All ingenious – is simple. It happened with the extremely difficult task of neurophysiology on the development of folding of the cerebral cortex. After years of study, scientists finally managed to create a mathematical model of folding, which miraculously coincided with the model of a crumpled sheet of paper, writes likar.info.
A simple answer to a difficult question
What is common between the brain and the crumpled sheet of office paper? Parallels not so much, but a crumpled ball of paper has helped to solve one of the most intriguing problems related to the development of the human brain. As it turned out, the mammalian brain develops like a crumpled sheet of paper that describes a mathematical function.
“This is a truly brilliant study, which allowed us to make significant progress in the understanding of scientists of how the brain develops,” says neuroscientist from the University of California in San Francisco Arnold, Krigstein.
The study also sheds light on the mechanisms underlying some structural disorders of the brain, and can help in the future in the creation of a specific therapy to relieve the symptoms of these diseases.
The cortex of the brain and its mysteries
The cortex of the human brain is a complex wrinkled landscape with its “ridges” called gyri and “valleys”, called furrows. There is a clear advantage of this cortical folding. The presence of more subtle, complex crust means that the transmission of information from one point to another covers a smaller distance and can happen much faster.
Gyrus and sulcus occur in humans during the third trimester of pregnancy. For a long time remained a mystery, what forces are behind in their education. According to a neurologist from the Federal University of Rio de Janeiro’s Suzanne Herculano-Souzel for a long time was dominated by two explanations regarding the mechanisms of formation of the folded structure of the cerebral cortex, but they were mutually exclusive.
The first hypothesis was that the larger the brain, the more complex and folded his bark. However, this hypothesis failed to explain the specific structure of the brain in some animals, for example, the manatee. Despite the fact that the brain of the manatee is almost the same size as a baboon, the latter has a high degree of folding, while the brain of the manatee is almost entirely smooth. Cetaceans have also been a problem for this hypothesis. For example, the brain of a Dolphin is much smoother than the human brain, despite the fact that the brain of a Dolphin and human are almost the same size.
The second hypothesis was that the folding of the brain is due to the increase in the number of neurons. That is, it is nothing but a way to provide this increase in the number of neurons that is necessary for the development of higher nervous activity. Franz Gall, a neuro-scientist, in the 19th century suggested that the brain is complex so that a larger surface of the cortex could fit inside the space of the skull. An alternative theory suggests that the cortex expanded, like a balloon that eventually led to this folding.
This conjecture has many contradictions.Thus, the cortex of the human brain has three times more neurons than the neocortex of the elephant, but the mass of the human brain 2 times less ivory. In baboons and pigs are about the same level of folding of the brain, at the time, as baboons almost 10 times more neurons than in pigs. These contradictions indicate that different species have different mechanisms control the folding of the cerebral cortex. In other words, each species has its own way to control development of the cerebral cortex.
How is the cerebral cortex
For the simulation of the folding of the brain scientists have built a power function obtained from the product of the surface crust and the square root of the thickness of the crust. When one of the scientists looked at the schedule, then exclaimed, “It’s a sheet of paper!”. The researchers noticed that the same model that predicted the degree of folding of the brain also explains the folding of paper sheets. To test this theory, researchers just drew a linear dimension of crumpled sheets of paper.
This simple experiment you can conduct at home. Crumple a sheet of paper and put it on the table. You’ll see how a crumpled ball a little expanded, as it saves a certain amount of energy. However, in the end, he makes the final crumpled form that is most advantageous from the energy point of view after you applied the force to crumple it. This last conformation is the new condition of the ball. A minimum number of effective free energy. This is a condition in which the ball is most stable. Even when a crumpled piece of paper are not affected by external forces, he still keeps the ball shape. Like wrinkled paper, folded brain will not change its state.
As you know, more dense paper leads to fewer wrinkles when it is compacted. The same paradigm holds for the brain. Take three sheets of paper and crumple them as one sheet. This ball will be much larger due to the additional weight of the material.
Thicker cortex of the brain develops less and is made in the surface with fewer curves (convolutions and grooves). The model crumpled paper also shows that the larger surface area led to greater curtailment. The results show that the growth of the developing brain thickness and area of the surface of the fabric and the time affect how the brain develops.
The forces acting on the cerebral cortex
The forces acting on the paper come from the efforts of human hands, while the force applied to the cortex arise from several sources. For example, acting from the outside atmospheric pressure, which affects the cerebrospinal fluid. There is also the pressure exerted by the cells that form the brain. This combination of forces, as well as the thickness and surface area make the cerebral cortex to bend in the characteristic folds.
Study of crumpled paper gives some idea of how in the brain there are certain violations. For example, lissencephaly, which is a smoothing of the cortex, without any grooves or folds. The researchers came to the conclusion that this disorder occurs because of a violation of neuronal migration in the brain. No folding when this anomaly is explained by the fact that the cortex in this case is almost 4-5 times thicker than normal.