As human beings, motor control is essential in our daily lives. Often, we perform countless actions automatically, without stopping to think about which regions of our brain are being activated. One of these regions is the supplementary motor area. Are you interested in knowing what it is about? Find out in this Psychology-Online article, which will go into depth about the toSupplementary motor area: definition, location, functions and the syndrome that occurs after its injury.
What is the supplementary motor area
The supplementary motor area (SMA) is a part of the cerebral cortex, it is a premotor area whose main function is motor planning or programming and bimanual coordination.
In 1951, Penfield and Welch coined this term. However, there is still a lot to discover exactly some of its functions. In recent years, progress has been made thanks to new imaging and neurophysiology techniques, including positron emission tomography (PET) and functional magnetic resonance imaging (fMRI).
Cortical areas involved in motor control and their main functions
When we talk about motor control, the first thing that should be kept in mind is that the organization of the cortex does not only involve areas that are exclusively motor.
- First of all, there are the association areas where we find the posterior parietal cortex and the dorsolateral prefrontal cortex. These provide sensory and motivational cues for target-directed movements and select the most appropriate strategy to execute a movement.
- On the other hand, there are motor areas where the premotor areas or secondary motor cortex are located (Broadmann area 6). This is where we find the premotor cortex (lateral zone) and the supplementary motor area (superior and medial zone). These are responsible for motor planning, specifically the premotor cortex for movements triggered by external stimuli and the AMS for bimanual coordination.
- There is also the primary motor area (Broadmann area 4), which is responsible for initiating or triggering movement. Specifically, it has the function of developing the motor commands for when and how the muscles are to move.
What part of the brain controls the motor part? In the following article you will find more information about .
Location of the supplementary motor area
If you are wondering where this area is, you should know that the supplementary motor area is located on the medial aspect of the frontal lobe, in the agranular cortex of the brain. Broadmann number 6. It extends posteriorly to the primary motor cortex and inferiorly to the cingulum. That is, it is the region of the association motor cortex of the dorsal and dorsomedial areas of the frontal lobe, rostral to the primary motor cortex.
Functions of the supplementary motor area
What function does the motor area fulfill? The supplementary motor area is essential for our control of movement. His injury would produce great deficits in our daily lives. Below are some of its functions. Let’s see which ones there are:
- Motor planning or programming and bimanual coordination.
- It is involved in motor learning. Specifically in the ability to learn response sequences in which the execution of a response constitutes the signal that the next response is to be given.
- Participation in different stages of movement initiation, sequence and control of this.
- Involvement in the reception of sensory stimuli.
- Participation in working memory.
- Recovery and repetition of previously learned tasks.
- Participation in language tasks, in the control of articulation and phonation. In this article we talk about the main areas of language: .
- It acts as a connection between the limbic system and the executive motor apparatus, so that it acts by translating the motive from intention to action and exercising control over the primary motor cortex.
Supplementary motor area syndrome
What can affectation of the supplementary motor area mean? Several authors, including Pendfield, have reported cases of Transient speech motor deficits after supplementary motor area (SMA) resection. However, it has not been possible to correlate clinical findings with anatomy. One of the pioneers was Laplane (1977), who described the clinical evolution of postsurgical deficit after resections limited to the medial part of the posterosuperior region of the frontal lobe in 3 patients.
Surgery in or near the supplementary motor area can produce a set of characteristic deficit symptoms that are included in the so-called AMS syndrome. 3 stages occur:
- Immediately after surgery: global askinesia (greater on the contralateral side) and language arrest
- A few days after surgery: severe reduction in contralateral spontaneous motor activity, emotional facial paralysis and reduction in spontaneous speech.
- Time after surgery: difficulty performing alternating hand movements. This spectrum of severe but transient deficit following involvement of the ipsilateral SMA has been termed “MA syndrome.”
Some studies suggest that recovery of movement is usually complete after 11 days. Fine movements may take 2 to 6 weeks to recover. On the other hand, complex bimanual or requiring tasks may remain a permanent deficit.
Finally, add that, as has been mentioned throughout this article, this area is usually related to language and therefore it is important to mention that language deficit syndrome can appear in SMA lesions in the dominant hemisphere and is extremely characterized by mutism. However, this defect usually recovers little by little, giving way to transcortical motor dysphasia with severe predominantly motor dysphasia and telegraphic speech. There are also studies that comment on the presence of deficits such as verbal learning and alterations in the understanding and expression of language.
This article is merely informative, at Psychology-Online we do not have the power to make a diagnosis or recommend a treatment. We invite you to go to a psychologist to treat your particular case.
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Bibliography
- Carlson, N. R. (2014). Behavioral Physiology (11th Edition). Madrid: Pearson Education.
- Cervio, A., Espeche, M., Mormandi, R., Condomí Alcorta, S., & Salvat, J. (2007). Postoperative supplementary motor area syndrome: A case report. Argentine Journal of Neurosurgery, 21(3), 0-0
- Gabarrós, A., Martino, J., Juncadella, M., Plans, G., Pujol, R., Deus, J., … & Acebes, JJ (2011). Intraoperative identification of the supplementary motor area in neuro-oncological surgery. Neurosurgery, 22(2), 123-132.
- Monterroso, EM, Avilez, AB, & Vanegas, MAA (2008). Supplementary motor area. Neuroscience Archives, 13(2), 118-124.