Wednesday, May 25, 2022

Why Do Brains Have Wrinkles

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The Brain Is Wrinkled How Does It Get It

Why do we have Wrinkles in our Brain?

The magnificent scale of the cerebral cortex and its folds, evident as bumps and furrows on its outer surface, is one of the most important characteristics of our cortex. Most animals with a large brain have a folded cortex, as we have mentioned, whereas most species with a tiny brain have a flat cortex, without folding.

The cerebral cortex is a laminar tissue where neurons converge at the surface and much of the cable that connects neurons between areas of the brain is contained in the bottom or inner portion.

In large brains, this layer of neural tissue that covers the outside of the brain is disproportionately larger than the deep brain structures it covers, and instead of assuming a balloon-shaped conformation, it folds back on itself, minimizing overall volume of the brain and skull.

It has been shown that the basal radial glia , regulated by intrinsic and extrinsic factors, plays a fundamental role in the tangential expansion of the cerebral cortex.

Thus, bRG is an essential requirement, although not sufficient, to generate a cortex with gyrations, since it provides new radial processes by which neurons migrate radially, thus spreading tangentially and expanding the cerebral cortex.

Gyrification During Human Brain Development

As fetal development proceeds, gyri and sulci begin to take shape with the emergence of deepening indentations on the surface of the cortex. Not all gyri begin to develop at the same time. Instead, the primary cortical gyri form first , followed by secondary and tertiary gyri later in development. One of the first and most prominent sulci is the lateral sulcus , followed by others such as the central sulcus, which separates the motor cortex from somatosensory cortex . Most cortical gyri and sulci begin to take shape between weeks 24 and 38 of gestation, and continue to enlarge and mature after birth.

Bizarre Human Brain With No Wrinkles Discovered

While photographing shelves of human brains stored away in a closet at the University of Texas for his next book, Adam Voorhes happened upon a truly unique find: a brain with no folds.

David Dexter, scientific director at Parkinson’s UK Brain Bank, told New Scientist that he had never seen an adult brain like this before: “We do get the odd individual where certain sulci are missing but nothing to the extent of this brain.

The lack of grooves and folds that characterize a human brain are due to a rare condition called lissencephaly. The disorder is caused by abnormal neuronal migration during embryonic development.

Image Credit: Adam Voorhes. Book: Malformed: Forgotten Brains of the Texas State Mental Hospital. The smooth brain is on the bottom, second to the right.

To learn more about this rare find, Voorhes spent over a year trying to hunt down the details of this and the approximately 100 other human brains in the collection. He sifted through a centurys worth of documents and found a history rife with battle for ownership of the collection. However, nothing about the specific individual came to light.

People with similar though less extensive forms of lissencephaly often experience difficulty swallowing, muscle spasms, seizures, and learning difficulties. Many individuals with this condition die before the age of 10.

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Children With Autism Have Brains That Fold Differently To Everybody Else’s

Recent studies have shown that the deep folds and wrinkles that make our brains look like giant walnuts don’t form in quite the same way in individuals diagnosed with autism – and this could help explain why it’s such a complex spectrum.

Autism condition is more accurately described as autism spectrum disorder , a term that covers a broad range of loosely related traits including a tendency to be overwhelmed by stimuli and difficulties in developing certain social skills.

On top of that, ASD seems to predominantly affect more boys than girls, which in part could be explained by variations in the thickness of the outer part of the brain – the cerebral cortex.

Now we have more reason to believe that the structure of the brain’s top layer might play a significant role in turning autism into an incredibly complex disorder.

A pair of studies analysing neural scans taken of young children and adolescents have detailed the structural development of their growing brains, finding large-scale differences.

Our cortex does a lot of the heavy lifting in our thinking and reacting, controlling everything from our reasoning to communication. To neatly cram all this real estate into our skulls, the grey matter ripples into ridges and crevices called gyri and sulci.

We can measure the development of these neural tissue folds as changes in the local gyrification index : a ratio comparing the area inside the sulci with the smooth outer surface.

Circumvolution Or Fusiform Gyrus

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The gyrus, or fusiform gyrus, is situated between the lower temporal gyrus and the hippocampal gyrus on the basal surface of the cerebral hemisphere, primarily in the temporal lobe.

This fissure is part of the limbic system, essential for affective processing and plays a vital role in facial recognition prosopagnosia, also called face blindness, can be caused by damage to this region of the brain

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Stimulate Neurogenesis With Physical Exercise

Any kind of physical exercise is good for your brain and mental health, but, so far, the evidence points to sustained, moderate-intensity, aerobic exercise as the best for growing new brain cells.

This includes exercises like jogging, biking, hiking, power walking, or swimming.

Harvard Medical School psychiatrist Dr. John Ratey, author of , is a leading authority on how exercise impacts the brain.

Ratey recommends performing aerobic exercise according to this routine for maximum cognitive benefits:

  • Sprint for 30 to 40 seconds.
  • Exercise at a gentle pace for 5 minutes.
  • Repeat for a total of 5 cycles.

If possible, exercise outdoors.

Researchers have noted a strong correlation between the production of BDNF and sunlight.

BDNF levels in humans vary widely with the seasons, with the highest concentrations occurring in spring and summer and the lowest during fall and winter.

If aerobic exercise sounds too demanding, theres a less strenuous alternative.

Mind-body exercises, such as yoga, can increase new brain cell production in the hippocampus.

They also reduce stress, a known disruptor of brain cell regeneration.

Do We Have The Most Neurons Predictions For Other Large

The different cellular scaling rules that apply to rodents and primates strongly indicate that it is not valid to use brain size as a proxy for number of neurons across humans, whales, elephantsand other large-brained species belonging to different mammalian orders. One consequence of this realization is that sheer size alone, or in relation to body size, is not an adequate parameter to qualify, or disqualify, the human brain as special.

A comparison of expected numbers can nevertheless be very illuminating. For instance, given the cellular scaling rules that we have observed for rodents , a hypothetical rodent brain with 86 billion neurons, like the human brain, would be predicted to weigh overwhelming 35kg a value that is way beyond the largest known brain mass of 9kg for the blue whale, and probably physiologically unattainable. As mentioned above, a generic rodent brain of human-sized proportions, weighing 1.5kg, would have only 12 billion neurons: in this sense, therefore, being a primate endows us with seven times more neurons than would be expected if we were rodents. Notice that this remarkable difference does not rely on assumptions about how brain size or cellular composition relate to body size in the species.

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Absence Of Receptors Promotes Brain Folds

A combination of laboratory tests and computer simulations showed how the mouse brain developed its folds. Due to the absence of FLRT1/3 receptors, the migrating young neurons did not adhere to each other as strongly as before. In this way, repellent mechanisms in the neighbouring cells probably gained the upper hand and forced the neurons to cluster into groups, explains Daniel del Toro, one of the two first authors of the study. Within these cell clusters, the neurons were able to move more freely and, as a result, they were also able to migrate faster to the outer layers of the brain. Due to this altered migratory behaviour, the neurons arrived too early in the cortex and no longer distributed regularly. The scientists assume that the resulting crowding in the upper cell layer increased the pressure in this layer, and this was alleviated through the formation of folds. The missing attraction forces between the neurons made the cortex softer and more malleable, and this probably benefitted the formation of folds as well, adds Tobias Ruff, co-first author of the study.

SM/HR

Brain Sizes In The Animal Kingdom

Episode 5 | Neuroscience | Why Do Brains Have Wrinkles?

This cortical folding is designed to make the brain more efficient thus allowing us to get smarter. If you look at the animal kingdom, then youll see that smarter animals have a denser brain in relation to their size. Elephants have far bigger brains than humans, but thats because they have much larger bodies which require far more coordination when moving around and keeping alive. If you were to compare the human brain to another animal our size like the chimpanzee you would find that our brains were much heavier which indicates more intelligence and a greater capacity for higher order thought.

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Brains Slightly Wrinkled Or With Too Many Wrinkles

The wrinkles present in the human brain are balanced considering the size and thickness of the cerebral cortex, but there are certain conditions in which these grooves and gyros are not arranged as they should.

Those who suffer from polymicrogyria, a genetic condition, have a brain with excess folds given by shallow furrows. This causes psychomotor retardation, neuronal damage and epilepsy.

Another condition in Pachygyria, characterized by excessively thick folds. This congenital malformation causes delays in development, seizures and a shorter life expectancy.

Are there brains without wrinkles?

It is interesting to mention that in nature, most brains are smooth. In general, animals with large brains such as dolphins or elephants have wrinkled brain cortices, while animals with small brains such as rabbits or rats have small, smooth brains.

In humans, a smooth or lissencephalic brain is the product of a malformation caused by defects in embryonic development. This study, carried out by researchers at Harvard, is valuable in understanding how the brain develops and what happens when it does not develop properly, leading to brain disorders.

Assumption : Proportions And Relative Size Matter

An often cited argument in favor of the uniqueness of the human brain is its relatively large cerebral cortex, which accounts for 82% of brain mass. Within this large cerebral cortex, a relative enlargement of the prefrontal cortex was once considered a hallmark of the human brain, but this view has however been overthrown by modern measurements . Still, the distribution of cortical mass in humans may differ from that in other primates, endowing particularly relevant regions such as area 10 with relatively more neurons in the human cortex .

As it turns out, however, the underlying assumption that the relative size of a brain structure reflects the relative number of brain neurons that it contains is flawed.

Now that numbers of neurons are available across rodents, primates and insectivores, we find that the cerebral cortex, despite varying in relative size from 42% to 82% of brain mass , contains between 13 and 28% of all brain neurons in 15 of 18 species studied, ranging between 13% and 41% . Most importantly, this fractional number of neurons in the cerebral cortex relative to the whole brain is not correlated with the relative size of the cerebral cortex .2). Instead, the number of neurons in the cerebral cortex increases coordinately with the number of neurons in the cerebellum .

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Circumvolution Or Cingulate Gyrus

An arch-shaped fissure or fold of the brain, situated over the corpus callosum, is the cingulate gyrus. Its primary function is to encourage as a connection or bridge between the limbic system and the neocortexs higher cognitive functions, which is why it plays a crucial role in connecting volitional, motor, memory, cognitive and affective aspects.

What Is The Functional Advantage Of Having More Gyri And Sulci

Why does our brain have wrinkles? Discover it!

They raise the cerebral cortexs surface area and form brain divisions. Growing the brains surface area allows more neurons to be crammed into the cortex so that more information can be processed.

In this post we are going to answer Why does the brain have gyri and sulci? We described each gyri and sulci in the brain, how they are formed and why they are important.

If you have any questions or comments please let us know!

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How Does Our Brain Fold Study Reveals New Genetic Insights

Date:
RMIT University
Summary:
Problems with brain folding are linked with neurological conditions like autism, anorexia and schizophrenia, but there are currently no ways to detect, prevent or treat misfolding. New research offers genetic insights into the folding process, an important step towards developing potential treatments.

New research is helping unlock the mystery of how the brain folds as a baby develops in the womb — a process critical to healthy brain function.

Misfolding of the brain is linked with many neurological conditions including autism, anorexia, epilepsy and schizophrenia.

Premature birth and fetal growth restriction, major risk factors for cerebral palsy, can also affect brain folding and lead to cognitive deficits.

While we know folds are essential to how a healthy human brain works, scientists are only beginning to understand what drives the folding process and why it goes wrong.

A new pre-clinical study by Australian and Swiss researchers has for the first time identified the genes linked with the development of the two types of brain folds — inward and outward — in the grey matter of the brain.

Using animal models that closely resemble human brain development, the study found differences in both genetic expression and neuron shape during the folding process.

“Our study is a critical step towards fully understanding those genetic instructions, by pinpointing which genes are linked with fold development.

Folding fundamentals

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Why Does The Brain Have Grooves

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You Get New Brain Wrinkles When You Learn Something. As the fetus grows, its neurons also grow and migrate to different areas of the brain, creating the sulci and gyri. By the time it reaches 40 weeks, its brain is as wrinkled as yours is . So we don’t develop new wrinkles as we learn.

Additionally, why is surface area important to the brain? By increasing the surface area in the brain, the brain has more room to carry out its functions within the space it has and can fit more neurons in the same amount of space.

In this way, what are the crevices in the brain called?

The wrinkles in your brain can either be crevices, known as sulci, or ridges between crevices, which are known as gyri. The folding of the cortex allows more brain area to fit into a smaller space.

What is the advantage of the cerebrum of the brain being wrinkled?

Our brains pack extra real estate there with additional folds. Wrinkles also help larger brains keep their white matter fibers that link different areas of the cortex in order. As brains grow larger, white matter fibers must stretch longer.

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What Does A Wrinkly Brain Mean

The main reason why the human brain is wrinkled is that folding in on itself allows it to gain some space. The brain folds are what are called, more appropriately, convolutions, while the furrows or fissures are the depressions between these wrinkles.

Today we wanted to continue looking for answers and the question we asked ourselves in this article is the following: Why does the brain have wrinkles? We found out why the brain looks so strange and why its folds are so important.

If you have any questions or comments please let us know!

The National Institute Of Neurological Disorders And Stroke

TIL: Why Your Brain is Wrinkly | Today I Learned

Since its creation by Congress in 1950, the NINDS has grown to become the leading supporter of neurological research in the United States. Most research funded by the NINDS is conducted by scientists in public and private institutions such as universities, medical schools, and hospitals. Government scientists also conduct a wide array of neurological research in the more than 20 laboratories and branches of the NINDS itself. This research ranges from studies on the structure and function of single brain cells to tests of new diagnostic tools and treatments for those with neurological disorders.

For information on other neurological disorders or research programs funded by the National Institute of Neurological Disorders and Stroke, contact the Institute’s Brain Resources and Information Network at:

Office of Communications and Public LiaisonNational Institute of Neurological Disorders and StrokeNational Institutes of HealthBethesda, MD 20892

NINDS health-related material is provided for information purposes only and does not necessarily represent endorsement by or an official position of the National Institute of Neurological Disorders and Stroke or any other Federal agency. Advice on the treatment or care of an individual patient should be obtained through consultation with a physician who has examined that patient or is familiar with that patient’s medical history.

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Why Does The Brain Have Ridges

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Explanation: The ridges are called Gyri and the grooves are called Sulci. The main function of these ridges and grooves is to increase the surface area of the cerebrum such that it can accommodate more number of neurons.

Subsequently, question is, do you get a wrinkle in your brain when you learn? You Get New Brain Wrinkles When You Learn Something. As the fetus grows, its neurons also grow and migrate to different areas of the brain, creating the sulci and gyri. By the time it reaches 40 weeks, its brain is as wrinkled as yours is . So we don’t develop new wrinkles as we learn.

Considering this, why does the brain have folds?

Gyrification is the process of forming the characteristic folds of the cerebral cortex. Gyrification allows a larger cortical surface area and hence greater cognitive functionality to fit inside a smaller cranium. In most mammals, gyrification begins during fetal development.

What is the advantage of the cerebrum of the brain being wrinkled?

Our brains pack extra real estate there with additional folds. Wrinkles also help larger brains keep their white matter fibers that link different areas of the cortex in order. As brains grow larger, white matter fibers must stretch longer.

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