Seahorse brain. Orientation in space and the hippocampus

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Hippocampus. Have you ever felt stupid, forgetting at the last moment what you wanted to say? Our head is full of various information that we accumulate over the years. Sometimes there is so much information that our brain is forced to forget or ignore some part of it.

The region of the brain responsible for such essential functions as memory, emotion, and learning is called the hippocampus. Without it, we would lose the ability to remember and experience the emotions associated with those memories. Want to know more? Neuropsychologist Mairena Vasquez will tell you about what the hippocampus is and why such a tiny brain structure is so important.

The hippocampus is responsible for memory and emotions.

What is a hippocampus?

The hippocampus owes its name to the anatomist Giulio Cesare Aranzio, also known as Arantius or Julius Caesar Arantzi, who, as early as the 16th century, drew attention to the fact that this part of the brain is outwardly very similar to a seahorse. The word "hippocampus" comes from the Greek Hippos (horse) and Kampe (curved).

Having done scientific discovery of this brain structure, Arantius associated it with the sense of smell, putting forward the idea that the main function of the hippocampus is the processing of olfactory stimuli (smells). This theory was supported until 1890 - until Academician Vladimir Bekhterev proved that in reality the hippocampus is responsible for memory and cognitive processes.

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The hippocampus is one of the most important parts of the human brain, closely associated with memory and emotions. It is located in temporal lobe(behind each temple) and communicates with various parts of the cerebral cortex.

hippocampus counts basic memory structure.

This is a small paired organ of an elongated and sinuous shape, located in both hemispheres of the brain (i.e. one hippocampus in the right and left hemispheres).

The hippocampus got its name from its resemblance to a seahorse.

Where is the hippocampus located?

The hippocampus is located in medial temporal lobe and connected to various areas brain.

The hippocampus, as well as the amygdala, both form and are responsible for controlling primitive physiological reactions. These regions belong to the most "ancient, deep and primitive" part of the brain, known as the "archicortex" ( old bark) or "allocortex" (most ancient area human brain), which appeared millions of years ago to provide the basic needs of the ancestors of mammals.

The hippocampus is located in the temporal lobe and is part of the limbic system. Rice. Wikipedia

Why is the hippocampus needed?

What are the functions of the hippocampus? What role does he play? What is he responsible for? Among the main functions hippocampus - mental processes associated with memory consolidation and process learning, as well as the processes of occurrence and regulation emotional states and providing orientation in space.

A number of researchers have also found an association of the hippocampus with inhibition or inhibitory control of behavior, but this is fairly new information that is still being studied.

The hippocampus and memory

The hippocampus is primarily responsible for the emotional and declarative memory. With it, we can recognize faces, describe objects and events, and associate positive or negative experiences and sensations with memories of lived events.

The hippocampus is involved in formation of both episodic and autobiographical memories based on our past experience. The brain needs a place to store all this information for many years, so the hippocampus transfers these temporary memories to other areas of the brain, where they are stored in long-term memory.

That is why the oldest memories are better preserved. If the hippocampus is damaged, we would lose the ability to learn and retain information in memory. In addition to the ability to turn memories into long-term memory, the hippocampus associates their contents with positive or negative emotions, depending on whether these memories are associated with positive or negative experiences.

There are many types of memory: episodic memory, procedural memory, implicit or hidden memory, declarative memory, etc. The hippocampus is responsible for declarative memory(includes our personal experience and knowledge about the surrounding world), managing its content, which can be expressed in verbal form (words). Different kinds memory is not exclusively regulated by the hippocampus, other parts of the brain are also involved. The hippocampus is responsible for most processes associated with memory loss, however, not for all.

The hippocampus and learning

The hippocampus is one of the few areas of the brain capable of neurogenesis throughout life, in connection with which he is responsible for learning and retention of information. In other words, the hippocampus is able to create new neurons and connections between them throughout the life cycle.

Knowledge is acquired gradually after many efforts, and this is directly related to the hippocampus. For the storage of new information in our brain, the formation of new neural connections is vital. Therefore, the hippocampus plays a major role in learning.

Curious fact: is it true that the hippocampus of London taxi drivers is larger and better developed? Why? To get a license, London taxi drivers must pass a difficult exam, for which they must learn by heart great amount streets and places. In 2000, Eleanor Magire conducted a study of London taxi drivers which showed that rear end their hippocampus is larger. She also found that the size of the hippocampus is directly proportional to the driver's work experience. In this way, training, learning and experience change and shape the brain.

Effects of learning on the brain and hippocampus in London taxi drivers. Rice. frontiersin.org

Orientation in space and the hippocampus

One of the important functions in which the hippocampus plays a significant role is spatial orientation.

Spatial orientation or navigation allows us to keep our mind and body in three-dimensional space, move and interact with the outside world.

There have been various rodent studies that have shown that the most important function of the hippocampus is the ability to navigate and spatial memory. Thanks to the hippocampus, we can navigate in unfamiliar cities and areas, etc. However, these data have not yet been studied in humans and require further research.

What happens when the hippocampus is damaged?

Damage to the hippocampus leads to the inability to remember new events. Those. anterograde amnesia occurs, in which a person cannot remember events that occurred after the memory impairment. At the same time, knowledge and memory of what happened before the onset of the disease are preserved.

Hippocampal lesions can cause anterograde or retrograde amnesia, depending on the loss of memories associated with declarative memory. In this case, non-declarative memory is not affected and remains intact. For example, a person with hippocampal disease may learn to ride a bicycle after the onset of the disease, but will not remember ever seeing a bicycle before in their life. Those. a person with a damaged hippocampus is able to acquire skills, but cannot remember the process itself.

Anterograde amnesia is the loss of memory for events that occurred after the onset of an illness or injury. Retrograde amnesia, on the contrary, leads to forgetting the events and memories that preceded the illness or injury.

The question arises: why is the hippocampus damaged during amnesia? explaining in simple words, this part of the brain is like a doorway for neural patterns that sporadically hold information in before it reaches the frontal lobe. It can be said that the hippocampus is the key to memory consolidation, turning Short Term Memory into Long Term Memory. If this door is damaged and does not allow information to be stored, it will be impossible to create long-term memories.

In addition, when the hippocampus is damaged, not only the ability to remember is lost, but the ability to experience the emotions associated with these memories, since the person cannot connect the events and the feelings that they caused.

What causes damage to the hippocampus?

Most hippocampal lesions are due to aging and stress, cerebrovascular disease, epilepsy, aneurysm, encephalitis, schizophrenia, etc.

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Aging and dementia

In aging in general and dementias (such as Alzheimer's) in particular, the hippocampus is one of the most vulnerable parts of the brain. The ability to form new memories or recreate fresh autobiographical facts is impaired. AT this case The cause of memory problems is the death of neurons in the hippocampus.

Most of us have come across people with some form of dementia or memory loss. Curiously, such people retain childhood memories or memories of very old events the longest. Why does this happen if the hippocampus is damaged?

The fact is that even with severe damage to the hippocampus(due to dementia or other disease) the oldest and most important memories for a person are best preserved because of over time these memories, as we mentioned above, "separated" from the hippocampus, becoming part of other brain structures associated with long-term memory.

The hippocampus and stress

This part of the brain suffers greatly under stress, as stress inhibits and atrophies neurons.

Have you noticed that in a state of stress, when you need to do a lot of different things, sometimes you start

stress, and in particular cortisol(a type of hormone released in response to stress) damages our brain structures, often causing neuronal death. Therefore, it is very important to learn how to remain calm and manage your emotions in order to keep the hippocampus healthy and help it perform its functions optimally.

To learn more…

If you are interested in this topic, watch the film "Remember" ("Memento"), in which main character, suffering from anterograde amnesia, tirelessly tries not to forget everything that happens to him.

We will be grateful for questions and comments on the article.

Translated from Spanish by Anna Inozemtseva French

Hippocampal sclerosis is one of the forms of epilepsy, the cause of which is the pathology of the parts of the limbic system of the brain. The main generator of epileptic activity is gliosis in combination with atrophy of the cortical plate of the underlying white matter. To diagnose the disease, neurologists at the Yusupov hospital use modern methods instrumental research, perform laboratory tests and minimally invasive diagnostic procedures.

Sclerosis of the hippocampus is accompanied by loss of neurons and scarring of the deepest part of the temporal lobe. Often caused by severe brain injury. It is left handed and right handed. Brain damage due to trauma, neoplasm, infection, lack of oxygen, or uncontrolled spontaneous seizures leads to the formation of scar tissue in the hippocampus. It begins to atrophy, neurons die and form scar tissue.

Based on structural changes, two main types of temporal lobe epilepsy are distinguished:

with the presence of a volumetric process (tumor, congenital pathology, aneurysm of a blood vessel, hemorrhage) affecting the limbic system;
without the presence of clearly verified volumetric changes in the area of the medial temporal lobe.

Causes of bilateral sclerosis of the hippocampus

The following causes of hippocampal sclerosis are known:

hereditary predisposition;
hypoxia of brain tissue;
brain injury;
infections.

Today, the following theories of the development of hippocampal sclerosis are considered the main ones:

the influence of febrile convulsions leading to regional metabolic disorders and edema of the temporal lobe cortex. Neuronal death occurs, local gliosis and atrophy develop, as a result of which the volume of the hippocampus decreases, reactive expansion of the sulcus and the lower horn of the lateral ventricle.
acute circulatory disorders in the basin of the terminal and lateral branches of the posterior cerebral artery cause basal ischemia of the temporal lobe, secondary diapedetic sweating, neuronal death, gliosis and atrophy occur.
violation of the development of the temporal lobe during embryogenesis.

Symptoms of hippocampal sclerosis

Sclerosis of the hippocampus usually leads to focal epilepsy. Epileptic seizures appear in groups or individually. They are complex, starting with strange indescribable sensations, hallucinations or illusions, followed by a numb gaze, food and rotational automatisms. They last about two minutes. With progression, generalized tonic-clonic seizures may occur.

Attacks with sclerosis of the hippocampus may be accompanied by various symptoms:

behavior change;
memory loss;
headaches;
increased anxiety;
sleep problems;
panic attacks.

Patients develop impaired cognitive abilities (memory, thinking, ability to concentrate). Seizures that disrupt brain activity can lead to sudden loss of consciousness, as well as autonomic cardiac dysfunction. Patients with left-sided hippocampal sclerosis have more severe parasympathetic dysfunction compared to patients with right-sided mesial sclerosis.

Epilepsy attacks are accompanied by auditory or vestibular hallucinations, belching or autonomic manifestations, paresthesias, and unilateral facial twitching. Patients note the difficulty of learning, memory impairment. They are conflicted, emotionally labile, have an increased sense of duty.

To diagnose the disease, the doctors of the Yusupov hospital use the following examination methods:

neuroradiological diagnostics;
computed tomography;
nuclear magnetic resonance spectroscopy;
angiography;
electroencephalography.

The study is performed on modern equipment from leading world manufacturers.

Treatment of hippocampal sclerosis

To reduce the symptoms of the disease, neurologists at the Yusupov hospital prescribe antiepileptic drugs. The first choice is carbamazepine. Second choice drugs include Valproate, Difenin, and Hexamidin. After treatment, some patients stop having seizures, and a long-term remission occurs.

With resistance to ongoing therapy and progression of hippocampal sclerosis, surgical treatment is performed in partner clinics. It consists in removing the temporal lobe of the brain (lobectomy). After surgery, in 70-95% of cases, the number of seizures decreases. If you are faced with the problem of hippocampal sclerosis and wish to receive a qualified specialized medical care, make a phone call. You will be booked in for a consultation with a neurologist at the Yusupov Hospital.

Bibliography

ICD-10 (International Classification of Diseases)
Yusupov hospital
Gusev E.I., Demina T.L. Multiple sclerosis // Consilium Medicum: 2000. - No. 2.
Jeremy Taylor. Darwin Health: Why We Get Sick and How It's Evolution Related = Jeremy Taylor “Body by Darwin: How Evolution Shapes Our Health and Transforms Medicine”. - M.: Alpina Publisher, 2016. - 333 p.
A.N. Boyko, O.O. Favorova // Molecular. biology. 1995. - V.29, No. 4. -p.727-749.

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The hippocampus is a paired structure located in the medial temporal regions of the hemispheres. The right and left hippocampi are connected by commissural nerve fibers running in the commissure of the fornix (commissura fornicis) of the brain.
Hippocampi form the medial walls of the lower horns of the lateral ventricles (lat. ventriculus lateralis) located in the thickness of the hemispheres of the large brain, extend to the most anterior sections of the lower horns of the lateral ventricle and end with thickenings, divided by small grooves into separate tubercles - seahorse toes (lat. digitationes hippocampi). On the medial side, the hippocampal fimbria is fused with the hippocampus (lat. fimbria hippocampi), which is a continuation of the leg fornix of the terminal brain. The choroid plexuses of the lateral ventricles adjoin the fimbriae of the hippocampus.

Functions

The hippocampus belongs to one of the oldest systems of the brain - limbic, which determines its significant versatility. Presumably, the hippocampus secretes and retains in the stream of external stimuli important information, performing the function of short-term memory, and the function of its subsequent transfer to long-term. Most researchers agree that the hippocampus is associated with memory, but its mechanism is not yet clear. There is a theory of "memory of two states" that the hippocampus holds information in wakefulness, and translates it into the cerebral cortex during sleep. Another function of the hippocampus is the memorization and coding of the surrounding space (spatial memory). In this connection, it is activated whenever it is necessary to keep the focus of attention on external guidelines that determine the vector of behavior.
When the hippocampus is damaged, the Korsakov syndrome occurs - a disease in which the patient, with a comparative preservation of traces of long-term memory, loses memory for current events.
A decrease in the volume of the hippocampus is one of the early diagnostic signs in Alzheimer's disease.
One of the functions of the hippocampus is to forget information. This is because the hippocampus filters information and chooses what to keep and what to forget.
According to the results of studies by Kirsty Spalden, Jonas Friesen and others, it turned out that the rate of formation of new neurons in the hippocampus for an adult is estimated at 1400 neurons daily, which corresponds to 1.75% of the part of the hippocampus that is updated during the year (based on its average volume of 30 million neurons).

Role in spatial memory and orientation

Conducted studies, including recent ones, show that the hippocampus is used to store and process spatial information. Studies on rats have shown that the hippocampus has neurons (neurons places) that perform the function of memory about places in space. On these neurons are projected neurons located in the entorhinal cortex of the direction of the head, neurons of the grid, neurons of the border and neurons of the speed. Together, these neurons provide orientation in space. Place neurons and grid neurons fire when an animal finds itself in a certain place, regardless of the direction of movement, velocity neurons and head direction neurons are sensitive to movement speed and head position.
In rats, certain neurons, called context-dependent, can fire depending on the animal's past (retrospective) or expected future (perspective). Different neurons fire from different locations of the animal, so that by observing the potential of individual neurons, one can tell where the animal is in one's own opinion. As it turned out, the same spatial neurons in humans are involved in finding a way while navigating through virtual cities. Such results were obtained through the study of people with electrodes implanted in the brain, used for diagnostic purposes for surgical treatment severe epileptic seizures.
The discovery of spatial neurons led to the idea that the hippocampus could play the role of a map - a neural representation of the environment and the location of the animal in it. Studies have shown that the hippocampus is essential for solving even the simplest tasks that require spatial memory (for example, finding a way to a hidden goal). Without a fully functioning hippocampus, people may not remember where they have been or how to get to their destination; disorientation is one of the most common symptoms of amnesia. Brain imaging shows that the hippocampus is most active in humans during successful movement through space, as in the virtual reality example.
There is also evidence that the hippocampus plays a role in finding shortcuts between already well famous places. For example, taxi drivers from London need to know a large number of places and the shortest paths between them. A study from a London university in 2003 showed that the hippocampus of taxi drivers is larger than that of most people, and that the most experienced taxi drivers have a larger hippocampus. Whether an initially larger hippocampus helps to become a taxi driver, or whether the constant search for the shortest path leads to its growth has not yet been clarified. Be that as it may, during a study of the correlation between gray matter size and time spent as a taxi driver, it was found that than more people works as a taxi driver, the larger the volume of the right side of the hippocampus. It was found that the total volume of the hippocampus remains unchanged in both the control group and taxi drivers. In short, the back of the taxi drivers' hippocampus did get bigger, but at the expense of the front.

responsible for the consolidation of memories when they move from short-term memory to long-term memory, as well as for the creation of emotions and spatial orientation. The human brain has two hippocampi located in the temporal parts of the hemispheres. The connection between them is maintained with the help of nerve fibers that run in the commissure of the fornix of the brain.

Functions

In the past, scientists have put forward the version that the hippocampus is responsible only for the sense of smell. But Scientific research held modern specialists, proved its important role in the formation of orientation in space, perception and storage of information. Some neurons in the hippocampus, called spatial and cells, help a person or animal to determine in space and its location, to find a short path between two landmarks.

The normal operation of the hippocampus is very important in learning, but it is not the ultimate repository of knowledge. That's what the cerebral cortex is for. In the hippocampus, a memory of recent events is formed, and only after a while - hours, days and weeks - this new information is placed in the cerebral cortex. The structure of this body is heterogeneous, and consists of several specialized departments. Thanks to this, the hippocampus is able to instantly remember various events, but sometimes, in order for this to happen, it is necessary to repeat a particular situation that a person has already encountered.

Biased Decisions

Neuropsychologists from the USA explained the mechanism of decision-making by a person in cases of his encounter with unfamiliar circumstances, when it is not possible to rely on previous experience and calculate the final result of getting out of the current situation. In this case, a person associates the situation with cases that have already happened to him and, based on this, draws conclusions. This affects the adoption of certain decisions to get out of the current situation. main role the hippocampus plays a role in making these decisions.

It has already been noted that people who, by the nature of their occupation, often have to deal with memorizing this or that information or finding a way out, for example, mentally plotting a route, have an increase in the hippocampus. In addition, this can be achieved by regular exercises - playing checkers and chess, memorizing poetry or foreign languages, solving crossword puzzles, developing your numerical sense and so on.

Hippocampal damage

In Alzheimer's disease, this organ first of all suffers, which leads to a decrease and loss of memory, disorientation. In addition, damage to the hippocampus can lead to anoxia, encephalitis, or medial temporal lobe epilepsy.

If both hippocampi are damaged, anterograde amnesia can occur, in which a person loses the ability to remember recent events, but his long-term memory does not suffer. He will be able to continue to live, talk, walk, hear - do everything that seems normal and natural, but will not be able to create new memories. That is, the information that he will receive after damage to the hippocampus will seem new to him every time, for example, each visit to the doctor will be like the first for him.

Scientists have proven that the normal functioning of the hippocampus depends on the duration and sleep of a person. A night without rest can affect the memory of information. So, in a person who missed a dream once, the impossibility of perceiving positive words by almost 60% was revealed, while he could not remember negative words by only 19%. From this it follows that the hippocampus of a sleepy person shows little activity.

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