Entorrinal cortex (brain): what is it and what functions does it have?
The cerebral cortex is one of the most known structures, developed and visible in our brain, possessing a large number of functions that allow us to be who and how we are and adaptively behave in order to survive. But we are not facing a homogeneous mass that takes care of everything: different brain regions have different nerve fibers that specialize in different functions.
Although it is common to know names such as prefrontal or orbitofrontal cortex, other areas are not as popular and tend to go unnoticed despite carrying out important functions. Among the latter we can find the entorhinal cortex , which we are going to talk about in this article.
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What is the entorhinal cortex?
The entorhinal cortex is a region of the brain located in the ventromedial temporal region, specifically located in the parahippocampal gyrus caudal to the olfactory cortex of the uncus and in direct contact with the hippocampus. It includes the areas of Brodmann 28 and 34, and borders the perirrinal cortex and the lateral sulcus.
This brain region has multiple connections to different areas of the brain. Connects with the olfactory and visual pathways and with different structures of the temporal, parietal and frontal lobes (including the orbitofrontal cortex.) However, the structure with the highest level of connection is the hippocampus, serving as a relay center that distributes information that enters or leaves it and acts as a bridge between it and other areas of the brain. between hippocampus and entorhinal cortex is carried out through the so-called perforating pathway.
It is considered an area of association that ends up integrating and sending information to the hippocampus, as well as an important part of the limbic system, receiving afferences from the amygdala and contributing to the sensory information of emotional components in memory.
Principal functions
The entorhinal cortex has a very important role in our organism, allowing the realization, integration and good functioning of a large number of cognitive functions . Some of the functions in which this part of the cortex has been most involved are the following.
1. Relief center
Traditionally its best-known function, one of the multiple roles of the entorhinal cortex is that of allow information from the rest of the cortex to reach the hippocampus and in turn that which arises from the hippocampus reaches the rest of the brain.
2. Memory: formation and consolidation of memories
The entorhinal cortex is considered one of the most relevant brain nuclei in terms of memory capacity, being the bridge through which arrives and sends information to or from the hippocampus.
Is about a fundamental region in the formation and consolidation of memories In fact, lesion of the entorhinal cortex can make it difficult or even impossible to encode and record new content or information, producing anterograde amnesia.
One aspect to highlight is that this cortex is active during sleep, especially in REM, something linked to its role in the consolidation of memories in memory.
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3. Gnosias
The entorhinal cortex is not only important in the formation of memories, but also in the recognition of stimuli . And it is deeply linked to semantic memory, which dictates what are the things we see and allows us to recognize them.
4. Visual and auditory information association
This brain region also has an important role at the associative level, being an area in which auditory and visual information is integrated. In fact, through the entorhinal cortex it passes information referring to all the senses, although said information arrives directly from multimodal association areas (that is, not only the information of one direction but directly the integration of several).
5. Space navigation
Another function in which the involvement of the entorhinal cortex was observed is spatial orientation and navigation. This area is the one it lets us know in which direction we are moving , being involved in the formation of mental maps.
6. Coding of odors
The entorhinal cortex also has a relevant role in regard to the olfactory system. Specifically, has been associated with the ability to code the intensity of odor and in the association of smells with memories.
Some associated disorders
The entorhinal cortex is an important brain region whose injury can have multiple consequences and effects. Mainly memory and recognition alterations occur , but also difficulties appear at the level of orientation, visual and motor problems.
Among some of the main disorders in which we have seen the presence of lesions in the entorhinal cortex (usually together with those of the hippocampus), we can the following.
1. Amnesic syndrome
Amnestic syndrome is understood to be an alteration in memory derived from some type of brain injury (psychogenic amnesias or those produced by non-organic mental disorders are not included in the syndrome).
In the amnestic syndrome anterograde amnesia is fundamentally produced in which the subject is not able to record new information, something that may or may not be accompanied by retrograde amnesia (I do not remember previous events in the subject's life). Traditionally linked to hippocampal problems, in this type of syndromes there is usually also an important involvement of the entorhinal and perirrinal cortex.
2. Alzheimer's
Multiple authors and researchers consider that the entorhinal cortex is one of the points in which Alzheimer's originates, being one of the first areas that are affected by this disease. Specifically, neurodegeneration generated by the accumulation of tau protein is observed in the lateral part of the entorhinal cortex, as well as the formation of beta-amyloid plaques. This will later expand along the temporal cortex and finally to the rest of the brain as the disease progresses.
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3. Agnosias
Although we are not dealing with a disorder per se, but rather with a symptom, agnosia is understood as the lack of recognition of the properties of a stimulus with which we are familiar. The presence of lesions in the entorhinal cortex can hinder this process, by linking to hippocampal memory. For example, odor recognition may disappear.
Bibliographic references
- Chadwick, M.J .; Jolly, A.E .; Amos, D.P .; Hassabis, D. & Spiers, H.J. (2015). A Goal Direction Signal In the Human Entorhinal / Subicular Region. Current Biology, 25: 87-92.
- Khan, U.A .; Liu, L .; Provenzano, F.A .; Berman, D.E .; Profaci, C.P .; Sloan, R .; Mayeux, R .; Duff, K.E. & Small, S.A. (2014). Molecular drivers and cortical spread of lateral entorhinal cortex dysfunction in preclinical Alzheimer's disease. Nature Neuroscience, 17: 304-311.
- Rolls, E.T .; Kringelbach, M.L. & de-Araujo, I.E. (2003). Different representations of pleasant and unpleasant odours in the human brain. Eur J Neurosci; 18: 695-703.
- Stedman, T.L. (1990). Stedman's Medical Dictionary, 25th Edition. William & Wilkins.
