Premotor cortex: characteristics and functions of this brain area

The premotor cortex is located in the frontal lobe of the human brain., a brain region that is mainly responsible for managing movements and motor control of proximal muscles and the trunk. But the functions of this motor region go further: the investigations carried out have suggested that could be involved in high-level cognitive processes, such as empathy or decision-making decisions.

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

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Premotor cortex: definition, location and characteristics

The premotor cortex is one of the structures that make up the motor areas of the brain, and is located in the frontal lobe, a region related to 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 based on cytoarchitectural criteria, the premotor cortex It 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 large numbers of axons leave the superior parietal cortex to terminate in the primary motor cortex.

Nearly one third of the axons of the corticospinal tract (a bundle of nerve fibers running from the cortex to the spinal cord) arise from neurons in the premotor cortex. Corticospinal neurons in the premotor area control the musculature of the proximal extremities and many of its axons connect through the internal capsule to the reticular formation of the stalk cerebral.

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

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functions

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

Research suggests that the premotor cortex is involved in generating motor sequences that are retrieved from memory and that require precise timing, as well as plays an important role in conditioned motor learning. In addition, in some studies it has been observed that the passive vision of faces activates the right ventral premotor area, and imitative vision, for its part, would cause bilateral activation.

Another of the functions related to the premotor area has to do with decision making. In an investigation it was possible to verify that this is a fundamental structure in this cognitive process, since it would play a key role in the different phases of decision-making based on stimuli visuals. 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 closely related to the selection of a specific movement or a sequence of movements or repertoire of possible movements. The functions of both areas differ, however, in the relative contributions of external and internal signals to the selection process. movements: the medial portion would be specialized in movements generated by internal signals and the lateral portion in the external.

The premotor cortex, it seems, also could play a leading role in a human capacity as important as empathy, since it has been proven that mirror neurons (which are activated when we do something and when we see another person do the same) in this region brain remain active, both when we perform an action or observe it performed in others, 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 processes of empathy.

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Disorders related to damage to this brain area

People with lesions in the premotor cortex often manifest impairments in movements that are visually oriented and they are unable to do that. Match visual stimuli with previously learned movements.

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

On the other hand, the alteration of the normal proximal-distal sequence of muscular action also occurs, and the person presents movements of twirl of the arms below shoulder level normal when performed forward, but abnormal when attempting to perform forward back. The bicycle movements of the legs.

Another of the consequences associated with damage to the premotor cortex is impaired sensory orientation of movement and muscle control, which can cause kinetic apraxia (loss of the kinetic components of gross movements) and other symptoms such as deficit in control of fine movements of the contralateral side and difficulties in using sensory feedback for control and execution of tasks motor.

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

Bibliographic references:

• Freund, H. J., & Hummelsheim, H. (1985). Lesions of premotor cortex in man. Brain, 108(3), 697-733.
• Pardo-Vazquez, J. L., & Acuna, C. (2014). Neural bases of perceptual decisions: role of the 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.