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

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 injured.

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 the executive functions that we associate with cognitive processes such as memory use, decision making, planning and target selection or problem solving, among others.

If we divide the brain based on cytoarchitectural 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 upper 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 in the corticospinal tract (a bundle of nerve fibers running from the cortex to the spinal cord) arise from neurons in the premotor cortex. The corticospinal neurons in the premotor area control the musculature of the proximal extremities and many of their axons are connected through the inner capsule to the reticular formation of the brain stem.

The fibres that come from the premotor cortex and end in the brain stem influence the reticulo-spinal tracts , which are part of the main medial descending motor system, which is responsible for mediating body posture and locomotion, through axial and proximal control of the musculature of the extremities.

Functions

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

Research suggests that the premotor cortex is involved in the generation of time-consuming motor sequences that are retrieved from memory, and also 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, in turn, would cause bilateral activation.

Another function 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 visual stimuli. Neurons in 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 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, could also play a leading role in a human capacity as important as empathy , since it has been proven that the mirror neurons (which are activated when we do something and when we see another person doing the same) of this brain region remain active, both when we perform an action or observe it performed on others, as 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 very much associated with empathy processes.

Disorders related to the injury of this brain area

People who have lesions in the premotor cortex often show deficiencies in visually oriented movements and are unable to
correspond visual stimuli with previously learned movements.

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

On the other hand, the normal proximal-distal sequence of muscle action is also altered, and the person has pinwheel movements of the arms below shoulder level that are normal when performed forward, but abnormal when attempting to perform them backward. The cycling movements of the legs.

Another consequence associated with premotor cortex injury is the alteration of sensory orientation of movement and muscle control , which can lead to kinetic apraxia (loss of the kinetic components of gross movements) and other symptoms such as deficit 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 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, an increase in tendon reflexes and vasomotor alterations in the upper limb, contrary to the injury. 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-Vázquez, J. L., & Acuña, 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.