Somatosensory cortex: parts, functions and associated pathologies

Each region of the human brain has specific functions and burdens, which range from controlling the voluntary and involuntary movement of our muscles, to the production of language or the reception and interpretation of all sensations that arise from our environment.

This last function is possible thanks to the somatosensory cortex, A very specific area of ​​the brain that we will talk about throughout this article. In addition, we will describe their specific regions and what happens when they experience some type of injury.

    What is the somatosensory cortex?

    The concept of somatosensory cortex refers to a specific area of ​​the brain located in the parietal lobe. As the name suggests, this lobe is located under the bone of the parietal skull and in terms of size, the parietal lobe is one of the largest among those that make up the skull.

    Of all the areas that define the temporal lobe, the somatosensory cortex is the one responsible for processing and processing information of a sensory nature from the dermis, muscles and joints.

    Among the functions of the somatosensory cortex is that of receive and interpret all information coming from the touchscreen system. Sensations of pain, temperature, pressure, as well as the ability to perceive the size, texture and shape of objects are also possible through this section of the cerebral cortex.

    Likewise, the somatosensory area of ​​the brain is also responsible for receiving and transmitting information related to the position of our body in relation to the space that surrounds it.

    In summary, the main functions of the somatosensory cortex are:

    • Treatment of pain sensations.
    • Processing of tactile information.
    • Treatment of thermal sensations.
    • Treatment of vibratory sensations.
    • Voluntary hand movements.
    • Movements of the orofacial musculature.
    • voluntary swallowing.

    Finally, each of the specific areas of the somatosensory cortex is specialized in the interpretation of sensory information from certain specific areas of our body. These zones are divided between the primary somatosensory zone and the somatosensory association zone, which are described in the third and fourth points of this article.

      Layers of the somatosensory cortex

      Like the rest of the cerebral cortex, the somatosensory cortex is made up of a series of layers that have their own well-defined functions. More precisely, the somatosensory cortex is made up of six layers of nerve tissue.

      The first of these layers is the outermost, closest to the surface of the brain. One of its functions is to send sensitive signals that stimulate the fourth layer. In addition, the first and second layers of tissue receive signals that control the level of excitability of the sensory system.

      As for the second and third layers of the somatosensory cortex, its component neurons are responsible for sending signals through the corpus callosum to related regions of the corresponding cerebral cortex in the opposite hemisphere.

      Finally, the fifth and sixth layers have the main and unique function send neural signals to the deepest areas of the nervous system.

      Primary somatosensory zone

      As stated at the beginning of the article, the somatosensory cortex is divided into two specific areas. The first of these is the primary somatosensory zone. This area is the main in charge of the treatment of somatic sensations.

      The information in which these sensations are stored is sent by the receptors located along the length and width of the whole body. These receptors receive information from the outside about touch, pain and temperature, and information that allows us to know what position or situation our body is in. At the same time that these receptors perceive one of these sensations, they transmit information to the primary somatosensory cortex through the nerve fibers present in the thalamus.

      The primary somatosensory cortex refers to zones 1, 2 and 3 of the 52 brain regions described by Brodmann, which they are located specifically in the postcentral gyrus, Occupying both the lateral and medial area.

      As mentioned in the first point, each of the regions of the somatosensory cortex, in this case the primary somatosensory cortex, is specialized in receiving information from a specific area of ​​our body. This arrangement depends on the level of sensitivity of different areas of the body, therefore very sensitive areas such as the lips, hands or genitals, which have a large number of nerve endings, require many more neural circuits and one area. of the rind much more extensive.

      There is a graphic or somatotopic representation of this distribution of the primary sensory cortex. this image it is known as the sensory homunculus or Penfield. It represents a map of the cerebral cortex in which the different organs and senses of the body have a specific place in the brain.

      Outraged. in the sensory homunculus, the size of the organs represented depends on the number of nerve endings it has and the functional importance of the specific area. In other words, the more endings there are, the larger the size of the representation.

      Primary somatosensory cortex injuries

      Any type of injury or deterioration caused in this area can lead to many alterations in the ability to perceive sensations. These malfunctions include:

      • Decrease or loss of pain and thermal sensations
      • Alterations in the ability to perceive one’s own body position and movements
      • Deterioration of tactile sensations and functions

      Somatosensory association zone

      The second region of the somatosensory cortex is known as the somatosensory zone or association cortex. It happens there the union and integration of all the information corresponding to the general sensations.

      Thanks to this area of ​​the cortex, we can recognize and identify the stimuli and objects around us; because it allows the evaluation and understanding of the general characteristics of these.

      For this, this association zone, located in Brodmann zones 5 and 7, receives bundles of fibers which come from the primary somatosensory zone and which are loaded with sensory information ready to be processed.

      Association somatosensory cortex lesions

      In cases where this region suffers any kind of damage or degradation, the ability to perceive general sensations of the surroundings is maintained. However, the brain is completely unable to integrate and make sense of this information.

      This is the case with agnosias, in which the main problem is a lack of recognition of objects and people.

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