The human brain is made up of different structures connected to each other and in turn made up of other smaller subdivisions that, through the connections between them, give rise to basic psychological processes and more complex functions. These functions help us function on a daily basis, as they give us the ability to memorize, speak and write, as well as intervene in the processes of attention, perception, learning and thinking.
Currently there are structures whose exact functions and real involvement in the brain we do not know, so we must continue exploring to continue discovering new structures, or learn more about those already discovered. The mammillary bodies, which you may not have heard of before, are a part of this complex network that we have in our heads and are involved in some of the processes that we continually carry out. Do you want to know where they are? What exactly are they and what do they do? In this Psychology-Online article we will talk about the mammillary bodies: what they are, location and functions.
What are the mammillary bodies?
The mammillary bodies are one of the parts that make up the Papez circuit. This set of nervous structures works through two circuits, efferent and afferent. Let’s see how they work:
- The mammillary bodies send output through the mammillo-thalamic bundle to the anterior nuclei of the .
- The anterior nuclei of the thalamus, in turn, connect with certain divisions of .
- The cerebral cortex sends projections to the hippocampal formation back through the entorhinal area.
- At the level of afferents, it sends half of its projections, through the fornix, to the mammillary bodies; also receiving afferents from the medial prefrontal cortex.
Furthermore, it should be noted that the mammillary bodies are anatomically related to brainstem structureswith the septal nuclei, other hypothalamic nuclei and with the nucleus of Broca’s diagonal band.
Location of the mammillary bodies
The mammillary bodies are located in the limbic system. Next, we detail the structures that we must identify to locate the mammillary bodies:
- In the front part of the brain, we have .
- In the most ventral part of the diencephalon we find the hypothalamus, specifically in the anterior part of the thalamus, forming the floor of the third ventricle.
- Within this structure, we find several nuclei and fibers, as part of the gray matter of the brain, which we call mammillary bodies.
What are the mammillary bodies?
If you wonder how many mammillary bodies there are, you should know that it is a complex located in the brain and is made up of 3 cores mostly. The name of these nuclei of this hypothalamic region are:
- Medial mammillary nucleus: constitutes the mammillary bodies, together with the lateral mammillary nucleus.
- Lateral mammillary nucleus: constitutes the mammillary bodies, together with the medial mammillary nucleus.
- Supramammillary nucleus (located dorsal to the two previous nuclei): studies show its importance in the execution of spatial tasks and declarative memory. It is the one with the most information and it knows that it can modulate in two different ways: the supramammillary-hippocampus route and the supramammillary-medial septum route.
Various studies show the connections of the mammillary and supramammillary bodies with the hippocampus, both directly and indirectly, through the septal area. Despite this information, more studies are required to determine what their most notable characteristics are and whether they are involved in other neuronal processes.
Functions of the mammillary bodies
Currently, little is known about the specific functions of the mammillary bodies. As part of the hypothalamus, the main known functions of the mammillary bodies are:
- Princel control center of the vegetative nervous system and the endocrine system.
- Control motivated behaviors such as food and water intake, sexual behavior, etc. Thus, they are key in the control of homeostasis.
- Coordinate physical responses linked to emotional changes. Today’s studies demonstrate the link of connections of those areas involved with emotion and memory, that is, with the thalamus.
Despite this, his involvement in memory processes is reflected in the appearance of brain alterations such as Korsakoff syndromea diencephalic amnesia that occurs due to involvement of the mammillary bodies of the hypothalamus and the dorsomedial nucleus of the thalamus, as a consequence of a thiamine deficiency.
The best known aspect of the mammillary bodies is the pathways with which it connects. We know that are part ofat least, four brain circuits involved in different functions, such as memory. Specifically, some studies have shown its involvement in spatial memory.
What happens if the mammillary bodies are injured
Clinical studies carried out in humans, through neuroimaging techniques, show that the morphological alteration limited to the mammillary bodies, due to different pathological processes, is sufficient to induce severe and persistent alterations in declarative memory. Specifically, they show that these alterations are related to the inability of individuals to form new memories, of variable duration, from the moment of injury.
This article is merely informative, at Psychology-Online we do not have the power to make a diagnosis or recommend a treatment. We invite you to go to a psychologist to treat your particular case.
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Bibliography
- Aranda, L., (2016). Involvement of the mammillary region in spatial learning. Mexican Journal of Psychology, 33(1), 41-49.
- Carlson, N. R. (2014). Physiology of behavior. Madrid. Pearson Education, S.A.
- Portell, I. (2015). Diencephalon. Autonomous University of Barcelona.
- Santín, LJ, Rubio, S., Cimadevila, JM, Begega, A., & Arias, JL, (1997). Spatial memory and mammillary bodies. Psychology writings. 1 (1), 70-81.