Subthalamus: parts, functions and associated disorders

The human brain is configured by a large number of structures and substructures that account for of the different bodily systems and of the different abilities and cognitive abilities and emotional.

All the information we collect, for example, must be integrated in order to form a concrete representation of reality. In the same way that different processes must also be integrated when responding to environmental stimulation.

There are different relay centers where these associations are made, such as the thalamus. But besides this there are different brain structures with similar functions, such as the subthalamus.

• Related article: "Parts of the human brain (and functions)"

What is the subthalamus?

The subthalamus is a complex structure linked to the management of body movement and that it has a multitude of connections with different brain regions, such as the black substance and the red nuclei, although some of their most important connections are with the pale globe.

This structure is part of the diencephalon

and is located between the brainstem and the brain hemispheres. Specifically, it can be found below the thalamus, from which it is separated by the interthalamic limiting zone, and above the midbrain (specifically the tegmentum). It also connects with hypothalamus.

In addition to those already mentioned, other structures with which the subthalamus connects include the motor cortex and prefrontal or the basal ganglia.

• Related article: "Diencephalon: structure and functions of this brain region"

Major divisions of the subthalamus

The subthalamus can be divided into the different structures that make it up. The main sections that can be considered within this brain region are the following.

1. subthalamic nucleus

One of the main structures of the subthalamus, the subthalamic nucleus, is an oval-shaped nucleus located in the central part of the uncertain zone (which we will talk about later). This brain region is of great importance due to the large number of aferences receiving. The most relevant due to its link with movement management is the relationship it has with the basal ganglia, with which it interacts through the use of glutamate.

It also has glutamatergic connections to the primary motor, prefrontal, and premotor cortex, as well as the thalamus and reticular formation.

2. uncertain zone

Located between the lenticular fasciculus and the thalamic fasciculus, the uncertain zone is one of the substructures of the subthalamus. This sheet-like nucleus is involved in the control of movement, forming part of the extrapyramidal pathway and in connection with the motor cortex. At its center is the subthalamic nucleus.

3. Forel's Cores

Nuclei of Forel's areas are three small areas of white matter of the subthalamus, also called Forel fields, which act as nerve projections to different brain regions.

Principal functions

The subthalamus is a structure of great importance for the proper functioning of the human being, having a great role in the integration of motor information that allows the management of motion. It is especially linked to involuntary aspects of movement and precise control of it, greatly affecting its connection and influence with the basal ganglia.

In addition to motor control, it has also been observed that the subthalamus influences orientation and balance, observing a greater risk of falls due to the lesion of the uncertain zone.

Lesions in the subthalamus

The presence of subthalamic lesions usually cause symptoms related to movement control. In general, a lesion in this area tends to produce sudden and involuntary movements, such as spasms and choreic movements of the extremities.

Regarding the latter, the lesion of the subthalamus is especially linked to the Huntington's chorea, in which the subthalamic nucleus is especially affected. The same is true of Sydenham's chorea.of infectious origin. The degeneration of this structure causes the choreic movements typical of these diseases.

It is also observed that the lesion of the subthalamus in its connection with the globus pallidus can generate hyperkinesia or uncontrolled excessive movements. On the other hand, it has been proposed that stimulation of this region could be useful in alleviating the symptoms of Parkinson's or other movement disorders, due to their effect on aspects such as locomotion and posture, through transcranial magnetic stimulation.

• Related article: "Parkinson's: causes, symptoms, treatment and prevention"

Bibliographic references:

• Snell, R.S. (2006). Clinical Neuroanatomy. 6th edition. Panamerican Medical Editorial. Madrid.

• Lopez, L. (2003). Functional anatomy of the nervous system. Noriega Publishers. Mexico.

• Afifi, A.K. & Bergman, R.A. (2007). Functional neuroanatomy. 2nd edition. McGraw-Hill Interamericana.