Epstein, 2005). In rats, while perirhinal and LEC neurons have poor spatial coding properties, MEC neurons show strong spatial coding (Quirk et al, 1992;Fyhn et al, 2004;Hargreaves et al, 2005), and there is some evidence of weak spatial firing in the postrhinal cortex Burwell and Hafeman, 2003). In particular, the MEC is the location of the grid cells, boundary cells, and head direction cells that reflect different aspects of spatial processing (Sargolini et al, 2006;Moser and Moser, 2008;Solstad et al, unpublished).…”

A metric for space

“…The function of the lateral entorhinal cortex is currently unsettled. Grid cells have not been observed in this region (Hargreaves et al, 2005). The apparently nonspatial firing properties of lateral entorhinal neurons is consistent with the absence of input to this region from head direction cells in the presubiculum , although position may still be represented in ways not detectable in time-averaged rate maps.…”

Comparative Cognition, Hippocampal Function, and Recollection

“…Whereas perirhinal and lateral entorhinal neurons have poor spatial coding properties, parahippocampal and medial entorhinal neurons show strong spatial coding (Burwell & Hafeman, 2003;Hargreaves, Rao, Lee, & Knierim, 2005). Furthermore, the immediate early gene fos is activated in the perirhinal cortex by novel visual cues, but fos is activated in the postrhinal cortex by a spatial re-arrangement of the cues (Wan, Aggleton, & Brown, 1999).…”