Throughout evolution, the brain has become more complex by optimizing the way it organizes its structure, using such a valuable resource as clefts or folds, small cracks and furrows with which it extends its surface by folding inward.
This mechanism has allowed our species to improve certain higher cognitive functions.
In this article we explain you what are the cerebral clefts and what are their main functions and characteristics. We will also describe the most relevant clefts, including the convolutions and furrows, in our brain.
What are brain sutures?
The human brain is an extremely complex organ made up of millions of nerve cells, as well as glial cells and blood vessels. It is a fundamental part of the central nervous system, in charge of centralizing and processing the information from our body and the environment to generate the best possible responses, depending on what each situation demands.
The brain can be divided into hemispheres: the right hemisphere and the left hemisphere; and in turn, into lobes: the frontal lobe, which is responsible for language and executive functions; the temporal lobe, which is responsible for hearing or speech; the parietal lobe, which is responsible for sensory-perceptual functions; the occipital lobe, whose main function is visual processing; and the insula or insular cortex, which separates the temporal lobe and the lower parietal lobe and plays a key role in emotional processing and subjective experience.
In neuroanatomy, when describing the different brain structures, we take into account the clefts, which cover the surface of the cortex of the brain and give it that peculiar rough characteristic . These “wrinkles” are essential for the proper functioning of this organ; an absence of them can lead to serious disorders, such as lysencephaly (or “smooth brain”), which can cause motor problems, seizures and other disorders.
The brain’s sissures can be divided into circumvolutions and grooves that are found on the entire surface of the cortex , demarcating the different cerebral lobes and hemispheres, and allowing their extension to be greater; in such a way that, evolutionarily speaking, the more the brain has retracted inwards, the greater complexity it has gained over the years, with the consequent increase and improvement of certain cognitive functions in the human species, such as language or intelligence.
Features and functions
The brain’s folds, whether they are convolutions or grooves of greater or lesser depth, fulfil important functions; on the one hand, as we commented in the introduction, these folds increase the surface of the cerebral cortex and the neuronal density (without having to increase the size of the head), with the consequent improvement of the superior cognitive functions in the medium and long term.
On an evolutionary level, this represents a great qualitative leap, since otherwise, increasing the size of the head and skull would only have been a problem for women in childbirth.
According to most scientific studies, this folding most often occurs in species with larger brains, such as ours, although there seem to be exceptions (as is the case with manatees, with fewer folds than expected for a brain of their size).
However, the formation of the clefts depends on other factors that go beyond the growth and expansion of the surface of the brain’s cortex, such as the physical properties of some parts of the brain’s cortex; for example, thinner regions of the brain tend to bend more easily and the brain folds into specific and consistent patterns .
On the other hand, although the brain is an interconnected organ, the different clefts are used to separate and delimit areas and structures with different functions, acting as boundaries that help in the division of tasks.
The main brain grooves
There are many grooves or notches in the brain. We will now talk about the most well-known and relevant ones.
1. The interhemispheric groove
The groove or interhemispheric cleft, also known as the longitudinal cleft, is an indentation located in the cortex that divides the brain into two hemispheres, linked together by a bundle of nerve fibers called the corpus callosum. This cleft contains a fold of the dura mater (the outer meninx that protects the central nervous system) and the anterior cerebral artery .
2. The side groove
Silvio’s lateral groove or fissure is one of the most visible in the brain, as it runs transversely across practically the entire surface of its cortex. It is located in the lower part of the brain’s hemispheres , delimiting the border between the temporal lobe and the parietal lobe. It is also one of the deepest clefts, and underneath it there is another relevant structure of the brain: the insula.
3. The central groove
The central groove or Rolando’s cleft is an indentation located at the top of the brain and separates the frontal lobe from the temporal lobe, bordering on one side with the motor cortex and on the other side with the primary somatosensory cortex. This fissure would bridge the gap between motor and sensory information, integrating both.
4. The parietooccipital sulcus
The parietocypital sulcus or external perpendicular fissure is a cleft that originates in the interhemispheric fissure , being present on the internal face of each cerebral hemisphere. As its name indicates, it separates the parietal lobe from the occipital lobe.
The lateral part of the sulcus is located in front of the occipital pole of the brain and the medial part goes down and forward. It joins the calcareous cleft below and behind the back end of the corpus callosum.
5. The calcareous sulcus
The calcareous groove or fissure is an indentation located in the occipital area of the inner or medial side of the brain hemispheres, separating the visual cortex into two parts. It follows a horizontal path until it joins the parietooccipital sulcus .
6. The callus groove
The callus groove is located on the medial brain surface and separates the corpus callosum from the cingulum, which performs relevant functions within the limbic system. Although the cingulum is usually defined as a separate structure, it is part of the frontal and parietal lobes.
The main convolutions of the brain
As it happens with the furrows we have seen before, in the brain there are also a multitude of curved or twisted clefts, characterized by being folds with less depth than the furrows and located inside the different brain lobes. Below, we will look at some of the most important ones.
1. Circumvolution or fusiform gyrus
The gyrus or fusiform gyrus is located on the basal surface of the cerebral hemisphere, specifically in the temporal lobe, between the lower temporal gyrus (outside) and the hippocampal gyrus (inside).
This cyst is part of the limbic system , responsible for affective processing and has an important role in facial recognition; damage to this area of the brain can cause prosopagnosia, also called face blindness.
2. Circumvolution or cingulate gyrus
The convolution or cingulate gyrus is an arched crease or fold in the brain above the corpus callosum. Its main function is to act as a link or bridge between the limbic system and the higher cognitive functions located in the neocortex , so it has a fundamental role in connecting volitional, motor, mental, cognitive and affective aspects.
3. Circumvolution or angular rotation
The convolution or angular gyrus is a fissure located in the parietal lobe, more specifically between the intraparietal sulcus and the horizontal branch of Silvio’s fissure.
The functions of angular rotation include the processing and interpretation of language, visual and auditory information . It has connections with Wernicke’s area, which is responsible for the auditory decoding of linguistic information.
4. Circumvolution or hippocampal gyrus
This convolution is located in the inner part of the temporal lobe, surrounding the hippocampus, a fundamental structure in the formation of new memories and in the spatial location.
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