Humans are very smart animals thanks to our big, meaty brains. The human brain is distinct from those you find in most other creatures in that the surface is covered with undulating folds and ridges. Scientists have long puzzled over the mechanism by which these folds develop, and a new study points to simple physics as the cause. Using a gel model of a brain, researchers from Harvard were able to simulate 12 weeks of fetal brain development in about 20 minutes.
The wrinkled outer layer of the brain, known as the cortex, is where higher brain functions take place. The folds increase surface area dramatically, but it has been unclear if the folds were formed by a biochemical process, physical properties, or something else. To find out, the experiment started with a model of the 22-week fetal brain, which is smooth and doesn’t look anything like we expect a brain to look. Then, a second layer was applied that expands when exposed to a solvent.
The mock brain was placed in an organic solvent, and in the space of a few minutes, the outer layer began exhibiting the characteristic folding of the cortex. When the pattern was examined, the team found it was a startlingly close match for a real brain at about 34 weeks of development. That indicates most of the development of folds in a brain might be a simple consequence of physics.
A real brain doesn’t stop at 34 weeks, of course. Cortical area increase by about 20 times during development, which can’t be replicated in a simple physical model like this. However, the team did use the two layer design of its gel brain to create a computer simulation around it. By allowing the simulated outer layer to expand, it developed ridges very much like an adult brain. This research holds promise for understanding neurological diseases that involve abnormal brain folding. If an artificial brain could be altered to recreate those imperfections, it could be a real boon to doctors.