Cerebral cortex: its layers, areas and functions

As humans, everything we feel, reason and perceive, as well as our ability to move and perform any activity, has an origin in our brain.

Throughout this article we will talk about the cerebral cortex as well as its layers and the different structures that compose it and the functions that each of them has.

    What is the cerebral cortex?

    The cerebral cortex refers to the outer layer of the brain. this layer it is made up of a thin film of nerve tissue which surrounds the surface of the cerebral hemispheres, with primates benefiting from a much more developed cerebral cortex than other animals.

    Through the proper functioning of the cerebral cortex, humans have the ability to perceive what is happening around us, as well as to imagine, think, have the ability to judge and decide, and finally the ability to understand and to produce language.

    Although, as explained above, the cerebral cortex is a thin layer of neurons and neural connections, it is not homogeneous, because it it consists of six layers of cells, And each of them with concrete and specific functions.

      Types of cerebral cortex

      If we base ourselves on both the structural and phylogenetic perspective of the cerebral cortex, three different classes of it can be differentiated. These are as follows.

      1. Arc-certainty

      Evolutionarily speaking, it is the oldest part of the cerebral cortex. Formed by the hippocampus, the archicortex is responsible for these automatic responses and physiological mechanisms responsible for survival.

      2. Paleocortex

      Phylogenetically, the paleocortex is halfway between the most primary areas of the cerebral cortex and the most evolved. This type of crust houses the endings of the olfactory pathways, where the olfactory brain of people is located.

      3. Isocoritud or neocoritud

      It is the area of ​​the most recent crust, and that in charge of abstract reasoning and thought process. These regions of the central nervous system receive afferents from a wide variety of structures, and integrate this information to make room for general concepts.

        Layers of the cerebral cortex

        As mentioned above, the cerebral cortex is made up of different layers of neural tissue known as gray matter. Each of these layers has a different functional specialization and originated at a different time in human evolution.

        This means that, throughout our evolution and development as human beings, these layers have increased in quantity, which has involved a powerful development of our cognitive and intellectual capacities compared to other animal species.

        These layers are as follows.

        1. Molecular layer

        The molecular layer is the outermost, and therefore the most recent in origin, of all the strata of the cerebral cortex.

        Also known as the plexiform layerEssentially, is a synaptic layer formed by a thick network of neural fibers.

        2. Granular outer layer

        The second layer that makes up the cerebral cortex is the outer granular layer. This consists of a 1 large number of small stellate pyramidal cells.

        Axons from this layer infiltrate the molecular layer and enter more submerged areas of the cerebral cortex, coupling with different areas of the cortex.

        3. Outer pyramid cover

        The outer pyramidal layer it takes its name from the type of cells that compose it: pyramidal cells. These cells direct their axons to other areas of the cortex and to other subcortical destinations in the form of projection, association, and commissure fibers.

        4. Internal granular coverage

        This layer is essentially made up of a compact mass of crushed cells, most of which receive afferents from the thalamic zone. These fibers are arranged horizontally they are known as the outer band of Baillarger.

        5. Inner pyramidal layer or lymph node layer

        This fifth layer involves a large number of medium and large pyramidal cells, as well as stellate cells and Martinotti. Its horizontally arranged filaments are also part of the inner Baillarger band.

        6. Multiform or polymorphic layer

        The last of these layers in that formed by spindle-like cells that derive information from the crust, thalamus and striated nuclei. In addition, it also includes pyramidal cells with a triangular or ovoid body

        Its fields and functions

        In addition to the types of crust and the layers that compose it, the cerebral cortex can be divided according to its different functional areas. In other words, according to the functions or tasks that are performed in each of these areas.

        Given this classification, the cerebral cortex can be divided into sensitive, motor or associative areas.

        1.sensitive area

        The sensitive area receives sensory information from specific nuclei of the thalamus. This information is sensitive, Which means that it carries the information perceived by the different senses: sight, hearing, smell, touch, taste …

        These same areas can also be divided into two different sensitive areas. The primary sensory zone, which has direct connections with peripheral sensory receptors; and secondary sensitive and association areas, which receive sensory information from both the primary association area and lower areas of the brain.

        The objective of the different areas of association, both primary and secondary, is to create models of recognition and behavior by assimilating sensory information. These sensitive areas of the cerebral cortex are:

        • Primary somatosensory zone.
        • Main visual area.
        • Primary olfactory zone.
        • Main hearing area.
        • Primary taste zone.

        2. Engine area

        The areas in charge of the cerebral mechanisms associated with bodily movements are located in the anterior part of the two hemispheres, that is to say in the frontal lobe. In the motor zone, the descending motor pathways originate from the cerebral cortex to the motor neurons in the trunk and the spinal cord.

        In this region we find two essential areas for our operation:

        • Main engine area.
        • Linguistic area Broca.

        3. Association zone

        Finally, the domains of association are those which allow the existence of more complex and abstract mental functions such as the mechanisms of memory and cognition, emotional control, the ability to reason and will. In addition, they also have an influence on the development of personality and intelligence.

          Bibliographical references:

          • Horton, JC; Adams, DL (2005). The cortical column: a structure without function. Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences. 360 (1456): pages 837 to 862.
          • Moerel M, De Martino F, Formisano E (2006). An anatomical and functional topography of the human auditory cortical areas. In front of. Neurosciences. 8 (225): 225.
          • Noback, CR; Strominger NL; Demarest, RJ; Ruggiero, DA (2005). The Human Nervous System: Structure and Function (Sixth Ed.). Totowa, New Jersey: Humana Press. ISBN 1-59259-730-0.
          • Zuluaga, JA (2001). Neurodevelopment and stimulation. Madrid: Médica Panamericana.

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