entorhinal cortex

The entorhinal cortex is a portion of the rostral parahippocampal gyrus.{{Cite book |last=Martin |first=John D. |title=Neuroanatomy: Text and Atlas |publisher=McGraw Hill |year=2020 |isbn=978-1-259-64248-7 |edition=5th |location=New York |page=381}}

It is usually divided into medial and lateral regions with three bands with distinct properties and connectivity running perpendicular across the whole area. A distinguishing characteristic of the EC is the lack of cell bodies where layer IV should be; this layer is called the Lamina dissecans.

File:Apoe-cortical-thickness-entorhinal.jpg

The superficial layers – layers II and III – of EC project to the dentate gyrus and hippocampus: Layer II projects primarily to dentate gyrus and hippocampal region CA3; layer III projects primarily to hippocampal region CA1 and the subiculum. These layers receive input from other cortical areas, especially associational, perirhinal, and parahippocampal cortices, as well as prefrontal cortex. EC as a whole, therefore, receives highly processed input from every sensory modality, as well as input relating to ongoing cognitive processes, though it should be stressed that, within EC, this information remains at least partially segregated.

The deep layers, especially layer V, receive one of the three main outputs of the hippocampus and, in turn, reciprocate connections from other cortical areas that project to superficial EC.

• Brodmann area 28 is known as the "area entorhinalis"
• Brodmann area 34 is known as the "area entorhinalis dorsalis"

In 2005, it was discovered that entorhinal cortex contains a neural map of the spatial environment in rats.{{cite journal |vauthors=Hafting T, Fyhn M, Molden S, Moser M, Moser E |s2cid=4405184 |title=Microstructure of a spatial map in the entorhinal cortex |journal=Nature |volume=436 |issue=7052 |pages=801–6 |year=2005 |pmid=15965463 | doi = 10.1038/nature03721 |bibcode=2005Natur.436..801H}} In 2014, John O'Keefe, May-Britt Moser and Edvard Moser received the Nobel Prize in Physiology or Medicine, partly because of this discovery.{{cite web|title=Overview of Nobel Prize laureates in Physiology or Medicine|url=https://www.nobelprize.org/nobel_prizes/medicine/laureates/}}

In rodents, neurons in the lateral entorhinal cortex exhibit little spatial selectivity,{{cite journal |vauthors=Hargreaves E, Rao G, Lee I, Knierim J |s2cid=24399770 |title=Major dissociation between medial and lateral entorhinal input to dorsal hippocampus |journal=Science |volume=308 |issue=5729 |pages=1792–4 |year=2005 |pmid=15961670 |doi=10.1126/science.1110449|bibcode = 2005Sci...308.1792H }} whereas neurons of the medial entorhinal cortex (MEC), exhibit multiple "place fields" that are arranged in a hexagonal pattern, and are, therefore, called "grid cells". These fields and spacing between fields increase from the dorso-lateral MEA to the ventro-medial MEA.{{cite journal |vauthors=Fyhn M, Molden S, Witter M, Moser E, Moser M |title=Spatial representation in the entorhinal cortex |journal=Science |volume=305 |issue=5688 |pages=1258–64 |year=2004 |pmid=15333832 |doi=10.1126/science.1099901 |bibcode=2004Sci...305.1258F|doi-access= }}

The same group of researchers has found speed cells in the medial entorhinal cortex of rats. The speed of movement is translated from proprioceptive information and is represented as firing rates in these cells. The cells are known to fire in correlation to future speed of the rodent.{{cite journal |author1=Kropff Em |author2=Carmichael J E |author3=Moser M-B |author4=Moser E-I |s2cid=4404374 | year = 2015 | title = Speed cells in the medial entorhinal cortex | journal = Nature | volume = 523 |issue=7561 | pages = 419–424 | doi = 10.1038/nature14622 |pmid=26176924 |bibcode = 2015Natur.523..419K |hdl=11336/10493 |hdl-access=free }}

Recently, a general theory has been proposed to elucidate the function of the reelin positive cells in the layer II of the entorhinal cortex. According to this concept, these cells would be generally organized into 1-dimensional ring attractors, and in the medial (in humans: posteromedial) portion, would function as grid cells (anatomically: stellate cells) while in lateral (in humans: anterolateral) portion, where they appear as fan cells, would enable the encoding of new episodic memories.{{cite journal | vauthors = Kovács KA | title = Episodic Memories: How do the Hippocampus and the Entorhinal Ring Attractors Cooperate to Create Them? | journal = Frontiers in Systems Neuroscience | volume = 14 | page = 68 | date = September 2020 | doi = 10.3389/fnsys.2020.559186 | pmid = 33013334 | pmc = 7511719 | doi-access = free }} This concept is underscored by the fact that fan cells of the entorhinal cortex are indispensable for the formation of episodic-like memories in rodents.{{cite journal |vauthors=Vandrey B, Garden DL, Ambrozova V, McClure C, Nolan MF, Ainge JA | title = Fan cells in layer 2 of the lateral entorhinal cortex are critical for episodic-like memory. | journal = Current Biology | volume = 30 | pages = 169–175.e5 | date = January 2020 | issue = 1 | doi = 10.1016/j.cub.2019.11.027 | pmid = 31839450 | pmc = 6947484 | doi-access = free }}

Single-unit recording of neurons in humans playing video games find path cells in the EC, the activity of which indicates whether a person is taking a clockwise or counterclockwise path. Such EC "direction" path cells show this directional activity irrespective of the location of where a person experiences themselves, which contrasts them to place cells in the hippocampus, which are activated by specific locations.{{cite journal |vauthors=Jacobs J, Kahana MJ, Ekstrom AD, Mollison MV, Fried I | year = 2010 | title = A sense of direction in human entorhinal cortex | journal = Proc Natl Acad Sci U S A | volume = 107 | issue = 14| pages = 6487–6492 | doi = 10.1073/pnas.0911213107 | pmid = 20308554 | pmc=2851993|bibcode = 2010PNAS..107.6487J | doi-access = free }}

EC neurons process general information such as directional activity in the environment, which contrasts to that of the hippocampal neurons, which usually encode information about specific places. This suggests that EC encodes general properties about current contexts that are then used by hippocampus to create unique representations from combinations of these properties.

Research generally highlights a useful distinction in which the medial entorhinal cortex (MEC) mainly supports processing of space,{{Cite journal|title=Cellular mechanisms of spatial navigation in the medial entorhinal cortex|journal=Nature|volume=16|issue=3|pages=325–331|doi=10.1038/nn.3340|pmid=23396102|year=2013|last1=Schmidt-Hieber|first1=Christoph|last2=Häusser|first2=Michael|s2cid=13774938}} whereas the lateral entorhinal cortex (LEC) mainly supports the processing of time.

The MEC exhibits a strong ~8 Hz rhythmic neural activity known as theta. Alterations in the neural activity across the brain region results in an observed "traveling wave" phenomena across the MEC long-axis, similar to that of the hippocampus,{{cite journal |last1=Lubenov |first1=Evgueniy V. |last2=Siapas |first2=Athanassios G. |s2cid=4429491 |title=Hippocampal theta oscillations are travelling waves |journal=Nature |date=17 May 2009 |volume=459 |issue=7246 |pages=534–539 |doi=10.1038/nature08010|pmid=19489117 |bibcode=2009Natur.459..534L |url=https://authors.library.caltech.edu/14755/1/Lubenov2009p4508Nature.pdf }} due to asymmetric theta oscillations.{{cite journal |vauthors=Hernández-Pérez JJ, Cooper KW, Newman EL| title=Medial entorhinal cortex activates in a traveling wave in the rat. | journal=eLife | year= 2020 | volume= 9 | pmid=32057292 | doi=10.7554/eLife.52289 | pmc=7046467 | doi-access=free }} The underlying cause of these phase shifts and their waveform changes is unknown.

Individual variation in the volume of EC is linked to taste perception. People with a larger EC in the left hemisphere found quinine, the source of bitterness in tonic water, less bitter.{{cite journal |vauthors=Hwang LD, Strike LT, Couvy-Duchesne B, de Zubicaray GI, McMahon K, Bresline PA, Reed DR, Martin NG, Wright MJ | year = 2019 | title = Associations between brain structure and perceived intensity of sweet and bitter tastes | journal = Behav. Brain Res. | volume = 2 |issue=363 | pages = 103–108 | doi = 10.1016/j.bbr.2019.01.046 |pmid= 30703394 | pmc = 6470356 }}

The entorhinal cortex is the first area of the brain to be affected in Alzheimer's disease; in year 2013, a functional magnetic resonance imaging study has localised the area to the lateral entorhinal cortex.{{cite journal|vauthors=Khan UA, Liu L, Provenzano FA, Berman DE, Profaci CP, Sloan R, Mayeux R, Duff KE, Small SA |year=2013|title=Molecular drivers and cortical spread of lateral entorhinal cortex dysfunction in preclinical Alzheimer's disease|journal=Nature Neuroscience|doi=10.1038/nn.3606|volume=17|issue=2|pages=304–311|pmc=4044925|pmid=24362760}} Lopez et al.{{cite journal|last1=Lopez|first1=M. E.|last2=Bruna|first2=R.|last3=Aurtenetxe|first3=S.|last4=Pineda-Pardo|first4=J. A.|last5=Marcos|first5=A.|last6=Arrazola|first6=J.|last7=Reinoso|first7=A. I.|last8=Montejo|first8=P.|last9=Bajo|first9=R.|last10=Maestu|first10=F.|title=Alpha-Band Hypersynchronization in Progressive Mild Cognitive Impairment: A Magnetoencephalography Study|journal=Journal of Neuroscience|date=2014|volume=34|issue=44|pages=14551–14559|doi=10.1523/JNEUROSCI.0964-14.2014|pmid=25355209|pmc=6608420}} have shown, in a multimodal study, that there are differences in the volume of the left entorhinal cortex between progressing (to Alzheimer's disease) and stable mild cognitive impairment patients. These authors also found that the volume of the left entorhinal cortex inversely correlates with the level of alpha band phase synchronization between the right anterior cingulate and temporo-occipital regions.

In 2012, neuroscientists at UCLA conducted an experiment using a virtual taxi video game connected to seven epilepsy patients with electrodes already implanted in their brains, allowing the researchers to monitor neuronal activity whenever memories were being formed. As the researchers stimulated the nerve fibers of each of the patients' entorhinal cortex as they were learning, they were then able to better navigate themselves through various routes and recognize landmarks more quickly. This signified an improvement in the patients' spatial memory.{{cite journal|last1=Suthana|first1=N.|last2=Haneef|first2=Z.|last3=Stern|first3=J.|last4=Mukamel|first4=R.|last5=Behnke|first5=E.|last6=Knowlton|first6=B.|last7=Fried|first7=I.|year=2012|title=Memory Enhancement and Deep-Brain Stimulation of the Entorhinal Area|journal=New England Journal of Medicine|doi=10.1056/NEJMoa1107212|volume=366|issue=6|pages=502–510|pmc=3447081|pmid=22316444}}

Effect of aerobic exercise

A study on young subjects found aerobic fitness to be positively correlated with entorhinal cortex volume, indicating that aerobic exercise may have a positive effect on the medial temporal lobe memory system (which includes the entorhinal cortex).{{Cite news|url=https://m.medicalxpress.com/news/2015-12-highlights-importance-physical-aerobic-healthy.html|title=Study highlights the importance of physical activity and aerobic exercise for healthy brain function|access-date=2017-12-04}}

In rodents, the EC is located at the caudal end of the temporal lobe. The rodent entorhinal cortex shows a modular organization, with different properties and connections in different areas.

In primates it is located at the rostral{{Broken anchor|date=2025-03-24|bot=User:Cewbot/log/20201008/configuration|target_link=Anatomical terms of location#Cranial and caudal|reason= The anchor (Cranial and caudal) has been deleted.|diff_id=1175671216}} end of the temporal lobe and stretches dorsolaterally.

File:Entorhinal - DK ATLAS.png|Entorhinal cortex, shown in the right cerebral hemisphere.

{{Reflist}}

{{Commons category|Entorhinal cortex}}

• {{BrainMaps|Entorhinal%20cortex|Entorhinal cortex}}
• [https://www.neuinfo.org/mynif/search.php?q=Entorhinal%20Cortex&t=data&s=cover&b=0&r=20 NIF Search - Entorhinal Cortex] via the Neuroscience Information Framework
• For delineating the Entorhinal cortex, see Desikan RS, Ségonne F, Fischl B, Quinn BT, Dickerson BC, Blacker D, Buckner RL, Dale AM, Maguire RP, Hyman BT, Albert MS, Killiany RJ. An automated labeling system for subdividing the human cerebral cortex on MRI scans into gyral based regions of interest. Neuroimage. 2006 Jul 1;31(3):968-80.

{{Cerebral cortex}}

{{Papez circuit}}

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Category:Limbic system

Category:Cerebral cortex

Category:Temporal lobe