Corpus callosum
Corpus callosum | |
---|---|
Details | |
Pronunciation | /ˈkɔːrpəs kəˈloʊsəm/ |
Part of | Human brain |
Parts | Genu, rostrum, trunk, splenium |
Identifiers | |
MeSH | D003337 |
NeuroNames | 191 |
NeuroLex ID | birnlex_1087 |
TA98 | A14.1.09.241 |
TA2 | 5604 |
FMA | 86464 |
Anatomical terms of neuroanatomy |
The corpus callosum (Latin for "tough body"), also callosal commissure, is a wide, thick nerve tract, consisting of a flat bundle of commissural fibers, beneath the cerebral cortex in the brain. The corpus callosum is only found in placental mammals.[1] It spans part of the longitudinal fissure, connecting the left and right cerebral hemispheres, enabling communication between them. It is the largest white matter structure in the human brain, about 10 in (250 mm) in length and consisting of 200–300 million axonal projections.[2][3]
A number of separate nerve tracts, classed as subregions of the corpus callosum, connect different parts of the hemispheres. The main ones are known as the genu, the rostrum, the trunk or body, and the splenium.[4]
Structure
The corpus callosum forms the floor of the
The corpus callosum has four main parts – individual nerve tracts that connect different parts of the hemispheres. These are the rostrum, the genu, the trunk or body, and the splenium.[4] A narrowed part between the trunk and the splenium is known as the isthmus. Fibres from the trunk and the splenium known together as the tapetum form the roof of each lateral ventricle.[6]
The front part of the corpus callosum, towards the frontal lobes, is called the genu ("knee"). The genu curves downward and backward in front of the septum pellucidum, diminishing greatly in thickness. The lower, much thinner part is the rostrum and is connected below with the lamina terminalis, which stretches from the interventricular foramina to the recess at the base of the optic stalk. The rostrum is named for its resemblance to a bird's beak.
The end part of the corpus callosum, towards the cerebellum, is called the splenium. This is the thickest part, and overlaps the tela choroidea of the third ventricle and the midbrain, and ends in a thick, convex, free border. Splenium translates as "bandage" in Greek.
The trunk of the corpus callosum lies between the splenium and the genu.
The callosal sulcus is a
Relations
On either side of the corpus callosum, the fibers radiate in the
The anterior cerebral arteries are in contact with the undersurface of the rostrum; they arch over the front of the genu and are carried along the trunk, supplying the front four-fifths of the corpus callosum.[7]
Neuronal fibers
The size, amount of myelination, and density of the fibers in the subregions relate to the functions of the brain regions they connect.[8] Myelination is the process of coating neurons with myelin, which helps the transfer of information between neurons. The process is believed to occur until an individual's thirties with peak growth in the first decade of one's life.[9] Thinner, lightly myelinated fibers are slower conducting and they connect the association and prefrontal areas. Thicker and fast-conducting fibers connect the visual and motor areas.[10]
The
Thinner
A study of five- to eighteen-year-olds found a positive correlation between age and callosal thickness.[3]
Variation between sexes
The corpus callosum and its
Using
Analysis by shape and size has also been used to study specific three-dimensional mathematical relationships with MRIs, and have found consistent and statistically significant differences between sexes.[19][20] Specific algorithms have found significant differences between the two sexes in over 70% of cases in one review.[21]
A 2005 study on the sizes and structures of the corpus callosum in transgender people found it to be structurally more in line with their declared gender than their assigned sex. [21]
Correlates of size with handedness
One study reported that the front portion of the human corpus callosum was 0.75 cm2 or 11% larger in
Clinical significance
Epilepsy
The symptoms of refractory (difficult to treat)
Failure to develop
The formation of the corpus callosum begins with the first midline crossing of pioneer axons around week 12 in the
ACC is usually not fatal. Treatment usually involves management of symptoms, such as hydrocephaly and seizures, if they occur. Although many children with the disorder lead normal lives and have average intelligence, careful neuropsychological testing reveals subtle differences in higher cortical function compared to individuals of the same age and education without ACC. Children with ACC accompanied by developmental delay and/or seizure disorders should be screened for metabolic disorders.[31]
In addition to agenesis of the corpus callosum, similar conditions are hypogenesis (partial formation), dysgenesis (malformation), and hypoplasia (underdevelopment, including too thin).
Other studies have also linked possible correlations between corpus callosum malformation and autism spectrum disorders.[32][33]
Kim Peek, a savant and the inspiration behind the movie Rain Man, was found with agenesis of the corpus callosum, as part of FG syndrome.
Other disease
Anterior corpus callosum lesions may result in akinetic mutism or anomic aphasia. See also:
- Alien hand syndrome
- Dyslexia without agraphia (seen with damage to splenium of corpus callosum)
- Marchiafava–Bignami disease a degenerative disease characterised by loss of myelin and necrosis of the corpus callosum
- Multiple sclerosis with the Dawson's fingers sign
- Reversible splenial lesion syndrome – a rare encephalopathy of unknown origin with a transient lesion in the splenium, mostly associated with infectious diseases
- Septo-optic dysplasia (de Morsier syndrome)
- Split-brain
- Susac's syndrome characterised by lesions as small holes in the corpus callosum
History
The first study of the corpus with relation to gender was by R. B. Bean, a Philadelphia anatomist, who suggested in 1906 that "exceptional size of the corpus callosum may mean exceptional intellectual activity" and that there were measurable differences between men and women. Perhaps reflecting the political climate of the times, he went on to claim differences in the size of the callosum across different races. His research was ultimately refuted by Franklin Mall, the director of his own laboratory.[34]
Of more mainstream impact was a 1982 Science article by Holloway and Utamsing that suggested sex difference in human brain morphology, which related to differences in cognitive ability.[35] Time published an article in 1992 that suggested that, because the corpus is "often wider in the brains of women than in those of men, it may allow for greater cross-talk between the hemispheres—possibly the basis for women’s intuition."[36]
Later publications in the psychology literature have raised doubt as to whether the anatomic size of the corpus is actually different. A meta-analysis of 49 studies since 1980 found that, contrary to de Lacoste-Utamsing and Holloway, no sex difference could be found in the size of the corpus callosum, whether or not any account was taken of larger male brain size.[34] A study in 2006 using thin slice MRI showed no difference in thickness of the corpus when accounting for the size of the subject.[37]
Other animals
The corpus callosum is found only in
Additional images
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Corpus callosum
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Coronal T2 (grey scale inverted) MRI of the brain at the level of the caudate nuclei emphasizing corpus callosum
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Tractography of Corpus callosum
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Corpus callosum with Anatomography
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Sagittal post mortem section through the midline brain. The corpus callosum is the curved band of lighter tissue at the center of the brain above the hypothalamus. Its lighter texture is due to higher myelincontent, resulting in faster neuronal impulse transmission.
References
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- ^ "Corpus callosum". Queensland Brain Institute. 10 November 2017.
- ^ PMID 20720105.
- ^ a b c Gaillard, Frank. "Corpus callosum | Radiology Reference Article | Radiopaedia.org". radiopaedia.org.
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- ^ "NIAAA Publications". pubs.niaaa.nih.gov. Archived from the original on 2021-11-07. Retrieved 2018-09-17.
- ^ PMID 19875694.
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- ^ S2CID 351426.
- ^ PMID 4023705.
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- ^ "WebMd Corpus Callotomy". Web MD. July 18, 2010. Archived from the original on July 2, 2010. Retrieved July 18, 2010.
- S2CID 40226538.
- S2CID 29992703.
- PMID 8554070.
- ^ "NINDS Agenesis of the Corpus Callosum Information Page: NINDS". RightDiagnosis.com. Archived from the original on 2012-03-24. Retrieved Aug 30, 2011.
- PMID 30567587.
- ^ "Autism May Involve A Lack Of Connections And Coordination In Separate Areas Of The Brain, Researchers Find". Medical News Today. Archived from the original on 2011-10-15.
- ^ S2CID 9909395.
- PMID 7089533.
- ^ C Gorman (20 January 1992). "Sizing up the sexes". Time. pp. 36–43. As cited by Bishop and Wahlsten.
- S2CID 14466914.
- PMID 16587795.
- ^ Sarnat, Harvey B., and Paolo Curatolo (2007). Malformations of the Nervous System: Handbook of Clinical Neurology, p. 68[permanent dead link]
- ^ Ashwell, Ken (2010). The Neurobiology of Australian Marsupials: Brain Evolution in the Other Mammalian Radiation, p. 50
- ^ Armati, Patricia J., Chris R. Dickman, and Ian D. Hume (2006). Marsupials, p. 175
- ^ Butler, Ann B., and William Hodos (2005). Comparative Vertebrate Neuroanatomy: Evolution and Adaptation, p. 361
- ^ Morris, H., & Schaeffer, J. P. (1953). The Nervous system-The Brain or Encephalon. Human anatomy; a complete systematic treatise. (11th ed., pp. 920–921, 964–965). New York: Blakiston.
External links
- Stained brain slice images which include the "corpus callosum" at the BrainMaps project
- Comparative Neuroscience at Wikiversity
- NIF Search – Corpus callosum Archived 2016-03-04 at the Wayback Machine via the Neuroscience Information Framework
- National Organization for Disorders of the Corpus Callosum
- A 3D model of corpus callosum