The
hippocampus is one of the most important parts of the brain.

It is located in what is known as
limbic system, and is closely related both to mental processes related to memory and to those that have to do with the production and regulation of emotional states, as well as intervening in spatial navigation, that is, the way we imagine movement through a particular space.

The Anatomy of the Hippocampus

The etymology of the term “hippocampus”, a word coined by the anatomist
Giulio Cesare Aranzio , refers to the similarity between this structure of the brain and a seahorse. It is a small organ with a curved and elongated shape, which is located on the inside of the temporal lobe and goes from the hypothalamus to the amygdala. Therefore, each brain has two hippocampuses: one in each hemisphere of the brain.

In addition, the hippocampus is associated with a part of the cerebral cortex known as the archaicortex, which is one of the most ancestral regions of the human brain; that is, it appeared many millions of years ago in our evolutionary line. That is why the hippocampus is so well connected to other parts of the limbic system, that it appeared to provide answers to some of the most basic needs of our most remote mammal ancestors. In turn, this fact already allows us to intuit that mental processes related to emotions are linked to the functions of the hippocampus. Let’s see what they are.

The functions of the hippocampus

The main function of the hippocampus is to mediate the generation and recovery of memories in conjunction with many areas spread throughout the cortex and other areas of the limbic system.

It therefore has a very important role in consolidating the learning that has taken place, since on the one hand it allows certain information to pass into long-term memory and on the other it links this type of content with certain positive or negative values, depending on whether these memories have been associated with pleasant or painful experiences (physiologically or psychologically).

It is the mental processes linked to emotion that determine whether the value of an experience stored as a memory is positive or negative. What we experience as emotions has a functional part that has to do with the way we learn to behave following some learned rules that play in our favor: avoid repeating mistakes and experiencing pleasant sensations again.

The Hippocampus and Memory

You would think that
the hippocampus is the part of the brain where long-term memories are stored . However, the reality is more complex than this idea.

The relationship between the hippocampus and long-term memories is not as direct:
this organ acts as a mediator, or directory, of memories , the appearance and disappearance of which is associated, as far as is known about the functioning of memory, with the activation and deactivation of networks of neurons distributed over many areas of the brain. In other words, the hippocampus does not “contain” memories, but acts as a trigger node that allows different memories distributed in different parts of the brain to be activated.

In addition, the hippocampus is more related to some types of memory than to others. Specifically,
plays a role in the management of declarative memory , that is, the contents of which can be expressed verbally; however, non-declarative memory, which intervenes in the memorization of movement patterns and motor skills (such as dancing or cycling), is regulated rather by structures such as the basal ganglia and the cerebellum.

It is known that a lesion in this area of the brain usually produces
anterograde and retrograde amnesia in the production and evocation of memories related to declarative memory, but non-declarative memory is usually preserved. A person with a severely damaged hippocampus may continue to learn, for example, manual skills (although he or she would not remember learning this process).

The hippocampus in space travel

From what is known about the hippocampus,
this brain structure also seems to intervene in the way we perceive space , that is, the way we keep in mind a three-dimensional space through which we move, taking into account its volumes and references.

In fact, within the hippocampus a type of neurons called place cells have been discovered, which you can read more about in
this article.

The hippocampus under disease

The region of the hippocampal formation is one of the first areas where diseases such as
dementia or Alzheimer’s . That is why people who start to experience this disease see their ability to form new memories or remember more or less recent autobiographical information diminished.

However, even if the hippocampus is badly damaged,
usually the oldest and most relevant memories about the person’s life take a long time to disappear , which could mean that over time the oldest and most relevant memories become increasingly “independent” of the hippocampus.

Bibliographic references:

  • López-Pousa S., Vilalta Franch J., Llinàs Reglà J. (2002). Manual de Demencias, 2nd Edition. Prous Science, Barcelona.
  • Martínez Lage J.M., Láinez Andrés J.M. (2000). El Alzheimer: teoría y práctica. Aula médica ediciones, Madrid.