How does the brain get its walnut like wrinkles?

The deep folds in the brain’s cerebral cortex or more popularly known as the grey matter are mother nature’s way of fitting something very large and powerful in a limited space. These folds give the brain a walnut like appearance and allow the brain cells (neurons) to be packed efficiently and remain in close contact for efficient and speedy connections.

Scientists have known for many years why these folds are present, but how they appear has always been a mystery. Recently, a team of researchers from the United States and Europe said the folds can be explained by physics - a discovery that may have important implications for understanding certain brain disorders.

Folds in the cortex develop through buckling in weak spots which develop as the foetal brain grows.The brains of human foetuses are smooth for about the first 20 weeks, when folding begins and continues until the child is about 18 months old. The position, size and number of neurons during brain growth lead to expansion of the grey matter relative to the underlying white matter.

This puts immense pressure on the cerebral cortex leading to mechanical instability that causes it to crease locally. This simple evolutionary innovation allows for the thin but expansive cortex to be packed into a small volume, and is the dominant cause behind brain folding.