Thread by @R3RT0

Brain folds develop together with cytoarchitectonic regions and corticocortical connections. That folding results from a mechanical instability is now relatively well accepted. However, the pattern of these folds is still thought to reflect patterned gene expression #ohbmx

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Indeed, a genetic program could encode regionalisation, connectivity and folding patterns. But what if folding *patterns* were of mechanical origin too? That would mean that mechanics have a causal role in the development and evolution of brain organisation! #ohbmx

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One hint at the mechanical origin of folding patterns comes from observations made across primate species. Brains of phylogenetically distant species but with similar volume tend to have similar folding patterns despite their common ancestor being likely lissencephalic #ohbmx

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What could be the mechanism? We investigated whether an idealised model could produce stable folding patterns. The mechanics & initial smooth geometry of our model mimicked newborn ferret brains. The neocortex in our model grew homogeneously – no patterned growth! #ohbmx

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Despite its simplicity, the folding pattern captured traits of real ferrets. Ferret brains are elongated: real & ideal folds followed this axis. Overall, many specific ferret sulci could find their counterpart in our simulations #ohbmx

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Mechanical forces have strong and varied effects on the developing tissue, influencing cell proliferation, apoptosis, cell fate, shape and pathfinding. The mechanical forces induced by brain folding could then have a causal effect on the organisation of the neocortex #ohbmx