Supplementary Motor Area (brain): Parts And Functions
Moving is essential for our survival. However, each action we carry out is not carried out by magic: it requires a series of complex preparation and planning processes and finally the initiation of the sequence of movements required for said action.
At the brain level we find that the motor cortex is the main brain region (although not the only one) in charge of said control. And among the different areas that configure it and help the start and execution of the movement we can find the supplementary motor area one of the most important parts of the brain when it comes to interacting with the environment.
The supplementary motor area: a part of the motor cortex
The supplementary motor area It is a brain region that is part of the motor cortex this being one of the main areas of the brain that allows voluntary movements in the musculoskeletal system.
This area can be found in a strip in the upper 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 area 6.
The supplementary motor area It is, together with the premotor area, part of the secondary motor cortex which allows planning, programming and initiating control of the movements that the primary motor area will subsequently carry out.
With regard specifically to the supplementary motor area, although some of its functions and importance are not completely known, it has been seen that it has a relevant implication when it comes to initiating movement and 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. Likewise, its activity It 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
The research carried out differentiates at least two parts in the supplementary motor area.
presupplementary motor area
This part of the supplementary motor area It is characterized by activating and generating movement linked to external stimulation In other words, it is the part that generates the beginning of the movement as a reaction to the environment.
Own supplementary motor area
In this region, neuronal activity does not depend on stimulation but rather on the voluntary realization of one’s own movement It is what initiates the sequence of commands to move without needing to react to any stimulation to do so.
Features
The supplementary motor area is important in the planning and coordination of movement, as well as the motivation to start and carry it out 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 a time recovery occurs), some of those attributed to it are the following.
One of the functions most closely linked to the supplementary motor area is to generate the necessary motivation to carry out and initiate movement. This has been seen in situations in which this region was injured, akinesia appearing or lack of voluntary movement.
2. Beginning of speech
In the previous point we have mentioned that the supplementary motor area affects the initiative to move. Within the various possible movements those specific to the language are also included which is essential to allow communication to be established between the subject and other people.
3. Coordination of precise movements
Performing complex motor sequences that require great precision , such as those that require the use of both hands, depends on different brain areas. One of them is the supplementary motor area, which shows activation when faced with these types of acts.
4. Preparation for movement
The supplementary motor area is also linked to preparation for movement, activating when someone imagines performing complex movements. even if you don’t carry them out
5. Reaction to stimuli
As we have indicated, one of the parts of the supplementary motor area It is linked to the initiation and planning of movement as a reaction to environmental stimulation With this we are not referring to reflexes but to the performance of voluntary movements in specific situations.
Alterations generated by your injury
A supplementary motor area syndrome has been identified from surgical resection or injury to the area. It has been observed that resection of the supplementary motor area generates initial global akinesia and language alteration, after which incoordination, facial paralysis and hemiplegia contralateral to the lesion appear. Also motor control problems, although functionality can be recovered in a period that can last up to six months. However, sometimes some problems remain in fine movement, especially of the hands
Lesion in the left supplementary motor area usually generates transcortical motor aphasia , in which language production is not very fluid despite maintaining the ability to repeat another person’s words. Generally, there is a lack of initiative and motivation to establish communication, and dysnomia (difficulty naming) and slowing down often appear, with telegraphic language and sometimes echolalia. It is also not strange that mutism occurs 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 will to move predominates in the proximal parts of the organism. It is common for problems to appear when carrying out automated movements, although if the patient moves voluntarily there are usually no alterations.
