Cerebral cortex: its layers, areas and functions

As human beings, everything that we feel, reason and perceive, as well as our ability to move and perform any activity, has its 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 one of them has.

• Related article: "Parts of the human brain (and functions)"

What is the cerebral cortex?

The cerebral cortex refers to the outer layer of the brain. This cape consists of a thin film of nervous tissue that surrounds the surface of the cerebral hemispheres, being primates who enjoy a much more developed cerebral cortex than other animals.

Thanks to the correct functioning of the cerebral cortex, humans have the ability to perceive what happens to us and surrounds, as well as imagining, thinking, having the capacity for judgment and decision and, finally, the capacity to understand and produce the language.

Although, as explained above, the cerebral cortex is a thin layer of neurons and neuronal connections, it is not homogeneous, since it is

consists of six layers of cells, and each of them with concrete and specific functions.

• You may be interested: "Types of neurons: characteristics and functions"

Types of cerebral cortex

If we rely on both the structural and phylogenetic perspective of the cerebral cortex, we can differentiate three different classes of it. These are the following.

1. Archicortex

Evolutionarily speaking, it is the oldest part of the cerebral cortex. Formed by the hippocampus, the archicortex is in charge of those 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 kind of cortex houses the endings of the olfactory pathways, where the olfactory brain of people is found here.

3. Isocortex or neocortex

It is the area of ​​the most recent cortex, and the one in charge of the reasoning and abstract thinking processes. These regions of the central nervous system receive input from highly varied structures, and integrate this information to give way to general concepts.

• You may be interested: "The 8 higher psychological processes"

The 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 has 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 implied a powerful development of our cognitive and intellectual abilities 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 layers of the cerebral cortex.

Also known as plexiform layer, is essentially a synaptic layer formed by a thick network of neuronal fibers.

2. Outer granular layer

The second layer that makes up the cerebral cortex is the outer granular layer. This is formed by a one large number of small stellate and pyramidal cells.

The axons of this layer infiltrate the molecular layer, entering more submerged areas of the cerebral cortex, coupling with different areas of the cortex.

3. Outer pyramidal layer

The outer pyramidal layer gets its name from the type of cells that compose it: pyramidal cells. Those cells direct their axons towards other areas of the cortex and towards other subcortical destinations in the form of projection, association and commissural fibers.

4. Inner granular layer

This layer is essentially made up of a compact mass of stellate cells, most of which receive input from the thalamic area. These fibers arranged horizontally They are known as Baillarger's outer band.

5. Inner pyramidal layer, or ganglionic layer

This fifth layer contains a large number of medium and large pyramidal cells, as well as Stellate and Martinotti cells. Its horizontally arranged filaments also make up part of Baillarger's inner band.

6. Multiform or polymorphic layer

The last of these layers is formed by fusiform cells which derive information to the cortex, to the thalamus and striated nuclei. In addition, it also includes pyramidal cells with a triangular or ovoid body.

Its areas and functions

In addition to the types of bark and the layers that make it up, the cerebral cortex can be divided according to its different functional areas. That is, according to the functions or tasks carried out in each of these areas.

Taking this classification into account, the cerebral cortex can be divided into sensory, motor or association areas.

1. Sensitive areas

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

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

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

• Primary somatosensory area.
• Primary visual area.
• Primary olfactory area.
• Primary auditory area.
• Primary taste area.

2. Motor area

The areas responsible for the brain mechanisms associated with body movement are located in the anterior portion of both hemispheres, that is, in the frontal lobe. In the motor area, the descending motor treatments originate that start from the cerebral cortex towards the motor neurons of the trunk and the spinal cord.

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

• Primary motor area.
• Broca's language area.

3. Association area

Finally, the association areas are those that make possible the existence of the more complex and abstract mental functions such as memory and cognition mechanisms, the mastery of emotions, the ability to reason, and the will. In addition, they also have an influence on the development of personality and intelligence.

• Related article: "Associative cortex (brain): types, parts and functions"

Bibliographic references:

• Horton, J.C.; Adams, D.L. (2005). The cortical column: a structure without a function. Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences. 360 (1456): pp. 837 - 862.
• Moerel M, De Martino F, Formisano E (2006). An anatomical and functional topography of human auditory cortical areas. Front. Neurosci. 8(225): 225.
• Noback, C.R.; Strominger N.L.; Demarest, R.J.; Ruggiero, D.A. (2005). The Human Nervous System: Structure and Function (Sixth ed.). Totowa, NJ: Humana Press. ISBN 1-59259-730-0.
• Zuluaga, J.A. (2001). Neurodevelopment and stimulation. Madrid: Panamerican Medical.