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Gray's Fig. 726– Lateral surface of left cerebral hemisphere, viewed from the side.

Gray's Fig. 727 - Medial surface of left cerebral hemisphere.

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".

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^[1]. 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 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"^[2].

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

A macaque has a more simple sulcal pattern. In a monograph Bonin and Bailey list the following as the primary sulci^[3]:

• 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.

• Sulcus (anatomy)

1. ^ Ono, Kubick, Abernathey, Atlas of the Cerebral Sulci, Thieme Medical Publishers, 1990. ISBN 0-86577-362-9. ISBN 3-13-732101-8.
2. ^ Martin I. Sereno, Roger B. H. Tootell, "From Monkeys to humans: what do we now know about brain homologies," Current Opinion in Neurobiology 15:135-144, (2005).
3. ^ Gerhardt von Bonin, Percival Bailey, The Neocortex of Macaca Mulatta, The University of Illinois Press, Urbana, Illinois, 1947

• Visual explanation of gyri, sulci, and fissures

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