Gyrus

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Gyrus
Gyrus sulcus-en.svg
Gyrus and sulcus
Identifiers
TA98 A14.1.09.004
TA2 5432
FMA 83874
Anatomical terminology
Gray's FIG. 726 - Lateral surface of left cerebral hemisphere, viewed from the side Gray726.png
Gray's FIG. 726 – Lateral surface of left cerebral hemisphere, viewed from the side
Gray's Fig. 727 - Medial surface of left cerebral hemisphere Gray727.svg
Gray's Fig. 727 – Medial surface of left cerebral hemisphere

In neuroanatomy, a gyrus (pl.: gyri) is a ridge on the cerebral cortex. It is generally surrounded by one or more sulci (depressions or furrows; sg.: sulcus). [1] Gyri and sulci create the folded appearance of the brain in humans and other mammals.

Contents

Structure

The gyri are part of a system of folds and ridges that create a larger surface area for the human brain and other mammalian brains. [2] Because the brain is confined to the skull, brain size is limited. Ridges and depressions create folds allowing a larger cortical surface area, and greater cognitive function, to exist in the confines of a smaller cranium. [3]

Development

The human brain undergoes gyrification during fetal and neonatal development. In embryonic development, all mammalian brains begin as smooth structures derived from the neural tube. A cerebral cortex without surface convolutions is lissencephalic, meaning 'smooth-brained'. [4] As development continues, gyri and sulci begin to take shape on the fetal brain, with deepening indentations and ridges developing on the surface of the cortex. [5]

Clinical significance

Changes in the structure of gyri in the cerebral cortex are associated with various diseases and disorders. Pachygyria, lissencephaly, and polymicrogyria are all the results of abnormal cell migration associated with a disorganized cellular architecture, failure to form six layers of cortical neurons (a four-layer cortex is common), and functional problems. [6] The abnormal formation is commonly associated with epilepsy and mental dysfunctions. [7]

Pachygyria (meaning "thick" or "fat" gyri) is a congenital malformation of the cerebral hemisphere, resulting in unusually thick gyri in the cerebral cortex. [8] Pachygyria is used to describe brain characteristics in association with several neuronal migration disorders; most commonly relating to lissencephaly.

Lissencephaly (smooth brain) is a rare congenital brain malformation caused by defective neuronal migration during the 12th to 24th weeks of fetal gestation resulting in a lack of development of gyri and sulci. [9]

Polymicrogyria (meaning "many small gyri") is a developmental malformation of the human brain characterized by excessive folding of the gyri and a thickening of the cerebral cortex. [10] It may be generalized, affecting the whole surface of the cerebral cortex or may be focal, affecting only parts of the surface. Polymicrogyria may be caused by mutations within several genes, including ion channels. [11]

Notable gyri

See also

Related Research Articles

<span class="mw-page-title-main">Cerebral cortex</span> Outer layer of the cerebrum of the mammalian brain

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. It is the largest site of neural integration in the central nervous system. and plays a key role in attention, perception, awareness, thought, memory, language, and consciousness. The cerebral cortex is the part of the brain responsible for cognition.

<span class="mw-page-title-main">Lissencephaly</span> Medical condition

Lissencephaly is a set of rare brain disorders whereby the whole or parts of the surface of the brain appear smooth. It is caused by defective neuronal migration during the 12th to 24th weeks of gestation resulting in a lack of development of brain folds (gyri) and grooves (sulci). It is a form of cephalic disorder. Terms such as agyria and pachygyria are used to describe the appearance of the surface of the brain.

<span class="mw-page-title-main">Brodmann area</span> Region of the brain

A Brodmann area is a region of the cerebral cortex, in the human or other primate brain, defined by its cytoarchitecture, or histological structure and organization of cells. The concept was first introduced by the German anatomist Korbinian Brodmann in the early 20th century. Brodmann mapped the human brain based on the varied cellular structure across the cortex and identified 52 distinct regions, which he numbered 1 to 52. These regions, or Brodmann areas, correspond with diverse functions including sensation, motor control, and cognition.

<span class="mw-page-title-main">Frontal lobe</span> Part of the brain

The frontal lobe is the largest of the four major lobes of the brain in mammals, and is located at the front of each cerebral hemisphere. It is parted from the parietal lobe by a groove between tissues called the central sulcus and from the temporal lobe by a deeper groove called the lateral sulcus. The most anterior rounded part of the frontal lobe is known as the frontal pole, one of the three poles of the cerebrum.

<span class="mw-page-title-main">Neocortex</span> Mammalian structure involved in higher-order brain functions

The neocortex, also called the neopallium, isocortex, or the six-layered cortex, is a set of layers of the mammalian cerebral cortex involved in higher-order brain functions such as sensory perception, cognition, generation of motor commands, spatial reasoning and language. The neocortex is further subdivided into the true isocortex and the proisocortex.

<span class="mw-page-title-main">Brodmann area 11</span> Brain area

Brodmann area 11 is one of Brodmann's cytologically defined regions of the brain. It is in the orbitofrontal cortex which is above the eye sockets (orbitae). It is involved in decision making, processing rewards, and encoding new information into long-term memory.

<span class="mw-page-title-main">Fusiform gyrus</span> Gyrus of the temporal and occipital lobes of the brain

The fusiform gyrus, also known as the lateral occipitotemporal gyrus,is part of the temporal lobe and occipital lobe in Brodmann area 37. The fusiform gyrus is located between the lingual gyrus and parahippocampal gyrus above, and the inferior temporal gyrus below. Though the functionality of the fusiform gyrus is not fully understood, it has been linked with various neural pathways related to recognition. Additionally, it has been linked to various neurological phenomena such as synesthesia, dyslexia, and prosopagnosia.

<span class="mw-page-title-main">Polymicrogyria</span> Medical condition

Polymicrogyria (PMG) is a condition that affects the development of the human brain by multiple small gyri (microgyri) creating excessive folding of the brain leading to an abnormally thick cortex. This abnormality can affect either one region of the brain or multiple regions.

<span class="mw-page-title-main">Inferior frontal gyrus</span> Part of the brains prefrontal cortex

The inferior frontal gyrus (IFG),, is the lowest positioned gyrus of the frontal gyri, of the frontal lobe, and is part of the prefrontal cortex.

Bilateral frontoparietal polymicrogyria is a genetic disorder with autosomal recessive inheritance that causes a cortical malformation. Our brain has folds in the cortex to increase surface area called gyri and patients with polymicrogyria have an increase number of folds and smaller folds than usual. Polymicrogyria is defined as a cerebral malformation of cortical development in which the normal gyral pattern of the surface of the brain is replaced by an excessive number of small, fused gyri separated by shallow sulci and abnormal cortical lamination. From ongoing research, mutation in GPR56, a member of the adhesion G protein-coupled receptor (GPCR) family, results in BFPP. These mutations are located in different regions of the protein without any evidence of a relationship between the position of the mutation and phenotypic severity. It is also found that GPR56 plays a role in cortical pattering.

<span class="mw-page-title-main">Middle cerebral artery</span> Paired artery that supplies blood to the cerebrum

The middle cerebral artery (MCA) is one of the three major paired cerebral arteries that supply blood to the cerebrum. The MCA arises from the internal carotid artery and continues into the lateral sulcus where it then branches and projects to many parts of the lateral cerebral cortex. It also supplies blood to the anterior temporal lobes and the insular cortices.

<span class="mw-page-title-main">Lobes of the brain</span> Parts of the cerebrum

The lobes of the brain are the major identifiable zones of the human cerebral cortex, and they comprise the surface of each hemisphere of the cerebrum. The two hemispheres are roughly symmetrical in structure, and are connected by the corpus callosum. They traditionally have been divided into four lobes, but are today considered as having six lobes each. The lobes are large areas that are anatomically distinguishable, and are also functionally distinct to some degree. Each lobe of the brain has numerous ridges, or gyri, and furrows, the sulci that constitute further subzones of the cortex. The expression "lobes of the brain" usually refers only to those of the cerebrum, not to the distinct areas of the cerebellum.

<span class="mw-page-title-main">Posterior cerebral artery</span> Artery which supplies blood to the occipital lobe of the brain

The posterior cerebral artery (PCA) is one of a pair of cerebral arteries that supply oxygenated blood to the occipital lobe, part of the back of the human brain. The two arteries originate from the distal end of the basilar artery, where it bifurcates into the left and right posterior cerebral arteries. These anastomose with the middle cerebral arteries and internal carotid arteries via the posterior communicating arteries.

Pachygyria is a congenital malformation of the cerebral hemisphere. It results in unusually thick convolutions of the cerebral cortex. Typically, children have developmental delay and seizures, the onset and severity depending on the severity of the cortical malformation. Infantile spasms are common in affected children, as is intractable epilepsy.

<span class="mw-page-title-main">Middle temporal gyrus</span> One of three gyri of the temporal lobe of the brain

Middle temporal gyrus is a gyrus in the brain on the temporal lobe. It is located between the superior temporal gyrus and inferior temporal gyrus. It corresponds largely to Brodmann area 21.

<span class="mw-page-title-main">Inferior temporal gyrus</span> One of three gyri of the temporal lobe of the brain

The inferior temporal gyrus is one of three gyri of the temporal lobe and is located below the middle temporal gyrus, connected behind with the inferior occipital gyrus; it also extends around the infero-lateral border on to the inferior surface of the temporal lobe, where it is limited by the inferior sulcus. This region is one of the higher levels of the ventral stream of visual processing, associated with the representation of objects, places, faces, and colors. It may also be involved in face perception, and in the recognition of numbers and words.

<span class="mw-page-title-main">Sulcus (neuroanatomy)</span> Fold in the surface of the brain

In neuroanatomy, a sulcus is a depression or groove in the cerebral cortex. It surrounds a gyrus, creating the characteristic folded appearance of the brain in humans and other mammals. The larger sulci are usually called fissures.

Gyrification is the process of forming the characteristic folds of the cerebral cortex.

<span class="mw-page-title-main">Microlissencephaly</span> Microcephaly combined with lissencephaly

Microlissencephaly (MLIS) is a rare congenital brain disorder that combines severe microcephaly with lissencephaly. Microlissencephaly is a heterogeneous disorder, i.e. it has many different causes and a variable clinical course. Microlissencephaly is a malformation of cortical development (MCD) that occurs due to failure of neuronal migration between the third and fifth month of gestation as well as stem cell population abnormalities. Numerous genes have been found to be associated with microlissencephaly, however, the pathophysiology is still not completely understood.

<span class="mw-page-title-main">Occipital gyri</span> Three parallel gyri of the occipital lobe of the brain

The occipital gyri (OcG) are three gyri in parallel, along the lateral portion of the occipital lobe, also referred to as a composite structure in the brain. The gyri are the superior occipital gyrus, the middle occipital gyrus, and the inferior occipital gyrus, and these are also known as the occipital face area. The superior and inferior occipital sulci separates the three occipital gyri.

References

  1. Deng, Fan; Jiang, Xi; Zhu, Dajiang; Zhang, Tuo; Li, Kaiming; Guo, Lei; Liu, Tianming (2013). "A functional model of cortical gyri and sulci". Brain Structure and Function. 219 (4): 1473–1491. doi:10.1007/s00429-013-0581-z. ISSN   1863-2653. PMC   3909019 . PMID   23689502.
  2. Marieb, Elaine N.; Hoehn, Katja (2012). Human Anatomy & Physiology (9th ed.). Pearson. ISBN   978-0321852120.
  3. Cusack, Rhodri (April 2005). "The Intraparietal Sulcus and Perceptual Organization". Journal of Cognitive Neuroscience. 17 (4): 641–651. CiteSeerX   10.1.1.452.462 . doi:10.1162/0898929053467541. PMID   15829084. S2CID   25453338.
  4. Armstrong, E; Schleicher, A; Omran, H; Curtis, M; Zilles, K (1991). "The ontogeny of human gyrification". Cerebral Cortex. 5 (1): 56–63. doi:10.1093/cercor/5.1.56. PMID   7719130.
  5. Rajagopalan, V; Scott, J; Habas, PA; Kim, K; Corbett-Detig, J; Rousseau, F; Barkovich, AJ; Glenn, OA; Studholme, C (23 February 2011). "Local tissue growth patterns underlying normal fetal human brain gyrification quantified in utero". The Journal of Neuroscience. 31 (8): 2878–87. doi:10.1523/jneurosci.5458-10.2011. PMC   3093305 . PMID   21414909.
  6. Barkovich, A. J.; Guerrini, R.; Kuzniecky, R. I.; Jackson, G. D.; Dobyns, W. B. (2012). "A developmental and genetic classification for malformations of cortical development: update 2012". Brain. 135 (5): 1348–1369. doi:10.1093/brain/aws019. ISSN   0006-8950. PMC   3338922 . PMID   22427329.
  7. Pang, Trudy; Atefy, Ramin; Sheen, Volney (2008). "Malformations of Cortical Development". The Neurologist. 14 (3): 181–191. doi:10.1097/NRL.0b013e31816606b9. ISSN   1074-7931. PMC   3547618 . PMID   18469675.
  8. Guerrini R (2005). "Genetic malformations of the cerebral cortex and epilepsy". Epilepsia. 46 (Suppl 1): 32–37. doi: 10.1111/j.0013-9580.2005.461010.x . PMID   15816977. S2CID   24119081.
  9. Dobyns WB (1987). "Developmental aspects of lissencephaly and the lissencephaly syndromes". Birth Defects Orig. Artic. Ser. 23 (1): 225–41. PMID   3472611.
  10. Chang, B; Walsh, CA; Apse, K; Bodell, A; Pagon, RA; Adam, TD; Bird, CR; Dolan, K; Fong, MP; Stephens, K (1993). "Polymicrogyria Overview". GeneReviews. PMID   20301504.
  11. Smith, RS; Walsh, CA (February 2020). "Ion Channel Functions in Early Brain Development". Trends in Neurosciences. 43 (2): 103–114. doi:10.1016/j.tins.2019.12.004. PMC   7092371 . PMID   31959360.