What is the cerebellum, what parts make it up and what function does it have?

The cerebellum is a structure that makes up 10% of the total volume of the brain, approximately. He is specialized in the control of movements, sensorimotor integrations and body balance. This part of the brain is located under the cerebral hemispheres, enveloping the brain stem on its dorsal side.

What joins the cerebellum to the rest of the brain are three tracts called cerebellar peduncles. It has multiple connections with different parts of the cerebral cortex that send information about body movements. Together with the basal ganglia, it interacts with the sensorimotor system, coordinating and modulating its activity.

In short, the cerebellum is responsible for regulating movement and posture, adjusting the outputs of the main motor systems. Its function is very important, and its injury can cause very important and disabling deficits in movement, balance and learning motor sequences.

Leonardo da Vinci and the term “cerebellum”

Something that not everyone knows is that one of the first precursors of neuroscience was Leonardo Da Vinci. Passionate as anyone about human physiology, he was the one who actually coined the term “cerebellum.” We are in the year 1504 and da Vinci spends a large part of his nights immersed in a very specific task: making wax molds of the human brain and that area he called the cerebellum, that is, the “small brain.”

His attention was drawn to its two small hemispheres embedded in the brain itself and already in those days, he undoubtedly wondered what function that structure would have. Today, we already know a large number of data about this area, and in fact, it is one of the structures that most intrigues neurologists.

In fact, it is enough to just advance one piece of information: eThe cerebellum only has 10% of brain volume but in reality, it contains almost 80% of the total neurons in our brain. Has your curiosity been piqued?

Structure of the cerebellum

To this day we still do not know all the functions of the cerebellum. However, what we do know clearly is how it is made up. The cerebellar surface can be classified into three different parts: two hemispheres and vermis. Regarding its organization, The cerebellum has 3 layers:

The granular layer. It is the most internal and is made up of a large number of interneurons (granular and Golgi).The molecular. It is where the axons of the granule cells are located. There are also interneurons, but different ones (stellate and basket).Purkinje cell. It is located between the two previous layers and is formed by the bodies of Purkinje cells, the only projection cells of the cerebellar cortex. Its axons go to the deep nuclei of the cerebellum.

As for the deep nuclei, inside the white matter we can find 4 pairs of gray matter nuclei. They are the following:

Toothed core. The cerebellum sends the result of the analysis of information from the motor cortex about the onset of movement. It is involved in learning new motor patterns.Interposed nuclei (emboliform and globose). It is responsible for the movement of arms and hands (rubrospinal system). Also learning new motor patterns.Fastigial or roof core. It deals with balance and automatic functions of movement.pontine nucleus. It communicates the frontal association cortex and the primary motor cortex with the lateral area of ​​the cerebellum.

Main functions of the cerebellum

The cerebellum is responsible for controlling both motor functions, coordination and balance. Now, these are tasks that have been known for decades, just as we know that they are key in motor learning. Likewise, this structure carries out very sophisticated tasks.

One of them is the neural programs for the control of learned movements. Thanks to it we carry out automatic actions, such as driving a car. Let’s see, however, what other functions it performs.

The cerebellum and emotions

The cerebellum is connected to the limbic system and the cerebral amygdala.. Thanks to this union point, we can regulate our emotions, associate sensations with feelings, and learn from these processes in turn.

Regulate our thoughts

In 2016, an interesting article was published in the Journal of Neurology where Dr. Jeremy D. Schmahmann, from Harvard Medical School and director of the ataxia unit at Massachusetts General Hospital, revealed something shocking. The cerebellum is key in our cognitive processes.

He developed this theory after his extensive clinical practice. He could see how Patients with damage to the cerebellum presented deficits in the cognitive domains of executive function, spatial cognition, and language.

The cerebellum and movement

The cerebellum has connections with different parts of the central nervous system, thanks to which it carries out multiple functions. The best known are these:

Vestibulo-cerebellar. It sends corrective signals to the vestibular nuclei to modify posture and restore balance. Damage to this pathway can cause instability and nystagmus (small, rapid eye movements).Spino-cerebellar. It intervenes in the control of posture and locomotion and modifies muscle tone. Controls limb movements. An injury to this pathway would cause an ataxic gait (wobble and sway when walking).Cerebro-cerebellar. Modulator of the descending systems of the cerebral cortex. It is key to the coordination of voluntary movements. It is involved in the initiation of movements. An injury to this connection would cause movements to take longer to start and finish.

In the different connections of the cerebellum with the rest of the areas, it almost always acts as a regulator. Records information and regulates the movements of different parts of the body, depending on the structure to which it is connected. Functions such as maintaining balance or learning a movement could be made more difficult if these pathways are disrupted.

Cerebellum and working memory

Cerebro-cerebellar connections are also involved in performance on working memory tasks. As can be seen in the following study, in a resting state, the neural basis underlying memory processing is directly related to these connections between the brain and cerebellum.

Processing and error correction

Although the hypothesis that the cerebellum constitutes a system in itself due to the influence it has on the detection and correction of errors in one’s own behavior must be reviewed, the truth is that these processes are closely linked. In this way, it is known that Purkinje cells are activated when dealing with highly complex environments, forming neural systems that favor the creation of long-term cognitive models.

Cerebellum and reward circuits

We continue with the controversy of whether the cerebellum has anything to say in cognitive function. In this sense, the cerebellum plays a fundamental role in shaping cognitive processing and they suggest that the cerebellum can combine both supervised learning and reinforcement learning to optimize goal-directed action. According to this study, the expectation of reward, as well as its delivery, its size and its omission, can be encoded in the cerebellar cortex.

What happens when the cerebellum is injured?

When the cerebellum is injured, some of its functions can be compromised and cause motor problems. A loss of ability to accurately control steering may occur.the strength, speed and amplitude of movements, as well as the ability to adapt movement patterns outputs to the change of conditions.

Organ injury can lead to two different symptomatic syndromes: the vermian syndrome (archicerebellar) with alterations in statics and gait, and the hemispheric cerebellar syndrome (neocerebellar) with alterations in the coordination of movement. The lesion of the afferent pathways produces an archicerebellar syndrome, and that of the efferent pathways is manifested by a neocerebellar syndrome.

A person with a cerebellar lesion may find it difficult to maintain a seasonal posture (stand) and the act of trying gives way to tremors. It is also common to detect abnormalities in balance, gait, speech and even the control of eye movements. Therefore, movements of all kinds can be affected. Those who suffer from it find it difficult to learn new motor sequences.

Pathologies that produce cerebellar degeneration

Some neurological diseases can cause neuronal death in the cerebellum. In this way, cerebellar degeneration can favor the following conditions:

Multiple sclerosisin which damage to myelin can affect the cerebellum.Transmissible spongiform encephalopathies. Like, for example, mad cow disease. Abnormal proteins cause inflammation of the brain, especially the cerebellum.Friedreich’s ataxia. Caused by hereditary genetic mutations that progressively kill neurons in the cerebellum, brainstem, and spinal cord.endocrine diseases that affect the thyroid or pituitary glandChronic alcohol abuse that causes temporary or chronic cerebellar damage.

The most characteristic symptoms of cerebellar degeneration are a staggering and unstable gait with the legs apart, usually accompanied by a swaying of the trunk, forward and backward. Other symptoms include slow, unsteady, jerky movements of the arms and legs, slow, slurred speech, and nystagmus (small, rapid eye movements).

Cerebellar degeneration is often a consequence of inherited genetic mutations that alter the normal production of specific proteins necessary for the survival of neurons. Cerebellar disorders are rare, but their impact can be very harmful and seriously affect the quality of life of people who suffer from it.

Treatments for conditions in the cerebellum

Some systemic disorders (such as hypothyroidism or celiac disease) and exposure to toxins can be treated, The intervention in these cases will depend on the causes. For its part, in injuries…