The postcentral gyrus is an area of the cerebrum. It is located in the parietal lobe and plays a role in somatosensory processing. Damage to the postcentral gyrus results in astereognosia, which is reflected as disturbances in touch sensitivity, pain and temperature perception, and vibration sensation and proprioception.
What is the postcentral gyrus?
The postcentral gyrus is a part of the cerebrum that belongs to the parietal lobe. The parietal lobe is located centrally in the brain behind the frontal lobe; medicine also refers to the parietal lobe as the parietal lobe because of its location. Like the other gyri of the brain, the postcentral gyrus is a brain turn that appears as an elongated bulge. The counterpart to the gyri are the sulci. A sulcus is a furrow in the brain structure. Sulci and gyri do not only form optically delimitable units: They also perform specific functions, since the nerve and glial cells within such a unit have many connections among themselves. The numerous synapses enable the cells within a gyrus to work together synergistically and effectively. The postcentral gyrus is located behind the sulcus centralis – the central groove of the cerebrum.
Anatomy and structure
The postcentral gyrus plays an important role in sensory perception: it contains the somatosensory cortex. This is the processing center for haptic stimuli such as touch. The somatosensory cortex extends not only over the postcentral gyrus, but also over adjacent brain structures. The postcentral gyrus contains the largest part of the somatosensory cortex, which includes Brodmann areas 1, 2, 3a, and 3b. Medicine delineates these areas from each other based on their different structures. The psychiatrist Korbinian Brodmann introduced this classification in 1909. Areas 1, 2 and 3 represent the primary sensitive areas of the haptic information processing center. The secondary-sensitive areas, which complement the primary-sensitive ones, are located in Brodmann areas 40 and 43. Because of their function, medicine also refers to the secondary-sensitive areas as association areas.
Function and tasks
The postcentral gyrus can be further subdivided into units that are distinguished on the basis of their function. Individual clusters of neurons each represent a body region and map it in the brain. Within this representation, the brain primarily processes haptic information from the corresponding body region. Such a mapping or representation of body regions in the brain is called somatotopy in medicine. However, somatotopy does not have the same proportions as life-size body regions. A body part reacts somatosensory the more sensitive, the more neurons represent it in the brain. The representation accordingly occupies a larger or smaller area in the postcentral gyrus. The midline neurons of the postcentral gyrus to the mantle edge are responsible for the lower extremities. Adjacent to this are the processing areas for the trunk and upper extremities. The representation of the hands takes up a particularly large amount of space, since they are very sensitive to tactile stimuli in humans. Laterally, the representation of the tongue and head follows. Medicine also summarizes this area as the parietal operculum. The operculum is the motor speech center. The somatosensory cortex is constantly active in the background. When a person reaches for a glass of water, the body must calculate exactly how much pressure the hand may exert against the glass, how much the muscles must contract, and how the grip must strengthen as the person lifts, moves, or raises the glass to the mouth. One of the prerequisites for this simple process is therefore haptic perception. In this context, neurology distinguishes between the senses of force and resistance, position perception and the sense of movement.
Diseases
Damage or lesion in the postcentral gyrus can lead to deficits in certain areas of perception. This is the case, for example, when individual processing areas no longer function correctly, the communication of neurons within the postcentral gyrus is disrupted, or the exchange of information with other brain areas fails. The result is astereognosia or tactile agnosia.Medical professionals use this term to describe the inability to palpate shapes and correctly recognize somatosensory stimuli. They lead to a variety of different complaints, which the perceptual disorder causes. However, the individual symptoms may differ from one another in individual cases and may vary in severity. Affected persons are more sensitive to touch and suffer from a disturbance in pain perception (nociception). Impaired pain perception can manifest itself at all levels: Both the perception of pain on the surface of the body and deep pain in the muscles and bones may be affected. Disorders may also occur with respect to visceral pain perception. Visceral pain involves perceptions from the organs. Furthermore, people with damage to the postcentral gyrus may not be able to sense temperature because the somatosensory cortex does not properly process information from the heat and cold receptors. In addition, when doctors examine depth sensitivity (proprioception), they may notice deterioration in this area of function – both in the sense of force and resistance and in the sense of position or movement. Affected individuals may also suffer from a disturbance in vibration sensation or pallesthesia. Impairment of the postcentral gyrus may have various causes. Typical are direct damage due to injuries, for example after an accident, and space-occupying tumors. In addition, the postcentral gyrus may be associated with parasomnia. This sleep disorder is manifested by conspicuous sleep behavior and is probably due to increased activity in the postcentral gyrus during deep sleep.
