Sulcus (neuroanatomy)

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 divide the two hemispheres - the interhemispheric fissure - is very rarely called a "sulcus".

Individual variation
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.

Gyrification across species
The variation in the amount of fissures in the brain ("gyrification") between species is more related to the overall size of the animal rather than the encephalization. That is, large animals have many sulci:
 * ''"[L]arge rodents such as beavers (40 pounds) and capybaras (150 pounds) have many more sulci than smaller rodents such as rats and mice - but also more fissures than smaller monkeys".

Notable sulci

 * Lateral sulcus
 * Central sulcus
 * Postcentral sulcus
 * Precentral sulcus
 * Cingulate sulcus
 * Superior frontal sulcus
 * Inferior frontal sulcus

Macaque
A macaque has a more simple sulcal pattern. In a monograph Bonin and Bailey list the following as the primary sulci :
 * Calcarine fissure (ca)
 * Central sulcus (ce)
 * Sulcus cinguli (ci)
 * Hippocampal fissure (h)
 * Sulcus intraparitalis (ip)
 * Lateral fissure (or Sylvian fissure) (la)
 * Sulcus olfactorius (olf)
 * Medial parieto-occipital fissure (pom)
 * fissura rhinalis (rh)
 * Sulcus temporalis superior (ts) - this sulcus runs parallel to the lateral fissure and extends to the temporal pole and often superficially merges with it.