Latin Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally a dialect spoken in the lower Tiber area (then known as Latium) around present-day Rome, but through ...

: "furrow", pl. ''sulci'') is a depression or groove in the

cerebral cortex The cerebral cortex, also known as the cerebral mantle, is the outer layer of neural tissue of the cerebrum of the brain in humans and other mammals. The cerebral cortex mostly consists of the six-layered neocortex, with just 10% consisting o ...

. It surrounds a gyrus (pl. gyri), creating the characteristic folded appearance of the

brain A brain is an organ (biology), organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. It is located in the head, usually close to the sensory organs for senses such as Visual perception, vision. I ...

human Humans (''Homo sapiens'') are the most abundant and widespread species of primate, characterized by bipedalism and exceptional cognitive skills due to a large and complex brain. This has enabled the development of advanced tools, cultu ...

s and other

mammal Mammals () are a group of vertebrate animals constituting the class Mammalia (), characterized by the presence of mammary glands which in females produce milk for feeding (nursing) their young, a neocortex (a region of the brain), fur ...

s. The larger sulci are usually called

fissure A fissure is a long, narrow crack opening along the surface of Earth. The term is derived from the Latin word , which means 'cleft' or 'crack'. Fissures emerge in Earth's crust, on ice sheets and glaciers, and on volcanoes. Ground fissure ...

Structure

Sulci, the grooves, and gyri, the folds or ridges, make up the folded surface of the

. Larger or deeper sulci are termed fissures, and in many cases the two terms are interchangeable. The folded cortex creates a larger surface area for the brain in humans and other mammals. When looking at the human brain, two-thirds of the surface are hidden in the grooves. The sulci and fissures are both grooves in the cortex, but they are differentiated by size. A sulcus is a shallower groove that surrounds a gyrus. A fissure is a large furrow that divides the brain into lobes and also into the two hemispheres as the longitudinal fissure.

Importance of expanded surface area

As the surface area of the brain increases more functions are made possible. A smooth-surfaced brain is only able to grow to a certain extent. A depression, sulcus, in the surface area allows for continued growth. This in turn allows for the functions of the brain to continue growing.

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 more prominent sulci are, however, seen across individuals – and even species – making a common nomenclature across individuals and species possible.

Development

In humans, cerebral convolutions appear at about 5 months and take at least into the first year after birth to fully develop. Development varies greatly between individuals. The potential influences of genetic,

epigenetic In biology, epigenetics is the study of stable phenotypic changes (known as ''marks'') that do not involve alterations in the DNA sequence. The Greek prefix '' epi-'' ( "over, outside of, around") in ''epigenetics'' implies features that are ...

and environmental factors are not fully understood. It has been found that the width of cortical sulci increases not only with age, but also with cognitive decline in the elderly.

Types

Sulci are divided into following categories: On the basis of function: #A limiting sulcus separates at its floor into two areas which are different functionally and structurally e.g. central sulcus between the motor and sensory areas. #Axial sulcus develops in the long axis of a rapidly growing homogeneous area e.g. postcalcarine sulcus in the long axis of the striate area. #Operculated sulcus separates by its lips into two areas and contains a third area in the walls of the sulcus e.g. lunate sulcus is an operculated sulcus, separating the striate and parastriate areas. On the basis of formation: #Primary sulci: formed before birth, independently. Example: central sulcus. #Secondary sulcus: produced by factors other than the exuberant growth in the adjoining areas of the cortex Examples are the lateral and parieto-occipital sulci. On the basis of depth: #Complete sulcus is very deep so as to cause elevation in the walls of the lateral ventricle. Examples are the collateral and calcarine sulci. #Incomplete sulci are superficially situated and are not very deep, E.g. paracentral sulcus.

Notable sulci

* Calcarine sulcus *

Central sulcus In neuroanatomy, the central sulcus (also central fissure, fissure of Rolando, or Rolandic fissure, after Luigi Rolando) is a sulcus, or groove, in the cerebral cortex in the brains of vertebrates. It is sometimes confused with the longitudinal ...

* Central sulcus of insula * Cingulate sulcus * Circular sulcus of insula * Callosal sulcus * Collateral sulcus * Fimbrodentate sulcus * Florance-robertal sulcus * Hippocampal sulcus * Inferior frontal sulcus *

Inferior temporal sulcus The inferior surface of the temporal lobe is concave, and is continuous posteriorly with the tentorial surface of the occipital lobe. It is traversed by the inferior temporal sulcus, which extends from near the occipital pole behind, to within a sh ...

Intraparietal sulcus The intraparietal sulcus (IPS) is located on the lateral surface of the parietal lobe, and consists of an oblique and a horizontal portion. The IPS contains a series of functionally distinct subregions that have been intensively investigated usi ...

* Lateral sulcus * Lunate sulcus * Occipitotemporal sulcus *

Olfactory sulcus The olfactory tract is a bilateral bundle of afferent nerve fibers from the mitral and tufted cells of the olfactory bulb that connects to several target regions in the brain, including the piriform cortex, amygdala, and entorhinal cortex. It ...

Paracentral sulcus The paracentral sulcus is a sulcus of the brain. It forms the paracentral lobule's anterior border. It is part of the cingulate sulcus. Gallery File:Gray727 cingulate sulcus.svg, Medial surface of left cerebral hemisphere. (Cingulate sulcus ...

* Parieto-occipital sulcus * Postcentral sulcus *

Precentral sulcus The precentral sulcus is a part of the human brain that lies parallel to, and in front of, the central sulcus. (A ''sulcus'' is one of the prominent grooves on the surface of the human brain.) The precentral sulcus divides the inferior, midd ...

Rhinal sulcus In the human brain, the entorhinal cortex appears as a longitudinal elevation anterior to the parahippocampal gyrus, with a corresponding internal furrow, the external rhinal sulcus (or rhinal fissure), separating it from the inferiolateral surface ...

* Subparietal sulcus *

Superior frontal sulcus The superior frontal sulcus is a sulcus between the superior frontal gyrus and the middle frontal gyrus. See also * Inferior frontal sulcus The inferior frontal sulcus is a sulcus between the middle frontal gyrus and the inferior frontal gyrus ...

* Superior temporal sulcus *

Transverse occipital sulcus The transverse occipital sulcus is a structure in the occipital lobe. The transverse occipital sulcus is continuous with the posterior end of the occipital ramus of the intraparietal sulcus The intraparietal sulcus (IPS) is located on the later ...

* Transverse temporal sulcus

Other animals

The variation in the number 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 gyrencephalics.Hofman MA. (1985). Size and shape of the cerebral cortex in mammals. I. The cortical surface. Brain Behav Evol. 27(1):28–40. Hofman MA. (1989).On the evolution and geometry of the brain in mammals. Prog Neurobiol.32(2):137–58. The division between the two groups occurs when cortical surface area is about 10 cm² and the brain has a volume of 3–4 cm³. Large rodents such as beavers () and capybaras () are gyrencephalic and smaller rodents such as rats and mice lissencephalic.

Macaque

macaque The macaques () constitute a genus (''Macaca'') of gregarious Old World monkeys of the subfamily Cercopithecinae. The 23 species of macaques inhabit ranges throughout Asia, North Africa, and (in one instance) Gibraltar. Macaques are principall ...

has a more simple sulcal pattern. In a monograph Bonin and Bailey list the following as the primary sulci:

Gerhardt von Bonin Gerhardt is a masculine name of Germanic origin. It can refer to the following: As a first name * Ants Eskola (1908–1989), Soviet-Estonian actor and singer born Gerhardt Esperk * Gerhardt Laves (1906–1993), American linguist * Gerhardt Neef ( ...

, Percival Bailey, ''The Neocortex of Macaca Mulatta'', The University of Illinois Press, Urbana, Illinois, 1947 * Calcarine fissure (ca) *

(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.

References

External links

Visual explanation of gyri, sulci, and fissures
{{DEFAULTSORT:Sulcus (Neuroanatomy) Neuroanatomy *