Entorhinal cortex (cerebrum): what is it and what are its functions?

This part of the brain is related to memory, smell and orientation.

The cerebral cortex is one of the most 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 to behave adaptively in order to survive. But we are not dealing with a homogeneous mass that takes care of everything: different brain regions have different nerve fibers that specialize in different functions.

While it is common to know names such as prefrontal or orbitofrontal cortex, other areas are not so 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.which we are going to talk about in this article.

What is the entorhinal cortex?

The entorhinal cortex is a region of the brain located in the ventromedial temporal cortex, specifically located at the the parahippocampal gyrus caudal to the olfactory cortex of the uncus and in direct contact with the hippocampus. and in direct contact with the hippocampus. It includes Brodmann's areas 28 and 34, and borders the perirhinal cortex and the 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). (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 hippocampus and entorhinal cortex is carried out through the so-called 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 afferences from the amygdala and contributing to provide sensory information with emotional components in memory.

Main functions

The entorhinal cortex plays a very important role in our organism, enabling 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. Relay center

Traditionally its best-known function, one of the multiple roles of the entorhinal cortex is that of information from the rest of the cortex to the hippocampus and, in turn, to the hippocampus. and in turn for information from the hippocampus to reach the rest of the brain.

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 information arrives and is sent to or from the hippocampus.

It is a a fundamental region in the formation and consolidation of memories.In fact, a 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 note is that this cortex is active during sleep, especially during REM sleep, something linked to its role in the consolidation of memories in memory.

3. gnosias

The entorhinal cortex is not only important in memory formation, but also in the recognition of stimuli. stimulus recognition. And it is deeply linked to semantic memory, which dictates to us what the things we see are and allows us to recognize them.

4. Association of visual and auditory information

This brain region also plays an important role at the associative level, being an area in which auditory and visual information is integrated. In fact, information from all senses passes through the entorhinal cortex, although this information comes directly from multimodal association areas. information comes directly from multimodal association areas (i.e., it does not only (i.e. not only information from one sense but directly the integration of several senses).

5. Spatial navigation

Another of the functions in which the involvement of the entorhinal cortex has been observed is in orientation and spatial navigation. This area is the one that allows us to know in which direction we move, being involved in the formation of spatial patterns.It is involved in the formation of mental maps.

6. Coding of odors

The entorhinal cortex also plays a relevant role in the olfactory system. Specifically, has been found to be associated with the ability to encode odor intensity and the and in the association of odors with memories.

Some associated disorders

The entorhinal cortex is an important brain region whose lesion can have multiple consequences and effects. Mainly memory and recognition disturbances occur, but there are also difficulties at the level of memory and recognition.but there are also difficulties in orientation, visual and motor problems.

Among some of the main disorders in which the existence of lesions in the entorhinal cortex has been observed (generally together with those of the hippocampus), we can mention the following.

1. Amnestic syndrome

Amnesic syndrome is understood as a memory alteration derived from some type of brain lesion (psychogenic amnesias or those produced by non-organic mental alterations are not included in the syndrome).

In the amnesic syndrome an anterograde amnesia occurs fundamentally, in which the subject is not in which the subject is unable to record new information, which 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 usually also 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 disease originates, being one of the first areas to be affected by this disease. Specifically, neurodegeneration generated by the accumulation of tau protein in the lateral part of the entorhinal cortex, as well as the formation of beta-amyloid plaques. in the lateral part of the entorhinal cortex, as well as the formation of beta-amyloid plaques. This will subsequently spread 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 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 may hinder this process, as it is linked to hippocampal memory. For example, odor recognition may disappear.