According to a faculty member at the University of Washington, gyri and sulci arose as a way to pack more brain volume within the finite dimensions of the skull. The larger the surface area of the brain, the more neurons it can hold. Therefore, many highly intelligent animals have evolved wrinkled brain surfaces that increase the relative surface-to-volume ratio.
The gyri and sulci are composed of grey matter, one of the primary types of brain tissue. The University of Washington explains that the fissures or crevices are called sulci. The bumps or raised areas between the sulci are called gyri. Each person has a unique combination and pattern of sulci and gyri. Because of these wrinkles, the human brain has approximately 324 inches of surface area, which is about the same amount of surface area of a piece of large newspaper.
The University of Washington contends that the gyri and sulci help to divide the cerebrum into four basic lobes, or sections. The occipital lobe is located at the rear of the brain, while the frontal lobe is located at the front of the brain. The temporal lobes occur along the sides of the brain, while the parietal lobes are located along the top of the brain.