Subcortical structures of the brain: types and functions

We explain how are the nerve cell nuclei that are hidden under the brain surface.

Absolutely each and every one of our motor, social and emotional abilities and skills are governed and coordinated by the various structures that make up the entire brain.

One of these systems are the subcortical structures of the encephalonwhich have functions in the motor system, as well as in the performance of social skills or in the regulation of emotions. Throughout this article we will explain each one of these structures as well as the possible consequences of an injury in them.

What are subcortical structures?

Within the field of neuroanatomy, the structures that make up the nervous system are studied. Some of these systems are those known as subcortical structures.

The subcortical system or structure, located in both cerebral hemispheres, is composed of those brain centers that are located between the white matter, located near the lateral and ventral region of the lateral ventricles..

As complementary information, the white matter is the matter that makes up 60% of the brain. This substance is formed by a large number of nerve fibers, which in turn contain neuronal axons. These axons are characterized by being covered by a myelin sheath that protects them and favors the rapid transmission of electrical nerve signals.

As mentioned above, the subcortical structure is made up of different nuclei, specifically four: the hippocampus, cerebellum, amygdala and basal ganglia, each of them with a specific location and functions, so that in case of injury the person will experience a significant decrease in a range of psychological and mental abilities and skills in general..

Broadly speaking, the main functions in which these brain centers are involved include:

• Regulation of character and emotional responses..
• Regulation of the person's instinctive responses: flight response, hunger, etc.
• Modulation of the visceral and endocrine functions of the organism.
• Regulation of wakefulness and sleep processes.
• Regulation of attention and arousal processes.

Subcortical brain centers

As mentioned above, The subcortical structures are made up of a series of nuclei, each of which has characteristics that distinguish and differentiate it from the other centers.each of which has characteristics that distinguish and differentiate it from the rest of the centers. Below we describe them one by one, as well as their functions and the consequences that may appear if they are damaged.

1. Hippocampus

The hippocampus is one of the main brain structures that can be found both in humans and in other mammalian animals. This small organ located in the medial temporal lobe and with a shape that resembles that of a seahorse (hence the etymological origin of its name), is one of the most important parts of the limbic system..

Traditionally, the limbic system has been associated with the regulation of emotions, whereas the hippocampus has a fundamental role in memory processes, especially in long-term memory.especially in long-term memory, and in spatial navigation.

Lesions in the hippocampus

As mentioned above, this subcortical organ plays a fundamental role in memory processes, so any type of damage or injury to it can cause a significant impairment in memory, especially when it comes to generating new memories..

For example, in Alzheimer's disease, hippocampal damage caused by neurodegeneration is one of the first symptoms to appear, initially causing disorientation and mild memory problems.

2. Cerebellum

This second region belonging to the subcortical structure and known as cerebellum is located in the lower area of the cerebral hemispheres. By means of three conduits known as cerebellar peduncles, the cerebellum remains connected to the rest of the brain, sending information about body movements to the cerebellum..

In addition, its work in collaboration with the basal ganglia (another subcortical structure) makes possible the functioning of the sensorimotor system.

Broadly speaking, the cerebellum has two main functions:

• Development of motor learning and control of acquired movements Development of motor learning and control of acquired movements by creating neural patterns that convert them into mechanized movements.
• Correction of movement errors through feedback.

Cerebellar lesions

In the case of the cerebellum, when it suffers some damage or degeneration, problems in motor functions and skills begin to appear. These problems range from clumsiness in the movements or problems to control with accuracy the direction and speed of these movements, to alterations in coordination, balance and maintenance of a fixed body posture..

Damage to the cerebellum may be caused by diseases such as multiple sclerosis, endocrine system disorders, spongiform encephalopathies or chronic alcoholism.

3. Basal ganglia

The brain organization known as the basal ganglia is made up of circuits of neuronal centers connected to each otherwhich send information to each other continuously and reciprocally.

In addition, these centers located in the brain base have the capacity to link the lower regions of the brain, such as the trunk and the spinal cord, with the higher ones located in the cerebral cortex.

The different centers that make up the totality of the basal ganglia are:

• Globus pallidus.
• Nucleus accumbens.
• Caudate nucleus..
• Putamen.
• Lenticular nucleus.
• Striatum and neostriatum.
• Substantia nigra.

Although each of these centers has its own set of functions, in general, the basal ganglia play a major role in the control and execution of voluntary movements that people carry out unconsciously. That is to say, it gives us the possibility to perform all those routine activities that, although we perform them voluntarily, we do them "without thinking".

Lesions in the basal ganglia

As in the rest of the subcortical system centers, any type of lesion in the basal ganglia will have a direct effect on the functions they control. In this particular case, damage to these structures is associated with severe degenerative conditions.. These pathologies include:

• Cerebral palsy.
• Huntington's disease.
• Parkinson's disease.
• PAP syndrome.

4. Amygdala

Finally, the amygdala is a structure with an almond-shaped appearance located deep within the temporal lobes .. Like many other subcortical structures, the amygdala is formed by a series of neural centers which have their own functions.

Also known as the amygdaloid body, it is one of the structures that generates more interest in the field of psychology, since its deep brain condition makes it the main regulator of our most important emotions. the main regulator of our most basic emotionsas well as our most primal survival instincts.

Taking this information into account, we can affirm that in humans as well as in the rest of vertebrate animals, the amygdala constitutes one of the cornerstones of the evolution of the species.

The neural centers that make up the amygdala are:

• Lateral nucleus.
• Basal nucleus.
• Central nucleus.
• Median nucleus.
• Intercalated cells.

As with the basal ganglia, although each of these centers has a specific role, they are all related to feelings and emotions.

At a general level, the amygdala is responsible for emotional control, as well as for the regulation of emotions such as fear and aggressive behavioral responses. regulation of emotions such as fear and aggressive behavioral responses.. Likewise, it makes possible the recognition of emotions according to facial expressions and is responsible for emotional memory and pleasure responses.

Amygdala lesions

The abuse of toxic substances, as well as direct damage or lesions in the amygdala can cause a series of alterations related to the management of emotions.

A person with some type of impairment in the amygdaloid body may experience problems in the recognition of facial expressions that reflect emotions.. Another consequence is the lack of response to sexual stimuli or the impossibility of recognizing one's own feelings of love, happiness, anguish or anger among many others.