Brain fissures: what are they, characteristics and types

Throughout evolution, the brain has become more complex by optimizing the way it organizes its structure, using a a resource as valuable as the fissures or folds, small fissures and grooves with which it extends its surface by retracting towards within.

This mechanism has allowed our species to improve certain higher cognitive functions.

In this article we explain what are brain fissures and what are its main functions and characteristics. We will also describe the most relevant fissures, including convolutions and sulci, of our brain.

• Related article: "Cerebral cortex: its layers, areas and functions"

What are fissures of the brain?

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, responsible for centralizing and processing information from our body and the environment to generate the best possible responses, depending on what each situation.

The brain can be divided into hemispheres: the right hemisphere and the left hemisphere; and in turn, in lobes: the frontal lobe, which is responsible for language and executive functions; the temporal lobe, responsible for hearing or speech; the parietal lobe, responsible for sensory-perceptual functions; the occipital lobe, whose main function is visual processing; and the

insula or insular cortex, which separates the temporal and inferior parietal lobe and plays a key role in emotional processing and subjective experience.

In neuroanatomy, when describing the different brain structures, the fissures are taken into account, which cover the surface of the cerebral cortex and give it that peculiar rough characteristic. Those "wrinkles" are essential for this organ to function properly; an absence of these can cause serious disorders, such as lissencephaly (or "smooth brain"), which can lead to motor problems, seizures and other disorders.

Fissures of the brain can be divided into convolutions and grooves that lie 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and allowing their extension to be greater; in such a way that, evolutionarily speaking, the more the brain has withdrawn inwards, the more complexity it has gained over the years, with the consequent increase and improvement of certain cognitive functions in the human species,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.

• You may be interested: "Parts of the human brain (and functions)"

Features and functions

The fissures of the brain, whether they are convolutions or grooves of greater or lesser depth, serve important functions; On the one hand, as we discussed in the introduction, these folds increase the surface area of ​​the cerebral cortex and neuronal density (without having to increase the size of the head), with the consequent improvement of higher cognitive functions in the medium and long term.

At 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 childbirth in women.

According to most scientific studies, this folding is most common in species with larger brains, such as ours, although there seem to be exceptions (such as manatees, with fewer folds than expected for a brain of their size).

However, the formation of fissures depends on other factors that go beyond growth and expansion. of the surface of the cerebral cortex, such as the physical properties of some parts of the cortex cerebral; For example, thinner regions of the brain tend to bend more easily and the brain folds into specific and consistent patterns.

Furthermore, although the brain is an interconnected organ, the various fissures are used to separate and delimit areas and structures with different functions, acting as borders that help in the division of chores.

The main grooves of the brain

There are many grooves or grooves in the brain. Next, we will talk about the best known and most relevant.

1. The interhemispheric sulcus

The sulcus or interhemispheric fissure, also known as longitudinal fissure, is a groove located in the cortex that divides the brain into two hemispheres, joined together by a set of nerve fibers called the body callous. This fissure contains a fold of the dura (the outer meninx that protects the central nervous system) and the anterior cerebral artery.

2. The lateral groove

The lateral sulcus or fissure of Silvio is one of the most visible of the brain, since it runs transversely practically the entire surface of its cortex. It is located in the lower part of the hemispheres of the brain, delimiting the border between the temporal lobe and the parietal lobe. It is also one of the deepest clefts, and below it is another relevant structure of the brain: the insula.

3. The central groove

The central sulcus or fissure of Rolando is a cleft located in the upper part of the brain and separates the lobe frontal of the temporal lobe, bordering on one side with the motor cortex and, on the other side, with the somatosensory cortex primary. This fissure would act as a bridge between motor and sensory information, integrating both.

4. The parietooccipital sulcus

The parietoocipital sulcus or external perpendicular fissure is a cleft originating from the interhemispheric fissure, being present in the inner face of each cerebral hemisphere. As its name suggests, 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 downwards and forwards. It joins the calcarine fissure below and behind the posterior end of the corpus callosum.

5. The calcarine furrow

The sulcus or calcarine fissure is a groove located in the occipital area of ​​the inner or medial face of the cerebral hemispheres, separating the visual cortex into two parts. Follows a horizontal trajectory until it joins the parieto-occipital sulcus.

6. The callous groove

The sulcus callosum is located on the medial cerebral surface and separates the corpus callosum from the cingulate, which performs relevant functions within the limbic system. Although the cingulum is usually delimited as a separate structure, it is part of the frontal and parietal lobes.

The major convolutions of the brain

As with the furrows that we have seen previously, in the brain there are also a multitude of fissures in the form of convolutions or turns, characterized by being folds with less depth than the grooves and located inside the different brain lobes. Next, we will look at some of the most important ones.

1. Gyrus 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 inferior temporal gyrus (outside) and the hippocampal gyrus (inside).

This fissure 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 lead to prosopagnosia, also called face blindness.

2. Circumvolution or cingulate gyrus

The gyrus or cingulate gyrus is an arch-shaped fissure or fold of the brain, located over the corpus callosum. Its main function is act as a link or bridge between the limbic system and the higher cognitive functions located in the neocortexTherefore, it has a fundamental role in connecting volitional, motor, memory, cognitive and affective aspects.

3. Gyrus or angular gyrus

The gyrus or angular gyrus is a fissure located in the parietal lobe, more specifically between the intraparietal sulcus and the horizontal branch of the Silvio fissure.

The functions of the angular gyrus include the processing and interpretation of language, visual and auditory information. It has connections with the Wernicke area, in charge of the auditory decoding of linguistic information.

4. Hippocampal gyrus or gyrus

This gyrus 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.

Bibliographic references:

• Allen, J. S., Bruss, J., & Damasio, H. (2005). Structure of the human brain. Research and Science, 340, 68-75.
• Clark, D.L.; Boutros, N.N. and Méndez, M.F. (2012). The brain and behavior: neuroanatomy for psychologists. 2nd edition. The Modern Manual. Mexico
• Snell, R.S. (1999). Clinical Neuroanatomy. Buenos Aires: Editorial Médica Panamericana, S.A: 267