Knowing how the brain develops into its folded shape could help scientists better explain what happens in people with congenital conditions such as polymicrogyria (a condition characterized by an excessive number of folds), pachygyria (a condition with unusually thick folds) and lissencephalia (a smooth brain condition, without folds).
Historically, there have been three broad ideas about how gyri and sulci develop. One idea is that some areas of the cortex simply grow more and rise above other areas, creating the gyri. Another idea is that groups of highly interconnected neurons in the cortex are mechanically pulled close to each other by the threadlike axons that make up the white matter. However, evidence suggests that neither of these two ideas is correct.
The third idea is that the gray matter grows more than the white matter, leading to a "buckling" that gives the cortex its shape, the researchers said.
But earlier attempts to model this buckling were not successful, the researchers said. In previous studies, researchers assumed that the gray matter is a thin, stiff layer growing atop of a thick, soft base of white matter, but this assumption yielded wrinkles that aren't like the ones in real human brains.