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 the management of movements and motor control of the proximal muscles and the trunk. But the functions of this motor region go further: research has suggested that it could 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 types 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 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 cytoarchitectonic 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 many axons leave the superior parietal cortex to end up in the primary motor cortex.

Nearly one-third of the axons of the corticospinal tract (a collection of nerve fibers that run from the cortex to the spinal cord) arise from neurons in the premotor cortex. Corticospinal neurons of the premotor area control the musculature of the proximal limbs, and many of their axons connect through the internal capsule to the reticular formation of the brainstem.

Fibers that come from the premotor cortex and end in the brain stem influence the reticulospinal 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 limb muscles.

Features

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, can generate a burst of nervous impulses, such that the action of the neurons can represent a repetition or the attempt to execute a certain motor response.

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

Another function related to the premotor area has to do with decision making. In research, it was found 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. The 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, apparently, also could 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 thing) in this brain region remain active, both when we perform an action or observe it performed by others, and when it is done. It is hidden and we can only infer the ending.

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 injury to this brain area

People who have lesions in the premotor cortex usually manifest impairments in visually oriented movements and are unable to match visual stimuli with previously learned movements.

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

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

Another consequence associated with injury to the premotor cortex is alteration in 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 deficits in the control of fine movements on the contralateral side and difficulties in using sensory feedback for the control and execution of tasks. motors.

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 grip reflex, spasticity, an increase in tendon reflexes and vasomotor alterations in the upper extremity, contralateral 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.