Entorhinal Cortex (brain): What Is It And What Functions Does It Have?
The cerebral cortex is one of the most well-known, developed and visible structures of our brain, possessing a large number of functions that allow us to be who and how we are and behave adaptively in order to survive. But we are not facing a homogeneous mass that is in charge 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.
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 Brodmann’s areas 28 and 34, and borders the perirhinal cortex and lateral sulcus.
This brain region has multiple connections with different areas of the brain. It 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 which it has the highest level of connection is the hippocampus, serving as a relay center that distributes the information that enters or leaves it and acting as a bridge between it and other areas of the brain. The link between the hippocampus and the entorhinal cortex is carried out through what is known as the perforant pathway.
It is considered an association area that finishes integrating and sending information to the hippocampus, as well as a relevant part of the limbic system, receiving input from the amygdala and contributing to providing sensory information with emotional components in memory.
Principal functions
The entorhinal cortex has a very important role in our body, allowing the realization, integration and proper 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. Respite center
Traditionally its best known function, one of the multiple roles of the entorhinal cortex is to 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 when it comes to memory capacity, being the bridge through which information arrives and is sent to or from the hippocampus.
Is about a fundamental region in the formation and consolidation of memories In fact, damage to 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.
3. Gnosias
The entorhinal cortex is not only important in the formation of memories, but also in stimulus recognition And it is deeply linked to semantic memory, which tells us what the things we see are and allows us to recognize them.
This brain region also has an important role at the associative level, being an area in which auditory and visual information is integrated. In reality, information relating to all the senses passes through the entorhinal cortex, although this information arrives directly from multimodal association areas (that is, information from one sense does not arrive only, but directly the integration of several).
5. Space navigation
Another function in which the involvement of the entorhinal cortex was observed is in spatial orientation and navigation. This area is the one that It allows us to know in which direction we are moving being involved in the formation of mental maps.
6. Smell coding
The entorhinal cortex also has a relevant role when it comes to the olfactory system. Specifically, has been associated with the ability to encode the intensity of the 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 difficulties also appear at the level of orientation, visual and motor problems.
Among some of the main disorders in which the existence of lesions in the entorhinal cortex (generally together with those of the hippocampus) has been seen, we can find the following.
1. Amnestic syndrome
Amnestic syndrome is understood as a memory alteration derived from some type of brain injury (psychogenic amnesia or amnesia produced by non-organic mental alterations are not included in the syndrome).
In amnestic syndrome basically anterograde amnesia occurs in which the subject is not able to record new information, something that may or may not be accompanied by retrograde amnesia (no memory of previous events in the subject’s life). Traditionally linked to hippocampal problems, in this type of syndromes there is also usually significant involvement of the entorhinal and perirhinal cortex.
2. Alzheimer’s
Multiple authors and researchers consider that the entorhinal cortex is one of the points where Alzheimer’s originates, being one of the first areas to be 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 subsequently expand throughout the temporal cortex and finally to the rest of the brain as the disease progresses.
3. Agnosias
Although we are not dealing with a disorder in itself but rather 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, as it is linked to hippocampal memory. For example, recognition of smells may disappear.
