Supplementary motor area (cerebrum): parts and functions

This part of the brain allows us to relate to the environment and to others.

Moving is fundamental to our survival. However, every action we perform does not happen by magic: it requires a series of complex processes of preparation and planning and finally the initiation of the sequence of movements required for that action.

At the level of the brain, we find that the motor cortex is the main brain region (although not the only one) in charge of this control. And among the different areas that configure it and help the initiation and realization of the movement we can find the supplementary motor areaone of the most important parts of the brain when interacting with the environment.

The supplementary motor area: a part of the motor cortex.

The supplementary motor area is a brain region that is part of the motor cortex, which is one of the main areas of the brainThis is one of the main areas of the brain that allows the realization of voluntary movements in the musculoskeletal system.

This area can be found in a strip in the superior and medial part of both hemispheres, in the frontal lobe. Specifically, it is located in front of the primary motor cortex, which in turn is located immediately anterior to Rolando's fissure. It corresponds to Brodman's area 6.

The supplementary motor area is, together with the premotor area, part of the secondary motor cortex, which allows planning, programming and initiation of the motor function.which allows planning, programming and initiating the control of the movements that the primary motor area will subsequently carry out.

Regarding specifically the supplementary motor area, although part of its functions and importance are not completely known, it has been found to have a relevant implication in initiating movement and in the motivation and activation necessary to produce a movement.

Its connection with the limbic system and the basal ganglia generates a relationship between movement and motivation. is important not only in the initiation of the movement but also in its preparation and monitoring.. For example, a relationship has been seen between this area and motor coordination in those situations that require precise and complex control.

Divisions of this part of the brain

Research differentiates at least two parts of the supplementary motor area.

Presupplementary motor area

This part of the supplementary motor area is characterized by activation and movement linked to external stimulation.. In other words, it is the part that generates the initiation of movement as a reaction to the environment.

Supplementary motor area proper

In this region the neuronal activity does not depend on stimulation but rather on the voluntary realization of the movement itself. It is the one that initiates the sequence of commands to move without the need to react to any stimulation to do so.

Functions

The supplementary motor area is important in the planning and coordination of movement, as well as in the motivation to initiate and carry out the movement.. Although its real importance and some of its functions are not completely known (for example its resection alters different functions but nevertheless in many cases after some time there is a recovery), some of those attributed to it are the following.

1. Motivation and movement initiation

One of the functions most closely linked to the supplementary motor area is that of generating the motivation necessary to perform and initiate movement. This has been seen in situations in which this region was injured, resulting in akinesia or lack of voluntary movement. or lack of voluntary movement.

2. Speech initiation

In the previous point we mentioned that the supplementary motor area affects the initiative to move. Among the various possible movements also include the movements of languageThis is essential to establish communication between the subject and other people.

3. Coordination of precise movements

The realization of complex motor sequences that require great precision, such as those that require the use of both hands.such as those requiring the use of both hands, depends on different brain areas. One of them is the supplementary motor area, which shows activation before this type of acts.

4. Preparation for movement

The supplementary motor area is also linked to the preparation for movement, being activated when someone imagines performing complex movements even if he/she does not perform them..

5. Reaction to stimuli

As we have indicated, one of the parts of the supplementary motor area is linked to the initiation and planning of movement as a reaction to environmental stimulation.. By this we are not referring to reflexes but to the realization of voluntary movements in specific situations.

Alterations generated by the lesion

A supplementary motor area syndrome has been identified following surgical resection or lesion of the area. It has been observed that resection of the supplementary motor area generates initial global akinesia and language impairment, after which incoordination, facial paralysis and hemiplegia contralateral to the lesion appear. Also motor control problems, although functionality can be recovered in a period of up to six months. However, some fine movement problems some fine movement problems remain, especially of the hands..

The lesion in the left supplementary motor area usually generates transcortical motor aphasia, in which language production is impaired.The lesion in the left supplementary motor area usually results in transcortical motor aphasia, in which language production is not very fluent despite maintaining the ability to repeat the words of another person. Generally, there is an absence of initiative and motivation to establish communication, with frequent dysnomia (difficulty in naming) and slowing, with telegraphic language and sometimes echolalia. It is also not uncommon for mutism to be present and the subject does not speak or communicate.

Also at the level of movement, these are reduced to a minimum in what is known as akinesia, although the loss of willingness to move in the proximal parts of the body predominates. It is common for problems to appear in the realization of automated movements, although if the patient moves voluntarily there are usually no alterations.

Bibliographic references:

• Cervio, A.; Espeche, M.; Mormandi,R.; Alcorta, S.C. & Salvat, S. (2007). Postoperative supplementary motor area syndrome. Report of a case. Argentine journal of neurosurgery, 21 (3). Autonomous City of Buenos Aires.
• Herrera, R.F. (2012). Clinical syndrome due to supplementary motor area removal in patients with brain gliomas. Doctoral dissertation. Inter-American Open University. Rosario Regional Office. School of Medicine and Health Sciences.
• Monterroso, M.E.; Avilez, A.B. y Vanegas, M.A.A. (2008). Supplementary motor area. Arch. Neurocien, 13 (2): 118-124. Mexico.