The supremacy of the human brain is due in large part to its topography. Humans, along with a small handful of other species (including pigs, whales, and primates), have brains that have a cortex – the outer layer of the brain – which folds in on itself and becomes “wrinkled” in early development. This wrinkling of the cortex is critical for delivering more cortical surface area, and hence more computational thinking power. And while it was previously thought that this wrinkling was due to genetic or cellular influences, thanks to a new 3-D printed silicone “brain,” researchers now believe that the folds actually occur mechanically.
In order to demonstrate how our brains’ cortical folds develop, a team at Harvard University built a 3-D printed “brain” out of a silicone-based gel, based on MRI scans of fetal brains. They then covered that silicone brain (which looks like it has the color and texture of uncooked chicken), with another thin layer of gel, which swells when it absorbs solvent. They then placed this dual-layered brain in solvent, and monitored how the expansion of the outer layer affected the brain beneath it. And sure enough, as the outer layer expanded, it forced the inner brain to contort and fold in on itself, just like a real brain.
Above, you can watch a time-lapse video of the silicone brain developing trademark cortical folds as it’s constricted by the outer layer of gel, which is expanding as it absorbs solvent. This is an important experiment and discovery, because it demonstrates that the folds developed by our brains are not due to genetic or cellular causes, but simply mechanical pressures during development.
A more in-depth look at the steps of the experiment are outlined in the video below:
What do you think about this 3-D silicone brain? Let us know in the comments section below!
Image: Mahadevan Lab/Harvard University