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The simple physics of how the brain gets its intricate folds

Brian Resnick is Vox’s science and health editor, and is the co-creator of Unexplainable, Vox's podcast about unanswered questions in science. Previously, Brian was a reporter at Vox and at National Journal.
This is the weirdest, coolest science experiment I've seen in some time.
Mahadevan Lab/Harvard SEAS)

The human brain is so powerful not because it is so large — but because the wrinkles on it give it a large surface area. But what's long been a mystery is how the brain's wrinkles actually form.

The brain model seen in the GIF above — in all its mesmerizing and creepy glory — recently gave researchers at Harvard some insight.

This isn't a real brain. It's a gel brain 3D-printed in a lab, meant to demonstrate how, in the womb, this wrinkling — called gyrification — might occur. The researchers theorized that the folds form because the outside of the brain grows quicker than the inside of the brain, causing it to fold inward.

The shape for the 3D print is based off the brain of a 22-week-old fetus. The researchers then placed that smooth, gel brain in a solution that swells the outermost layer of the gel to simulate the growth that happens in the womb.

Remarkably, the results look very similar to a fully developed baby brain.

Mahadevan Lab/Harvard SEAS

Here, they compare the folds on their lab-grown brain (bottom right) with a real one (bottom left).

That they were able to reproduce the brain's folds on the gel model gives weight to the hypothesis: that brain development can be explained by simple physics.

"Our physical gel model shows that we can capture the qualitative features of the folding patterns ... setting the stage for how biology can build on this simple physical pattern-forming instability," the authors write in their paper, published in the journal Nature Physics.

This isn't the final word on fetal brain development. "There could be some other biological factors that modulate this process," Tuomas Tallinen, one of the study's co-authors, told the BBC.