Complementary Functional Organization of Neuronal Activity Patterns in the Perirhinal, Lateral Entorhinal, and Medial Entorhinal Cortices

Abstract

It is commonly conceived that the cortical areas of the hippocampal region are functionally divided into the perirhinal cortex (PRC) and the lateral entorhinal cortex (LEC), which selectively process object information; and the medial entorhinal cortex (MEC), which selectively processes spatial information. Contrary to this notion, in rats performing a task that demands both object and spatial information processing, single neurons in PRC, LEC, and MEC, including those in both superficial and deep cortical areas and in grid, border, and head direction cells of MEC, have a highly similar range of selectivity to object and spatial dimensions of the task. By contrast, representational similarity analysis of population activity reveals a key distinction in the organization of information in these areas, such that PRC and LEC populations prioritize object over location information, whereas MEC populations prioritize location over object information. These findings bring to the hippocampal system a growing emphasis on population analyses as a powerful tool for characterizing neural representations supporting cognition and memory.

Viewpoints: how the hippocampus contributes to memory, navigation and cognition

“…This work nicely complements findings from Keene et al . 110 showing that MEC neurons carry considerable information about time, spatial context, spatial location, and the locations of objects in an environment.…”

Anterolateral Entorhinal Cortex Volume Predicted by Altered Intra-Item Configural Processing

“…specific, and cells responsive to combinations of spatial and object-specific dimensions are not strictly separated in the two halves of the ERC; rather, they are widely distributed over both regions (Keene et al, 2016). Further work is necessary to pinpoint definitively the functional heterogeneity of the ERC and the corresponding spatial distribution of these functional subregions.…”

“…Both postmortem histology (Braak and Braak, 1991) and in vivo cerebral blood flow imaging (Khan et al, 2014) show that Alzheimer's disease pathology appears earliest in the alERC. Similarly, morphometric analysis shows that the earliest preclinical Alzheimer's disease atrophy can also be found in the alERC (Miller et al, 2015), suggesting that alERC volume may be a sensitive biomarker for preclinical Alzheimer's disease.…”

“…Critically, the alERC overlaps significantly with the regions described as transentorhinal cortex (Braak and Braak, 1991) or lateral entorhinal cortex (Khan et al, 2014), which exhibit Alzheimer's disease pathology earlier than any other brain region. Despite the clinical importance of alERC decline, no human studies to date have attempted to link alERC volume to particular cognitive functions.…”

Time (and space) in the hippocampus

“…These discoveries have led to a widely held view that the hippocampus and neighboring areas compose a brain system that maps space and guides spatial navigation[1,2], heralded as “the brain’s GPS” in the announcement of the Nobel Prize for Physiology or Medicine for 2014. While new discoveries have confirmed that the hippocampus does indeed create maps of space and where events important events occur[3, 4] and these maps surely serve navigation to desired goals, the scope of hippocampal function in memory goes well beyond organizing memories in space[5,6]. …”