Premotor cortex: characteristics and functions of this brain area

The premotor cortex is not only involved in processes related to movement.

The premotor cortex is located in the frontal lobe of the human brain.This brain region is mainly responsible for movement management and motor control of the proximal muscles and the trunk. But the functions of this motor region go beyond that: research has suggested that it may be involved in higher-level cognitive processes, such as empathy or decision-making.

Throughout the article we explain what the premotor cortex is, what its main characteristics and functions in the brain are, and what kind of disorders can occur if this area is damaged.

Premotor cortex: definition, location and characteristics.

The premotor cortex is one of the structures that make up the motor areas of the brain, and it is located in the frontal lobe.It is located in the frontal lobe, a region related to the executive functions that we associate with cognitive processes such as the use of memory, decision making, planning and selection of objectives or problem solving, among others.

If we divide the brain on the basis of cytoarchitectonic criteria, the premotor cortex is located in Brodmann area 6, just before the primary motor cortex.. The premotor cortex receives most of its information from the superior parietal cortex, and a large number of axons leave this cortex to end up in the primary motor cortex.

Nearly one third of the axons of the corticospinal tract (a bundle of nerve fibers leading from the cortex to the spinal cord) arise from neurons in the premotor cortex. Corticospinal neurons of the premotor area control the proximal limb musculature and many of their axons connect through the internal capsule to the reticular formation of the brain stem.

Fibers originating in the premotor cortex and terminating in the brain stem influence the reticulospinal tracts, which are part of the descending motor system.These are part of the main medial descending motor system, which is responsible for mediating body posture and locomotion through axial and proximal control of limb musculature.

Functions

The premotor cortex is activated when motor action programs are initiated or when previously learned programs are modified. Neurons in the premotor area transmit impulses in anticipation of movements.. A learned cue, for example, may generate a burst of nerve impulses, such that the action of neurons may represent a repetition or attempt to execute a particular motor response.

Research suggests that the premotor cortex is involved in the generation of motor sequences that are retrieved from memory and require precise timing, and also plays an important role in motor learning. plays an important role in conditioned motor learning.. Furthermore, in some studies it has been observed that passive vision of faces activates the right ventral premotor area, and imitative vision, on the other hand, would provoke a bilateral activation.

Another function related to the premotor area has to do with decision making. Research has shown that this is a fundamental structure in this cognitive process, as it plays a key role in the different phases of decision making based on visual stimuli. The neurons of the premotor area encode and compare the information received so that the organism can adjust and adapt its behavior to what each specific situation requires.

Most studies have suggested that the lateral and medial areas of the premotor cortex are intimately involved with the selection of a specific movement or a sequence of movements or repertoire of possible movements.. The functions of the two areas differ, however, in the relative contributions of external and internal signals to the movement selection process: the medial portion would be specialized in movements generated by internal signals and the lateral portion in external ones.

The premotor cortex, it seems, may also play a role in such important may also play a leading role in such an important human ability as empathyIt has been shown that the mirror neurons (which are activated when we do something and when we see another person do the same thing) in this brain region remain active, both when we perform an action or observe others performing it, and when it is hidden and we can only infer the end.

The latter means that we generate internal motor representations of the actions that other people carry out in the premotor cortex, which makes it easier for us to understand their personal dispositions and intentions, something closely associated with empathy processes.

Disorders related to the lesion of this brain area.

People who present lesions in the premotor cortex usually manifest deficiencies in movements that are visually oriented and are unable to match visual stimuli correspond visual stimuli with previously learned movements.

Unilateral lesions in the premotor area result in moderate weakness of the shoulder and contralateral pelvic muscles. moderate weakness in the shoulder muscles and contralateral pelvic muscles.. In addition, although forearm strength is not affected, gripping movements are impaired when they depend on the supporting action of the shoulder, movements are slow and there is a disturbance in their kinetic structure.

On the other hand, there is also disturbance of the normal proximal-distal sequence of Muscle action, and the person exhibits normal below shoulder level arm windlass movements when performed forward, but abnormal when attempting to perform them backward. Bicycling movements of the legs.

Another of the consequences associated with premotor cortex lesioning is alteration in the sensory orientation of movement and muscle control, which can lead to kinetic apraxia (loss of the kinetic components of gross movements) and other symptomsThis can lead to kinesthetic apraxia (loss of the kinetic components of gross movements) and other symptoms such as deficits in the control of fine movements on the contralateral side and difficulties in using sensory feedback for the control and execution of motor tasks.

Another disorder resulting from damage to the premotor area that has been studied, both clinically and experimentally, is the so-called premotor cortex syndrome. the so-called premotor cortex syndromecharacterized by the presence of the grasp reflex, spasticity, increased tendon reflexes and vasomotor disturbances in the upper limb contralateral to the lesion. This varied symptomatology has also been defined as an intellectual deficit, because patients seem to forget how to perform certain learned movements.

Bibliographical references:

• Freund, H. J., & Hummelsheim, H. (1985). Lesions of premotor cortex in man. Brain, 108(3), 697 - 733.
• Pardo-Vázquez, J. L., & Acuña, C. (2014). Neural basis of perceptual decisions: role of ventral premotor cortex. Journal of Neurology, 58(9), 401 - 410.
• Rizzolatti, G., Fadiga, L., Gallese, V., & Fogassi, L. (1996). Premotor cortex and the recognition of motor actions. Cognitive brain research, 3(2), 131 - 141.