Hippocampal formation: parts and functions of this area of the brain.

This brain structure is related to memory and orientation.

How are our memories formed? How are we able to remember how to get to our home or place of work? These functions that we carry out unconsciously, without stopping to think about them, are made possible by brain structures such as the thanks to brain structures such as the hippocampal formation..

Throughout the article we will talk about this complex brain structure, the organs that make it up and how scientific research has been developing various theories about its functions.

What is the hippocampal formation?

In neuroanatomy the hippocampal formation refers to a brain structure located in the medial temporal lobe.. Although within the field of research itself there are discrepancies about which specific organs or brain regions form this structure, most agree that at least the dentate gyrus, the hippocampus and the subiculum are included within this classification. However, other areas such as the presubiculum, parasubiculum and entorhinal cortex are subject to discussion, since not all authors recognize them as part of the hippocampal formation.

The main functions of the regions that make up the hippocampal formation are related to memory processes, navigation and spatial orientation, and attention control.

Historical tour

During the 19th and early 20th centuries, research on the hippocampal formation, more specifically the hippocampus, pointed to the idea that it played some kind of role in the olfactory system.

Furthermore, in 1937, research by scientists such as Papez or Klüver and Bucy began to develop the hypothesis that the hippocampal formation played an important role in emotional responses. However, today there is little support for the idea that these structures are directly involved in emotional processes, since emotional memory is more closely related to the amygdala.

Although it was not until centuries later that the relationship between hippocampal structures and memory processes was recognized, in 1900 the Russian-born neurologist Vladimir Bekhterev discovered an association between significant memory deficits and hippocampal and cortical tissue softening. and cortical tissue.

Similarly, in 1957 researchers Scoville and Milner also reported symptoms related to memory loss in patients with medial temporal lobe lesions. These were some of the first investigations thanks to which we now know that the hippocampal formation plays an essential role in some memory processes.

Finally, animal studies conducted in 1970 also established the relationship between the hippocampus and spatial coding. However, this association is still widely debated by the scientific community.

Parts of the hippocampal formation

As indicated at the beginning of the article, the hippocampal formation is composed of the hippocampus and the hippocampus, the hippocampal formation is composed of several brain structures. These structures are the dentate gyrus, hippocampus and subiculum.

1. Dentate gyrus

The dentate gyrus is a part of the hippocampal formation that is attributed an important role in episodic memory. is attributed with an important role in episodic memory, as well as in the exploration of newas well as in the exploration of new environments. In addition to memory formation, the dentate gyrus is also hypothesized to be involved in some way in emotion regulation.

Memory

The dentate gyrus is believed to be one of the few brain regions in which neurogenesis, i.e., the birth of new neurons, takes place. It is also hypothesized that this neurogenesis facilitates or enhances the formation of new memories. enhances the formation of new memoriesas well as being associated with the improvement of spatial memory.

Stress and depression

Other aspects in which the dentate gyrus has a functional role are stress and depression. Some research has shown that neurogenesis is increased in response to Antidepressant treatment, as well as a relationship between the physiological effects of stress and the inhibition of the birth of new neurons.

Finally, it is known that both endogenous glucocorticoids generated as a product of stress can play psychosis and depression, implying that neurogenesis in the dentate gyrus may play an important role in modulation of the symptoms of these emotional responses..

Spatial behavior

Animal studies have shown that after injury or destruction of the cells of the dentate gyrus, extreme difficulty in orienting oneself through a maze occurs. Specifically, problems appear when it comes to consolidating learned information about a specific location.Therefore, it is hypothesized that lesions in the dentate gyrus may cause alterations in spatial memory.

2. Hippocampus

The second and most important organ of the hippocampal formation is the hippocampus, one of the main structures of the mammalian brain, located in the medial or inner part of the temporal lobe. located within the medial or inner part of the temporal lobe..

The main functions of the hippocampus are related both to memory processes and to spatial memory and orientation. Let's see what they are.

Memory

According to general consensus, the hippocampus is responsible for the formation of new memories, both episodic and episodic. the formation of new memories, both episodic and autobiographical.. In addition, an increase in hippocampal activity has been demonstrated in response to novel stimuli.

Lesions in this structure do not usually affect other types of memory formation related to the acquisition of motor or cognitive skills, but they do affect the formation of new memories. In other words, damage or impairment of the hippocampus can lead to the development of anterograde amnesia.

Spatial memory and orientation

As in the dentate gyrus, animal studies have shown that some neurons of the hippocampus generate a series of electrical potentials when the animal moves through specific areas of its environment.

Although the evidence for this activity in primate brains is very limited, this neuronal activity may suggest that the hippocampus also has certain responsibilities in spatial memory and orientation.

3. Subiculum

Finally, the structure known as the subiculum is the lowest part of the hippocampal formation.

Although this structure is still under investigation, it is speculated that the subiculum is involved in some cases of epilepsy. In addition, it has also has also been linked to working memory and spatial orientation, and it is suggested that it may be involved in some cases of epilepsy.It has also been suggested that it may be involved in some processes of drug addiction.