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The hippocampus is the part of the brain that is primarily responsible for long-term and spatial memory. The hippocampus was discovered a long time ago, and yet this structure is still of interest to scientists - this is due to the fact that more and more connections are found between the hippocampus and its functioning and various diseases, such as Alzheimer's disease, epilepsy and depression. Learn about the functions of the hippocampus and the consequences of its damage.

The hippocampusis part of the limbic system, considered part of the brain and responsible for memory and emotional processes. There are two hippocampuses in humans, one located in the right and the other in the left temporal lobe of the brain. The name of this part of the brain comes from its shape. The hippocampus - at least according to some - resembles a sea horse, and in Greek "hippos" means a horse, while "kampos" is a sea creature.

Medics started discussing the hippocampus quite a long time ago - the first descriptions of this structure of the brain come from 1587, their author was Julius Caesar Aranzi, a Venetian anatomist. For many centuries, up to the present day, this structure has interested many scientists who have devoted a lot of research to the hippocampus. Such interest resulted both from the functions of the hippocampus, but also from the human will to learn - thanks to the study of this structure, many interesting conclusions about the functioning of the nervous system were discovered.

Hippocampus: functions

The hippocampus is mainly responsible for declarative memory (concerning various events and situations), as well as for spatial memory - we owe it to him that we remember the way home, to work or to our favorite restaurant. Information that reaches the brain is initially stored within the so-called short-term memory. The hippocampus is considered to be a structure that processes information within short-term memory and which can "place" it in long-term memory, leading to the occurrence of various memories and our acquisition of knowledge.

The hippocampus is primarily responsible for the possibility of accumulating various memories - it plays a role in the phenomena related tothe functioning of long-term memory.

For many years, the hippocampus was an extremely mysterious structure for researchers. For this reason, numerous studies on the function of the hippocampus have been conducted, but most probably the most important were those works that were possible to perform thanks to a young American patient. This person was Henry Molaison, who struggled with a refractory form of epilepsy. He decided to use a radical therapeutic method, i.e. a neurosurgery during which part of his brain was to be removed. The procedure was actually performed, part of the patient's nervous tissue was resected, which was considered an epileptic focus - parts of Molaison's hippocampus were among the removed tissue.

The patient's operation could be considered successful, but only partially. It turned out that after it, the patient's epilepsy was really under control, his intelligence remained at the level before the surgery, but he developed significant memory problems. After surgery, the patient had essentially no memories of any past events, and was experiencing problems with forming new memories. They were so significant that, when talking to a man, Molaison might have forgotten who he was discussing with even when he merely turned his head away from his interlocutor for a moment.

The disorders that occurred in the above-mentioned patient allowed not only to discover the functions of the hippocampus, but also contributed a lot to the general understanding of the processes related to human long-term memory.

The hippocampus: a structure of the nervous system with unique properties

The hippocampus is one of the most interesting parts of the nervous system not only because of the great role it plays in processes related to human memory. For many years, the medical world believed that the development of nervous tissue - primarily the multiplication of nerve cells - occurs only in the intrauterine period and that later, in life, there is no possibility of new neurons being formed in humans (this would be responsible for treating various diseases neurological as extremely dangerous entities - nerve cells damaged as a result of disease could not be replaced in any way with new neurons).

Along with the constantly developing research possibilities and the progress of medicine, it turned out that the previous observations of the researchers were not entirely true. It has been discovered that in certain regions of the brain new nerve cells may be formed during life. One of the structureswith such possibilities is the hippocampus.

Hippocampus: what can damage it?

Damage to this structure can be caused by processes that are generally unfavorable for the entire brain - we are talking about ischemia or hypoxia, but also about injuries or various infectious diseases, such as encephalitis.

Stress is also suspected of the possibility of damaging the hippocampus, especially stress that is experienced over an extended period of time. Such a conclusion was made on the basis of observations of patients with Cushing's syndrome, i.e. a unit in which the patient's body develops an excess of cortisol. This hormone - especially in excessive amounts - stimulates the so-called the stress axis (composed of the hypothalamus, pituitary and adrenal glands). In turn, scientists were able to observe that in patients with hypercortisolemia there may be a reduction in the size of the hippocampus.

The hippocampus can actually be damaged in many different pathologies.

There are, however, several disease entities that are in a special way related to the hippocampus itself. Among them, we can mention, for example, Alzheimer's disease - in patients suffering from it, a reduction in the size of the hippocampus is sometimes observed. A similar phenomenon is observed in people who are depressed. Various types of hippocampal disorders are also associated with schizophrenia and epilepsy, and it is also suspected that the hippocampus and its dysfunction are associated with the occurrence of transient global amnesia. In the case of these diseases, the direction of the relationships found is not fully known at the moment - for example, in epilepsy it is not clear whether epilepsy itself leads to damage to the hippocampus, or whether it is the dysfunction of the hippocampus that may be the causes of epilepsy. In order to unequivocally determine this type of dependency, it is necessary to carry out many different studies.

Important

Hippocampus: effects of damage to this part of the brain

Looking at the functions of the hippocampus, it is quite easy to guess what damage and dysfunction of this structure are causing. First of all - memory disorders. These include both recreating memories from the past and creating new ones. Patients with hippocampal dysfunction may therefore have incredible problems with the assimilation of new knowledge and with learning - after all, it is the accumulation of information in long-term memory that allows us to learn new languages ​​or remember reading books.

The problem with hippocampal lesions is that they are essentially notcurrently available treatments for them. Patients may be offered various memory training and exercises to improve their cognitive function, although therapies aimed at improving the function of the hippocampus itself do not exist at the moment.

Sources:

1. Hippocampus, Encyclopaedia Britannica materials, on-line access: https://www.britannica.com/science/hippocampus

2. K.S. Anand, V. Dhikav, Hippocampus in he alth and disease: An overview, Ann Indian Acad Neurol. 2012 Oct-Dec; 15 (4): 239-246; on-line access: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3548359/

About the authorBow. Tomasz NęckiA graduate of medicine at the Medical University of Poznań. An admirer of the Polish sea (most willingly strolling along its shores with headphones in his ears), cats and books. In working with patients, he focuses on always listening to them and spending as much time as they need.

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Psychiatry