What are the folds in the brain called?

The folds in the brain are crevices called sulci and ridges called gyri, and several of them have specific names. Unfolding all the crevices and ridges would leave a human brain approximately the size of a pillowcase, according to How Stuff Works.

Additional gyri and sulci do not form when people learn, but changes in the brain do occur in the form of brain plasticity. This results in the addition of more synapses and blood cells that support neurons. The brain of a fetus is smooth and tiny, but it is as wrinkled as an adult brain by 40 weeks, as the neurons create gyri and sulci by growing and migrating to different parts of the brain.