Since life appeared on Earth, a great diversity of structures and beings have appeared, evolved and died. Among the different beings that have lived and live on this planet, the animal kingdom, to which we belong, is one of those that has produced the greatest visibility, interest and debate in the collective imagination.
In most of this kingdom it is possible to find one of the organs that makes our survival and the control of our body and behavior possible: the brain. In this organ, evolution has produced the appearance and development of various structures, many of them presenting a similar evolution in the majority of chordate animals.
However, in some species a structure of great relevance to explain the ability to organize, reflect or have self-awareness has largely developed, this structure being especially developed in higher primates and in us, human beings. This structure is the neocortex or neocortex
The neocortex, neocortex or isocortex It is the structure that in humans makes up most of the cerebral cortex, specifically 90% of it This is the part of the brain that has appeared most recently at a phylogenetic level. It is made up mainly of gray matter, that is, somas (the “bodies” of neurons, where the cell nucleus is located) and dendrites of the neurons that are part of the brain.
Depending on the area, this structure is between two and four millimeters thick. Despite its small thickness, it is a large structure that, due to its location within the skull, must be condensed and folded, which is why the human brain has convolutions and curvatures. In fact, although the neocortex occupies approximately the area of a pizza in its folded state, unfolded it would occupy two square meters The human brain is a unique case in the animal kingdom in terms of the ability to distribute many neuronal cell bodies in a relatively small space.
Thus, the neocortex makes it possible for there to be a multitude of neurons distributed throughout several layers of the brain folded in on themselves, and this, in turn, has great advantages for our mental performance.
On the other hand, The neocortex is not a uniform structure, but is divided into the two cerebral hemispheres Furthermore, the neocortex forms most of the different brain lobes, affecting the integration and consolidation of practically all the information that comes through the senses.
Its functions, then, are multiple and varied, as we will see below.
Principal functions
Taking into account that it makes up 90% of the cerebral cortex, it is logical to think that this part of the brain has great importance in the normal functioning of the human being. But what functions does this area have that make it so important to us?
The neocortex or neocortex is considered the brain area responsible for our reasoning ability, allowing logical thinking and awareness. This is the area of the brain that allows all higher mental functions and executive functions (especially located in the frontal lobe). It is considered that the Self and self-awareness are due to the functioning of this structure.
It is a set of neurons and glial cells whose function does not have to do with giving a stereotypical and predictable response to certain stimuli, but rather they work on contents already processed by other nerve cells to be able to “improvise” original responses in real time.
Reasoning, reflection, decision making…
Likewise the neocortex serves as an area of association and integration of different perceptions and the awareness of these, contributing to forming a more precise mental image of reality. It allows deep analysis of information, reflection and decision-making capacity.
This is the part of the brain that allows planning and anticipating results, recreating possible scenarios and allowing, based on this, the establishment of a strategy or behavior to follow.
Skills such as calculation and language also depend on the neocortex, requiring the integration of different information and its transformation in different areas of this structure. Similarly, long-term memory also depends largely on the neocortex, being the area where new information is “recorded” and from which it is taken to working memory in order to be able to operate with it.
It also allows the development and optimization of the remaining parts of the brain, being able to control behavior, manage emotions and inhibit non-adaptive behavior patterns, as well as record and consolidate new ones.
At a social level, the neocortex also has a fundamental role, since thanks to it it is possible to control and manage impulses, emotions and behaviors. This implies that it allows the existence of consideration for others, the negotiation of goals and, in general, coexistence with other members of our same species.
Organization by layers
In addition to its functional division into the different cerebral lobes and two hemispheres, it is necessary to take into account that the neocortex does not have a homogeneous composition throughout its entire length.
In fact, This part of the brain is divided into six different layers mainly due to the type and organization of the nerve cells found in them.
Layer I: Outer plexiform layer
Also called the molecular layer, it is the outermost and superficial layer of the neocortex, being covered by the pia mater (one of the meninges). This first layer contains relatively few neurons It is responsible for receiving fibers from various brain systems that send information of different types from various parts of the central nervous system.
Its composition is based mainly on horizontal cells of Cajal, dendrites of different types of neurons and interneurons and some axons of cells from other more internal layers and structures such as the thalamus. It is a layer that functions as an association layer at the intracortical level, that is, it integrates different types of information creating larger and more significant units.
Layer II: Small pyramidal cell or external granular layer
This layer of the neocortex is composed mainly of pyramidal and stellate cells (star-shaped), whose dendrites are located in the external plexiform layer and the axons in lower layers. Like the previous one, it serves as an association mechanism between the different parts of the cortex, although at another level.
Layer III: External pyramidal layer
Composed mainly of pyramidal cells of variable size, although generally higher than that of the external granular layer. Their axons configure projection and association fibers. It serves as an intracortical association area. Likewise, some of its neurons project contralaterally (to the other cerebral hemisphere), so that a bridge is established between these two halves of the upper part of the central nervous system.
Layer IV: Inner granular layer
This layer is mainly composed of star-shaped cells. This layer does not exist in some areas, such as in the motor cortex. It receives information from the thalamus, which is distributed by this layer in what is known as thalamocortical striae. Its fibers project to the basal ganglia, spinal cord, and brainstem.
Layer V: Internal pyramidal or ganglionic layer
The fifth layer of the neocortex is made up of large pyramidal cells, along with other stellates, which send information to other areas of the brain. Within this layer you can see Baillarger’s band, a group of nerve fibers located horizontally and that can be distinguished from the adjacent areas that make up the neocortex.
Layer VI: Polyform layer
Made up of cells of irregular and polymorphic shapes, This layer of the neocortex performs efferent functions, sending connections to the white matter and traveling many of its neurons through the corpus callosum. That is, it sends information to relatively distant areas, more than it receives directly from them.
