Surprisingly, the natural folds and toughs of the human brain are uncommon in the rest of the animal kingdom, only shared by dolphins, some primates and a few other animals. Scientists have understood for years why the human brain is folded, but have up until recently had no idea how a fetal brain folds.
[Image Source: Harvard]
From an anthropological viewpoint, it is advantageous to have a folded brain, as this means a greater surface area accompanied by less distance between cells. The folds of the brain start developing in the 20th week of pregnancy, and continue until a child is about a year and a half. There have been many ongoing theories of how the human brain develops, but none have been able to be scientifically tested, until now.
Researchers from the Harvard John A. Paulson School of Engineering and Applied Sciences along with scientists from France and Finland have found a method to demonstrate their theory of how a folded brain develops. A realistic gel model of a fetal brain based on MRI images was developed, then coated in a thin layer of an elastomer analog. This outer layer of elastomer gel symbolizes the cortex, with the inner layer serving as the basic brain structure. The entire brain model was then placed in an aqueous solution, allowing the outer gel (cortex) to absorb the solvent. Rapid physical expansion occurred in the outer layer creating mechanical compression forces, which creates folding.
[Image Source: Harvard]
It was also noted that the initial geometry of the brain structure is important as it orients the mechanical folds. Main areas of the brain are defined through this essential brain folding, being one of the main reasons this finding is so important.
“Brains are not exactly the same from one human to another, but we should all have the same major folds in order to be healthy," said researcher Jun Young Chun.
Through the study of the brains folding, scientists may be able to predict developmental disorders and determine how specific brain structure is related to human progression. On top of creating a physical model of a 22-week-old fetal brain, researchers designed a computer model to demonstrate the same principles, seen below. The folds seen in the fetal brain model aren't random either, in fact, they closely resemble different regions of a real human brain.
It is important to note that this test only proves theories of how the brain folds and does not serve as an example of how a brain grows in size during fetal growth. From here, the research can transition into a deeper study of the dynamics of the human brain, possibly leading to further advances. The researchers who carried out the test are still incredibly shocked at how well their model resembled an actual brain in both growth and structure.