Distinct Roles of Medial and Lateral Entorhinal Cortex in Spatial Cognition

Abstract

It is known that the entorhinal cortex plays a crucial role in spatial cognition in rodents. Neuroanatomical and electrophysiological data suggest that there is a functional distinction between 2 subregions within the entorhinal cortex, the medial entorhinal cortex (MEC), and the lateral entorhinal cortex (LEC). Rats with MEC or LEC lesions were trained in 2 navigation tasks requiring allothetic (water maze task) or idiothetic (path integration) information processing and 2-object exploration tasks allowing testing of spatial and nonspatial processing of intramaze objects. MEC lesions mildly affected place navigation in the water maze and produced a path integration deficit. They also altered the processing of spatial information in both exploration tasks while sparing the processing of nonspatial information. LEC lesions did not affect navigation abilities in both the water maze and the path integration tasks. They altered spatial and nonspatial processing in the object exploration task but not in the one-trial recognition task. Overall, these results indicate that the MEC is important for spatial processing and path integration. The LEC has some influence on both spatial and nonspatial processes, suggesting that the 2 kinds of information interact at the level of the EC.

Impaired Path Integration and Grid Cell Spatial Periodicity in Mice Lacking GluA1-Containing AMPA Receptors

“…Orientation based on idiothetic cues, also termed path integration, requires the animal to integrate its rotational and translational movements during an excursion to estimate its current position relative to a starting point. Ablation studies suggest that the hippocampus and the parahippocampal region are involved in path integration (Whishaw and Maaswinkel, 1998;Maaswinkel et al, 1999;Parron and Save, 2004;Van Cauter et al, 2013).…”

“…Only clusters with stable features and a clear refractory period in their spike-time autocorrelation were analyzed. Separation between clusters was estimated by the isolation distance (Schmitzer-Torbert et al, 2005). Putative excitatory cells were distinguished from putative interneurons based on their mean firing rate.…”

“…A peak in the autocorrelation matrix was defined as Ͼ10 adjacent bins with a correlation coefficient higher than a peak detection threshold that was set to 0.1. The periodicity in the spatial autocorrelation matrix was estimated by the grid score (Sargolini et al, 2006). A circular region of the spatial autocorrelation matrix containing up to six peaks, but excluding the central peak, was defined.…”

How Does the Brain Solve the Computational Problems of Spatial Navigation?

“…(f) Place fields formed by summation of multiple grid cells (black sheets in the MEC indicate different grid cell modules; yellow blobs indicate active neurons in each module). (g) Place fields formed by summation of BVC inputs, which convey information about distance and direction to geometric boundaries Parron and Save 2004a, b;Steffenach et al 2005;Van Cauter et al 2012). The EC is the cortical gateway of inputs to the hippocampus: the medial and lateral portions of EC (MEC and LEC, respectively) project to the proximal and distal portions of CA1, respectively, but have overlapping projections at the dentate gyrus (DG) and CA3 (Witter and Amaral 2004;Witter et al 2006;McNaughton and Barnes 1977).…”

“…Several models placed the locus of path integration within the CA1/CA3 network itself, suggesting how the hippocampus might integrate velocity inputs, for example, through the use of sinusoidal arrays or continuous attractor networks (Tsodyks and Sejnowski 1995;Samsonovich and McNaughton 1997). However, lesion studies Van Cauter et al 2012), the discovery of grid cells (Hafting et al 2005), theoretical considerations about the limited spatial range and resolution of the hippocampal code , and models of path integration by grid cells (Fuhs and Touretzky 2006;Guanella et al 2007;Burak and Fiete 2009;Burgess et al 2007;Hasselmo 2008), point instead to the MEC as the locus of path integration, leaving to the hippocampus the still-formidable function of synthesizing information from multiple sensory streams and constructing associations between them.…”