In the frontal lobe of the human brain is the premotor cortex, A region of the brain that is primarily responsible for movement management and motor control of the proximal muscles and trunk. But the functions of this motor region go further: 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 features and functions it performs in the brain, and what types 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 is located in the frontal lobe, a region related to executive functions that we associate with cognitive processes such as memory usage, decision making, planning and goal selection, or problem solving , among others.
If we divide the brain according to cytoarchitectonic criteria, the premotor cortex is located in Brodmann zone 6, just before the primary motor cortex. The premotor cortex receives most of the information from the superior parietal cortex, and a large number of axons leave this cortex and end up in the primary motor cortex.
Almost a third of the axons in the corticospinal tract (a collection of nerve fibers that run from the cortex to the spinal cord) originate from neurons in the premotor cortex. Corticospinal neurons in the premotor zone control the muscles of the proximal limbs and many of their axons connect through the internal capsule to the reticular formation of the brainstem.
Fibers that originate from the premotor cortex and end in the brain stem influence the reticospinal pathways, Which are part of the main median descending motor system, which is responsible for intervening in body posture and locomotion, by axial and proximal control of the muscles of the limbs.
The premotor cortex is activated when motor action programs are initiated or when previously learned programs are changed. Neurons of the premotor zone they transmit impulses in anticipation of movements. A learned key, for example, can generate a burst of nerve impulses, so the action of neurons can represent a repetition or attempt to execute a given motor response.
Research suggests that the premotor cortex is involved in the generation of motor sequences that are retrieved from memory and require specific time, as well as plays an important role in conditioned motor learning. In addition, in some studies it has been observed that passive vision of the face activates the right ventral premotor zone and imitative vision, in turn, would cause bilateral activation.
Another of the functions related to the premotor zone concerns decision making. Research has shown that it is a fundamental structure in this cognitive process, as it is thought to play a key role in the different phases of decision-making based on visual stimuli. Neurons in the premotor zone encode and compare the information received so that the body can adjust and adapt its behavior to what each specific situation requires.
Most studies suggest 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 a repertoire of possible movements. The functions of the two zones differ, however, in the relative contributions of external and internal signals to the movement selection process: the middle part would be specialized in movements generated by internal signals and the lateral part towards external signals.
The premotor cortex, it seems, too he could play a leading role in a human capacity as important as empathySince it has been shown that the mirror neurons (which are activated when we do something and when we see another person doing the same) in this brain region remain active, either when we perform an action or when we do it. let us observe perform in others, as this is hidden and we can only infer at the end.
The latter means that we generate internal motor representations of the actions that other people perform in the premotor cortex, making it easier for us to understand their personal dispositions and intentions, which is very associated with empathy processes.
Disorders related to the lesion of this brain area
People who have lesions in the premotor cortex usually show up impairments in visually oriented movements and are unable to match visual stimuli with previously learned movements.
Unilateral lesions in the premotor zone generate moderate weakness of shoulder muscles and contralateral pelvic muscles. In addition, although the resistance of the forearm is not affected, the holding movements deteriorate when dependent on the supporting action of the shoulder, the movements are slow and a disruption of its structure. kinetics occurs.
On the other hand, there is also the alteration of the normal proximal-distal sequence of muscular action, and the person has normal arm movements of the arms below the level of the shoulder when executed towards the shoulder. ‘before, but abnormal when trying to run them. backward. Cycling movements of the legs.
Another consequence associated with injury to the premotor cortex is impaired sensory orientation, movement and muscle control, Which can cause kinetic apraxia (loss of the kinetic components of heavy movements) and other symptoms such as a deficit in the control of fine movements of the contralateral band and difficulty using sensory feedback to control and perform motor tasks.
Another of the disorders derived from damage to the premotor zone that has been studied, both clinically and experimentally, is the so-called premotor cortex syndrome, Which is characterized by the presence of the gripping reflex, spasticity, an increase in tendon reflexes and vasomotor alterations of the upper limb, contralateral to the injury. This varied symptomatology has also been defined as intellectual deficit, as patients seem to forget how to perform certain learned movements.
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- Pardo-Vázquez, JL and Acuña, C. (2014). Neural basis of perceptual decisions: role of the ventral premotor cortex. Journal of Neurology, 58 (9), 401-410.
- Rizzolatti, G., Fadiga, L., Gallese, V. and Fogassi, L. (1996). Premotor cortex and recognition of motor actions. Cognitive brain research, 3 (2), 131-141.