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takyon [soylentnews.org] writes:

The physics of the folding process that creates the wrinkled surface of the human brain has been replicated using a gel model [bbc.com]:

Scientists have reproduced the wrinkled shape of a human brain using a simple gel model with two layers. They made a solid replica of a foetal brain, still smooth and unfolded, and coated it with a second layer which expanded when dunked into a solvent. That expansion produced a network of furrows that was remarkably similar to the pattern seen in a real human brain.

This suggests that brain folds are caused by physics: the outer part grows faster than the rest, and crumples. Such straightforward, mechanical buckling is one of several proposed explanations for the distinctive twists and turns of the brain's outermost blanket of cells, called the "cortex". Alternatively, researchers have suggested that biochemical signals might trigger expansion and contraction in particular parts of the sheet, or that the folds arise because of stronger connections between specific areas.

[...] Humans are one of just a few animals - among them whales, pigs and some other primates - that possess these iconic undulations. In other creatures, and early in development, the cortex is smooth. The replica in the study was based on an MRI brain scan from a 22-week-old foetus - the stage just before folds usually appear. A 3D printout of that scan was used to make a mould, which in turn was filled with a silicon-based gel to make the "gel brain". Finally, a 1mm-thick layer of slightly different gel was added to the surface - to play the role of the cortex.

On the growth and form of cortical convolutions [nature.com] (DOI: 10.1038/nphys3632)

Older study: Gyrification from constrained cortical expansion [pnas.org] (open, DOI: 10.1073/pnas.1406015111)

Original Submission