Supplementary motor area: what it is, function and injury

  • Jul 26, 2021
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Supplementary motor area: what it is, function and injury

As human beings, motor control is essential in our day to day. Often times, we perform endless actions automatically, without stopping to think 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 delve into the áSupplementary motor area: definition, location, functions and the syndrome that occurs after injury.

You may also like: Broca and Wernicke's area: differences and functions

Index

  1. What is the supplementary motor area
  2. Location of the supplementary motor area
  3. Functions of the supplementary motor area
  4. Supplemental motor area syndrome

What is the supplementary motor area.

The supplemental motor area (AMS) is a part of the cerebral cortex, it is a premotor area whose main function is the motor planning or programming and bimanual coordination.

In 1951, Penfield and Welch coined this term. However, there is still much 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 borne in mind is that the organization of the cortex does not only involve areas that are exclusively motor.

  • First, there are association areas where we find the posterior parietal cortex and the dorsolateral prefrontal cortex. These provide sensory and motivational clues to movements directed at a target and select the most appropriate strategy to execute a movement.
  • On the other hand, there are motor areas where are the premotor areas or secondary motor cortex (Broadmann area 6). This is where we find the premotor cortex (lateral zone) and the supplementary motor area (upper and medial area). These are responsible for motor planning, specifically the premotor cortex of movements triggered by external stimuli and the AMS of bimanual coordination.
  • There is also the primary motor area (Broadmann area 4), which is responsible for initiating or triggering the movement. Specifically, it has the function of elaborating the motor orders of when and how the muscles have to move.

What part of the brain controls the motor part? In the following article you will find more information about The cerebral cortex: functions and parts.

Location of the supplementary motor area.

If you wonder where this area is, you should know that the supplementary motor area is located in the medial aspect of frontal lobe, in the agranular cortex of Broadmann number 6. It extends posteriorly to the primary motor cortex and inferiorly to the cingulate. That is, it is the region of the motor cortex of association of the dorsal and dorsomedial zones of the frontal lobe, rostral to the primary motor cortex.

Supplementary motor area: what it is, function and injury - Location of the supplementary motor area

Functions of the supplementary motor area.

What is the function of the motor area? The supplementary motor area is essential for our control of movement. His injury would produce large deficits in our day to day. Here are some of its functions. Let's see which ones there are:

  1. Planning o motor programming and bimanual coordination.
  2. It is involved in the motor learning. Specifically in the ability to learn response sequences in which the execution of a response constitutes the signal that the next response must be given.
  3. Participation in different stages of the initiation of movement, sequence and control of this.
  4. Involvement in reception of sensitive stimuli.
  5. Participation in the work memory.
  6. Recovery and repetition of previously learned tasks.
  7. Participation in language tasks, in the control of articulation and phonation. In this article we talk about the main areas of language: Broca and Wernicke area.
  8. It acts as a connection between the limbic system and executive motor apparatusThus, it acts by translating the motive from intention to action and exerting control over the primary motor cortex.

Supplemental motor area syndrome.

What can the affectation of the supplementary motor area mean? Several authors, including Pendfield, have reported cases of transient motor speech deficits after supplemental motor area (AMS) resection. However, the clinical findings could not be correlated with the anatomy. One of the pioneers was Laplane (1977), who described the clinical evolution of the postsurgical deficit after resections circumscribed to the medial part of the posterior superior region of the frontal lobe in 3 patients.

Surgery in the supplementary motor area or in the vicinity of it, can produce a set of characteristic deficit symptoms that are included in the so-called AMS syndrome. 3 stages occur:

  1. Immediately after surgery: global askinesia (greater on the contralateral side) and language arrest
  2. A few days after surgery: severe reduction of contralateral spontaneous motor activity, emotional-type facial paralysis and reduction of spontaneous speech.
  3. Time after surgery: Difficulty performing alternating movements with the hands. This spectrum of severe but transitory deficit after ipsilateral AMS involvement has been termed "AM syndrome."

Some studies suggest that recovery from movement is usually complete at 11 days. Fine movements can take 2 to 6 weeks to recover. Instead, complex bimanual or requiring tasks may remain a permanent deficit.

Finally, add that, as mentioned throughout this article, this area is usually related to language and therefore is It is important to mention that the deficit language syndrome can appear in lesions of the SMA in the dominant hemisphere and is characterized in a extreme by mutism. However, this defect usually recovers little by little, giving way to a transcortical motor dysphasia with severe dysphasia predominantly motor 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, in 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.

If you want to read more articles similar to Supplementary motor area: what it is, function and injury, we recommend that you enter our category of Neuropsychology.

Bibliography

  • Carlson, N.R. (2014). Physiology of Behavior (11 Edition). Madrid: Pearson Education.
  • Cervio, A., Espeche, M., Mormandi, R., Condomí Alcorta, S., & Salvat, J. (2007). Postoperative supplementary motor area syndrome: Report of a case. Argentine journal of neurosurgery, 21(3), 0-0
  • Gabarrós, A., Martino, J., Juncadella, M., Plans, G., Pujol, R., Deus, J.,... & Acebes, J. J. (2011). Intraoperative identification of the supplementary motor area in neurooncological surgery. Neurosurgery, 22(2), 123-132.
  • Monterroso, E. M., Avilez, A. B., & Vanegas, M. TO. TO. (2008). Supplementary motor area. Neuroscience Archives, 13(2), 118-124.
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