The human brain is a very complicated and fascinating organ. It is one of the most important organs, being responsible for controlling every living action our bodies make, be they conscious or unconscious. The central sulcus is an interesting and important part of the brain.
The central sulcus is the central groove found in the cerebral cortex of the brain, it is also known as the Rolando Fissure. The central sulcus connects the frontal and parietal lobes. The central sulcus further functions in separating the primary somatosensory cortex from the primary motor cortex.
While the above may sound overwhelming, this article will help you to understand how the central sulcus develops, where exactly it is located, and of course, what its function is. We will also have a look at how deformations in the central sulcus can play a role in how we function as well as our abilities.
What Is The Central Sulcus?
The central sulcus is one of a number of sulci that make up the cerebral cortex of the brain and is so named as it occurs in the center of the lateral surface of the brain and separates the frontal and parietal lobes of the brain.
The central sulcus is also known as the Rolando fissure, being named after an Italian anatomist Luigi Rolando, who, during the 18th century, was a pioneer in understanding the areas of the brain and their differing functions.
What Is A Sulcus
To begin, let us first understand what a sulcus is. Sulci are the grooves that are found on the cerebral cortex, which is the outer covering of the brain. Sulci, along with the gyri, help to increase the surface area of the brain. Gyri form the crests of the cerebral cortex, while the sulci are the troughs or furrows that together create the wavy wrinkled appearance of the brain.
Together with the gyri, the sulci help to partition the brain into segments. These segments are known as lobes. The brain has four lobes which are determined by the positioning of the sulci. The frontal lobe, the parietal lobe, the temporal lobe and the occipital lobe.
Some sulci develop before birth and are considered primary sulci, sulci that develop during the course of one's life are considered to be secondary sulci. Very deep sulci are also known as fissures, the largest and deepest sulcus is the longitudinal fissure that separates the brain into left and right hemispheres, whereas the central sulcus is also known as the Rolando fissure.
Sulci can also be termed complete or incomplete based on their depth. Complete sulci are deep, while incomplete sulci are shallower in depth.
Why Is The Cerebral Cortex’s Large Surface Area Important
Increasing the surface area of the cerebral cortex is an important role of the sulci and gyri. The cerebral cortex is a thin covering of just a few millimeters in thickness, but due to the folds and wrinkles created by the sulci and gyri, this brain covering can make up almost 50% of the brain matter.
That the cerebral cortex is made up of so much brain tissue is integral to the functioning of the brain. The cerebral cortex is composed mainly of grey matter which is made up of billions of nerve cells called neurons. These neurons are responsible for the efficient working of the brain and are how we store data.
The cerebral cortex containing this grey matter is, therefore, the data center of the brain. The larger the surface area, the more data the brain will be able to store and work with.
Where Is The Central Sulcus Located
The central sulcus forms part of the cerebral cortex, runs centrally across the lateral surface of the brain and is positioned at what could be considered perpendicularly across the longitudinal fissure at its midpoint. As it is a sulcus, it is not a straight line due to the wrinkled and grooved nature of sulci and gyri.
The central sulcus is the boundary between the primary motor cortex and the primary somatosensory cortex. It also serves to divide the parietal and frontal lobes.
The shape of the central sulcus is not exact, and it will change over time as the sulcus develops. Nonetheless, the central sulcus does have a generally understood morphology, and abnormalities can indicate complications.
Development Of The Central Sulcus
As mentioned earlier, the central sulcus begins development while a fetus is still in the womb. This development starts at about 13 weeks of gestation. During the initial 2 weeks of growth, the central sulcus will develop quickly, so from 13 to 15 weeks of gestation. Thereafter it will slow down for a few weeks.
The greatest growth spurt is experienced between 18 and 19 weeks of gestation. It is characterized by the migration of neurons and fibers which start their movement from the parasagittal region of the brain.
By the time the fetus reaches 22 to 23 weeks of gestation, the central sulcus becomes more apparent and extends towards both the longitudinal and the lateral fissures.
The center will continue to develop throughout a person's life. However, there are two major markers during its development.
The first occurs in early childhood, where at some point between the ages of two and three, the Pli de Passage Frontoparietal Moyen (PPFM), a deeper hollow located at the center of the central sulcus, will become apparent.
The second is that from the age of three, the central sulcus will have developed a depth and curve which is much like that of an adult. By the age of 3, major changes and development are complete. However, as noted earlier, the central sulcus will continue to develop throughout the lifetime of a human.
The development of the central sulcus is due to the development of motor functions which explains why the greatest changes and development occur at a young age, where young humans develop the fastest.
A number of other factors influence the development of the shape central sulcus.
Factors Influencing the Development Of The Central Sulcus
Both genetic and non-genetic elements can determine the shape and development of the central sulcus. Genetic factors will more fully influence the structural depth of the central sulcus, while non-genetic factors will more likely influence the superficial shaping of the central sulcus.
The following are the elements that play a role in the development of the central sulcus.
- Biological gender
- Age
- Surface area
- Motor function
Biological Gender
The biological gender of a person can play a role in the size and width of the central sulcus. Biologically male individuals exhibit a central sulcus with a larger width than their biologically female counterparts. What is of interest is that this additional width is limited to the central sulcus on the right hemisphere of the brain.
The central sulcus of the biologically female sex will generally be wider on the left hemisphere.
That being said over time the overall width of the central sulcus does increase more in males than in females with age.
Age
Age plays a significant factor in the shape and development of the central sulcus. As we have already seen with age, both during the fetal stage and after birth, during the first few years of cognitive development, the central sulcus goes through a number of growth spurts.
It does not stop there. In adulthood, the sulcal span, which is the space between the anterior and posterior walls, will increase. On the other hand, age will lead to a decrease in the surface area of the walls. The length of the right posterior wall and convolution have both been observed to decrease.
Surface Area
The development of the central sulcus can even play a role in how our bodies work. The hand, a person, is likely to favor is thought to be determined by the structure of the central sulcus.
A larger central sulcus in the left hemisphere of the brain can be used as an indicator of a right-handed person, while a larger central sulcus in the right hemisphere of the brain can indicate a left-handed person.
There is additionally a central indentation found along the central sulcus, otherwise known as the 'hand knob,' which is also thought to provide visual evidence of which hand will be more dominant in a person.
Motor Function
As mentioned previously, the development of motor functions is also responsible for changes in the development and shape of the central sulcus. Quite simply, as the body develops and hones motor skills in terms of physical movement, the shape of the central sulcus will be affected.
The reason behind these shape changes is that the central sulcus plays such a critical role in acting as the division and separation between the primary motor cortex and the primary somatosensory cortex.
This means that as motor skills are developed and practiced, certain motor functions will influence how the central sulcus is shaped as both the primary cortex and the primary somatosensory cortex grow. In particular, the 'hand knob' position may be determined by specific motor functions.
This interrelatedness of the areas of the brain and how they affect the shape of the central sulcus also helps us understand how problems and abnormalities in the central sulcus can lead to cognitive and clinical disorders.
How Abnormality Of The Central Sulcus Causes Complications
If there are abnormalities during the early development of the central sulcus, these can lead to problems in the neighboring cortex, which can lead to issues with motor abilities, disability and increased danger of stroke and dementia.
Complications Of The Central Sulcus
The following are the complications that may arise from an abnormal central sulcus.
- ADHD (Attention deficit hyperactivity disorder)
- Williams syndrome
- SVD (Cerebral small vessel disease) and CAA (Cerebral amyloid angiopathy)
ADHD (Attention Deficit Hyperactivity Disorder)
ADHD has become more well-known and researched over the past few decades. With ADHD being linked to sensorimotor problems, the proximity of the central sulcus to the somatosensory and primary motor partitions of the brain has encouraged further research.
This research has yielded the discovery that persons who suffer from ADHD will usually display both a thicker cerebral cortex and a deeper trench of the central sulcus. A further finding has identified an abnormality in the shape of the center of the central sulcus in children diagnosed with ADHD.
Williams Syndrome
Williams syndrome is known to be a genetic disorder that displays as a mild intellectual disability, amongst other complications. The shape of the central sulcus is thought to play a role in this disability. Those with Williams syndrome have an abnormally shaped central sulcus with the dorsal end of the central sulcus being affected. The dorsal area of the central sulcus will most likely display as shortened.
SVD And CAA
(SVD) Cerebral small vessel disease is a group of diseases where the small blood vessels of the brain are diseased and can no longer function correctly, and this has a knock-on effect on larger blood vessels.
CAA (Cerebral amyloid angiopathy) is one of a number of this group of diseases and is where amyloid proteins gather in the small arteries of the brain, causing problems. This disease can cause stroke and dementia.
These small vessel diseases are linked to the central sulcus as persons who suffer from these diseases display marked damage in the area of the central sulcus.
Conclusion
The central sulcus is one of the more easily located sulci of the brain. It is the central lateral furrow of the cerebral cortex and, along with other sulci and gyri, serves to increase the overall surface areas of the cerebral cortex. The central sulcus starts developing at 8 weeks and continues to develop into adulthood.
In addition to assisting in providing a greater surface for grey matter, the central sulcus separates the somatosensory cortex from the primary motor cortex. This proximity to the motor centers of the brain has influenced its shape as well as made any abnormalities found in its structure useful markers for several complications.
