In neuroanatomy, a sulcus (Latin: "furrow", pl. sulci) is a
depression or fissure in the surface of the brain. It surrounds
the gyri, creating the characteristic appearance of the brain in
humans and other large mammals. Large furrows (sulci) that
divide the brain into lobes are often called fissures. The large
furrow that divides the two hemispheres—the interhemispheric
fissure—is very rarely called a "sulcus". The sulcal pattern
varies between human individuals, and the most elaborate
overview on this variation is probably an atlas by Ono, Kubick
and Abernathey: Atlas of the Cerebral Sulci. Some of the larger
sulci are, however, seen across individuals - and even species -
so it is possible to establish a nomenclature. The variation in
the amount of fissures in the brain (gyrification) between
species is related to the size of the animal and the size of the
brain. Mammals that have smooth-surfaced or nonconvoluted brains
are called lissencephalics and those that have folded or
convoluted brains gyrencephali