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Why is the Brain Wrinkly?

By Dr. Usmarah Hussain

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Why is the Brain Wrinkly

The human brain is rightfully known as the most complex organ known to mankind. This apparently small structure houses approximately 86 billion neurons along with axon fibers covering several hundred thousand miles to connect them with each other. If you ever had time to take a closer look at the brain model, you’ll find that it’s not as smooth as most body organs are. The many folds and grooves spreading to all directions make it similar to that of a walnut.

Have you ever wondered why the brain is not like other smoother organs? What’s the reason behind all its wrinkles, and why do these wrinkles exist? Unsurprisingly, the folding process that gives rise to the characteristic bumps and grooves in the human brain is just as complex as its structure. Fortunately, with decades of dedication and research, experts are finally in a position to explain what causes this wrinkling and why it exists.

Keep reading the article to know more about why the human brain is so wrinkly, how these wrinkles are formed, and why we need them so badly.

The Mystery Behind a Wrinkly Brain: The Need for These Folds and Bumps

You have often seen people comparing the brain to a walnut, but have you ever wondered why the organ has so many folds and bumps? Why doesn’t it have a smooth, shiny surface just like the kidneys or the liver? Many people do not know that the deep folds that give their brain its characteristic walnut appearance is, in fact, Mother Nature’s solution to fit a large, extremely powerful processor into a small-sized skull.

We are all aware that neurons, the tiny cells in the brain, join together to form the organ and the rest of the nervous system. These neurons make the brain capable of performing every single task, no matter how small or big it is. The relationship between the number of neurons and brain function is linear. What this means is the larger the brain surface (cerebral cortex), the better the performance. So if you wish to have an efficiently working brain that controls everything in the body, it must have billions of neurons connected with each other and working optimally to keep you on top of your abilities. But the problem is, how do you fit so many neurons in such a tiny skull? That’s where the role of wrinkles and convolutions in the brain comes into the picture.

Like a piece of flat paper that you can crumple together to fit into a small hole, nature folds your brain and give it wrinkles during the development phase so that it can fit as many neurons as possible, giving you a chance to perform your best. Moreover, this folding also allows neurons to get packed close together with faster connections for enhanced brain activity. Some studies suggest that these brain convolutions help the organ acquire a surface three times greater than it would have without wrinkles. This concept of brain wrinkling and its purpose is supported by the fact that many animal species, with little chance of learning, lack these convolutions. Known as lysencephalics, these species find it more difficult to learn and carry out higher cognitive functions than humans and other species with brain wrinkles.

 So now we finally know the reason behind having a convoluted brain, and we are certainly thankful for it. This takes us to the next question that might pop into your wrinkly brain: how does the brain acquire these folds and grooves?

The Mechanism of Brain Wrinkling Unleashed

In recent years, scientists have been investigating the association between the growth and folding of the brain and mechanics, the forces that object exert on each other. Another possible reason put forward by experts is the differential tangential growth that has been found to support brain folding and wrinkling. The proponents of this theory believe that the outer layer of the brain grows more rapidly than the inner layer due to the way neurons grow and migrate during fetal development. These mismatched growth rates exert a higher amount of pressure on the outer layer, forcing it to fold onto itself to release this instability.

To better explain the mechanism of brain folding, experts conducted a research study where the developed a mechanical model of the brain whose outer layer had a greater growth rate than the inner one. [1] Due to this mismatch, the inner layer blocked the spread out of the outer layer, forcing it to fold and buckle in an attempt to stabilize its structure. The findings of this study were further confirmed by another research that used a 3D-printed brain model to show how mismatched growth rates resulted in brain folding. [2] Experts conducting these studies further confirmed that brain buckling maximizes the surface-to-volume ratio in the brain, allowing it to pack in more neurons compared to the space it has while reducing the relative distance between them. Since then, many other mechanical factors have been found to determine the eventual shape a brain acquires, such as the initial thickness of the outer layer and the relativeness stiffness of the two layers.[3]

More recent studies have revealed the role of axons in regulating the folding process in the brain. Axons are part of a neuron that allows it to transmit electrical signals to nearby cells. As per experts, the brain areas where the axonal number is high form ridges, whereas valleys form in areas with low axonal densities. These findings confirm the importance of axon density in determining how the brain will look like once it completes its developmental stage. The process of forming more sophisticated brain models based on neuroimaging of the real brain still continues, and experts are determined to provide the world with more useful information about brain development.[4]

Too Little or Too Many Wrinkles: How it Affects the Brain

Experts have discovered many different types of brain disorders, many of which exist due to abnormal brain development. The existence of such diseases highlights the role the brain structure plays in its proper functioning. Because wrinkles form an important part of the brain structure, can having too many or too few of these folds mess with normal brain function? The answer is yes, it can.

To understand the problems associated with abnormal wrinkling, it is important to remember that the human brain comprises an outer layer and an inner layer. The outer layer is known as gray matter, whereas the inner layer is called white matter. Both types of matter connect with each other through axonal pathways that connect the neurons making up these layers. Anything that messes with the wrinkling and convolutions of gray and white matter and the axonal pathways connected to them can lead to severe neurological disorders. Let’s look at the two most common types of brain disorders associated with how the organ wrinkles.


In some people, the outer layer of the brain is naturally thicker than usual, which makes it difficult for the organ to form an adequate number of ridges and valleys. This results in a condition called lissencephaly, or a smooth brain with no brain fold or wrinkles. Experts describe lissencephaly as a condition in which certain areas of the brain where there are usually clefts and folds become smooth. [5] These malformations severely disturb the development of the rest of the nervous system, leading to psychomotor and cognitive impairments.

The problem begins during intrauterine fetal growth, where the cerebral cortex fails to fold back on itself. As a result, the volume of nerve tissue that can fit inside the skull greatly reduces, and the brain eventually acquires a homogenous appearance. The intensity of brain smoothing in lissencephaly can vary, depending on what caused it.

Although rare, lissencephaly can lead to dire consequences for the mental and physical dependence of a person. In severe cases, the disease completely affects intellectual functioning, whereas, in others, these deficits might be minimal. Regardless of the severity, the life expectancy of people with lissencephaly is usually around 10 years, and most victims are eventually due to reasons like respiratory issues, choking, or epileptic seizures.


Polymicrogyria is opposite to lissencephaly. It happens when the brain’s outer layer is thinner than usual and results in excessive folding. [6] People with polymicrogyria can experience mild to severe neurological issues like paralysis, developmental delays, and seizures. Other symptoms may include:

  • Recurrent jerkiness
  • Muscle weakness
  • Problems with swallowing
  • Speech-related issues
  • Crossed eyes

Polymicrogyria can be unilateral (one-sided) or bilateral (two-sided) and localized or generalized depending on the areas of excessive folding. Generalized bilateral polymicrogyria is the most severe form, which affects the entire brain leading to severe intellectual disability and other symptoms that are difficult to control with medicines. While the condition usually occurs as an isolated problem, it sometimes accompanies other brain abnormalities and may present as a feature of many genetic syndromes.


Thanks to ongoing research, we finally have the answers to why our brains resemble a walnut. It turns out that these wrinkly grooves and valleys have much more to do than giving our brain its characteristic look. In fact, this folding process is what differentiates us from other species in terms of learning and cognition. While experts have provided us with many possible explanations of how and why brain folding and wrinkling take place, there is so much more to discover in due time.

Frequently Asked Questions

Why is it so important to have wrinkles in the brain?

When it comes to the human brain and intelligence, a direct relationship connects the two together. The greater the surface area of the brain, the higher the intelligence level. Having wrinkles and folds in the brain allow the organ to have a larger surface area for higher intelligence but without occupying too much space so that it can easily fit the skull. Compare it to a piece of paper that you can crumple to fit in a smaller hole. Just like that, the wrinkles of the brain allow the organ to have more neurons fitted inside the limited size of the skull for greater function.

How did the brain get so many folds?

Experts believe that the outer part of the brain, known as the cerebral cortex, undergoes rapid, differentiated growth, forcing the gray matter to grow faster than the white matter. As a result, folds form on the external surface.

Does having more wrinkles mean more smartness?

Because wrinkles allow more neurons to adjust within the brain, thicker wrinkles are usually associated with higher IQ levels.


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