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Mamillary bodies (brain region): definition, location and functions

Mamillary bodies (brain region): definition, location and functions

November 11, 2022

The human brain is made up of a set of organs, some of which are so small that it is not easy to recognize them at first sight. Mamillary bodies are one of these.

In this article we will see what are the mammillary bodies, what is their function in the encephalon and how it relates to various parts of the brain.

  • Related article: "Parts of the human brain (and functions)"

What are mamillary bodies?

The mammillary bodies are a pair of small spherical brain structures that they are located in the limbic system , the part of the brain that is responsible for generating and regulating emotions.

Specifically, they are located in the fornix, also called trine, an area that connects the hippocampus (responsible for managing the storage and recovery of memories) with the diencephalon, the latter being a structure located right in the middle of the brain and responsible for many vital tasks.

As for the composition of the mammillary bodies themselves, consists of a group of neuronal nuclei , that is, units in which different neurons are grouped together according to the tasks in which they participate (which, although they may be very similar, differ in different aspects).

  • Maybe you're interested: "Limbic system: the emotional part of the brain"

The connections of these areas of the brain

The mamillary bodies, being located in the cerebral trine, intervene in mental processes associated with emotions and memory.

Specifically, the mamillary bodies receive nervous impulses from the amygdala, related to the regulation of hormonal levels and with the intense emotional responses , and the hippocampus, which as we have seen is a kind of directory of memories that are stored in other parts of the brain.

Specifically, the hippocampus works with memories belonging to the declarative memory, while the amygdala manages the emotional memory, that is, the emotional frame of the memories.

On the other hand, the mamillary bodies send information to the thalamus , the largest brain structure of the diencephalon, responsible for integrating sensory information and generating immediate responses to certain stimuli.

But this should not be interpreted as a sign that the mamillary bodies make "bridges between the hippocampus and the amygdala on one side and the thalamus on the other.

This would occur if the mammillary bodies were simply a stretch of white matter, that is, a part of the brain composed simply of neuronal axons (the long part of these nerve cells, ordered to send nerve impulses to distant areas), but remember that the composition of these is based on the neuronal nuclei, that is, gray matter, areas in which the neuronal somas pile up and they are in almost direct contact with each other.

Thus, the mammillary bodies do not have a passive role in the brain, they do not limit themselves to sending nervous signals to other areas, but they process that information and transform it into something else, even if it is only something slightly different and that is destined to be mixed with the tangle of nervous signals that ascend to the upper part of the brain.

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What is your function?

At the moment little is known about the exact function of mamillary bodies, among other things because they are so small that it is difficult to isolate their processes from others that are inscribed in the overall functioning of the trigone. You only know the generic role that has by connecting involved areas with emotion and memory with the thalamus , which in turn is one of the most complex structures of our nervous system (for example, it has been attributed the function of being the "button" that ignites consciousness).

Therefore, it is necessary to continue investigating to know exactly what is the function of these tiny sets of neuronal nuclei and to take into account that, perhaps, it is more useful to consider it not as an isolated thing but as part of a broader process carried out by the trine or even by the joint action of this and other parts of the brain.

Associated brain injuries, and their effects

It has been seen that lesions in the mammillary bodies are often associated with Wernicke-Korsakoff syndrome.

As suggested by the connectivity of the mammillary bodies, memory problems are among the most prominent symptoms of this syndrome. Specifically, anterograde amnesia stands out, for which it is not possible or is very difficult to create new memories from what is lived in the present.

Thus, the clinical cases of patients with this type of lesion suggest that the mammillary bodies are very involved in memory. However, this region is also especially damaged in other diseases, such as Alzheimer's or schizophrenia .

The fact that each of these neurological or psychiatric conditions has a very wide range of symptoms and that it is not known whether a symptom is due specifically to damage to the mammillary bodies or to injuries in other parts of the central nervous system means that it is clear what is the concrete function of this set of cerebral structures.

2-Minute Neuroscience: Limbic System (November 2022).

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