The human brain is made up of a series of tightly folded lobes, and there is substantial evidence suggesting that the purpose of these folds is to increase surface area, allowing for more neural connections to form a complex network. According to a report from the LA Times, however, a recent Harvard study offers new insights into how the brain generates these folds – a distinctly human characteristic.

Human’s don’t even start do develop brain folds until they have been in the womb for about 23 weeks. Many species, like mice and rats, don’t have folds at all – their brains are smooth and pink.

According to Stanford researcher Ellen Kuhl, who was not a part of the recent study, “The findings have provided the first experimental evidence of the theory of differential growth and demonstrated that physical forces – not just biochemical processes alone – play a critical role in neurodevelopment. Their findings could have far-reaching clinical consequences for diagnosing, treating and preventing a wide variety of neurological disorders.”

So how did scientists find out exactly how the brain creates its folds? Why, they 3-D printed a fake gel brain to see how it developed, of course. Researchers have long believed that the process behind the brain’s folds was driven by biochemical reactions, but the new study reveals that it might be a little simpler than that.

According to Lakshminarayanan Mahadevan, a physicist and applied mathematician at Harvard, “I have a longstanding interest in trying to understand how the body or bodies of animals organize themselves. I approach these problems from a mathematical perspective.”

Researchers used magnetic resonance imagery from a human fetal brain at 22 week’s gestation, just before the folds were due to begin developing. They cast a fake brain out of gel with a 3-D model of the fetal brain, and covered it with a coat of rubbery gel to imitate the cortical tissue, know as gray matter, where the folds develop.

They found that the cortical tissue continues to grow while the white matter below remains a constant size. As the cortex grows, the tissue collapses in on the limited space it has, generating folds and creases to compensate for the lack of room.

The study has far-reaching implications for our understanding of how the brain develops and what can go wrong during this process. “Making these connections can help us identify topological markers for the early diagnosis of autism, schizophrenia or Alzheimer’s disease, and ultimately, design more effective treatment strategies,” said Kuhl.

A Harvard press release describing the details of the study can be found here.