Theallocortex(from Latin allo-, meaning other, and cortex, meaning bark or crust), orheterogenetic cortex,andneocortexare the two types ofcerebral cortexin thebrain.In thehuman brain,the allocortex is the much smaller area of cortex taking up just 10%; the neocortex takes up the remaining 90%.[1]It is characterized by having just three or four cortical layers, in contrast with the sixcortical layersof the neocortex. There are three subtypes of allocortex: thepaleocortex,thearchicortex,and theperiallocortex—a transitional zone between the neocortex and the allocortex.[2]
| Allocortex | |
|---|---|
| Identifiers | |
| NeuroNames | 1598 |
| NeuroLexID | nlx_143557 |
| TA98 | A14.1.09.305 |
| TA2 | 5529 |
| FMA | 83687 |
| Anatomical terms of neuroanatomy | |
The specific regions of the brain usually described as belonging to the allocortex are theolfactory systemand thehippocampus.
Allocortex is termed heterogenetic cortex, because during development it never has the six-layered architecture of homogenetic neocortex. It differs fromheterotypic cortex,a type of cerebral cortex, which during prenatal development, passes through a six-layered stage to have fewer layers, such as theagranular cortexsuch asBrodmann area 4that lacksgranule cells.[3]
Structure
editThe allocortex has three or four layers ofneuronal cell bodies,in contrast to the six layers of the neocortex. There are three subtypes of allocortex: the paleocortex, archicortex and periallocortex.[4]
Paleocortexis a type of thin, primitivecorticaltissue that consists of three cortical laminae (layers ofneuronal cell bodies).[5][6]The two granular layers II and IV of neocortex are absent in paleocortex. The main areas of paleocortex are theolfactory bulb,olfactory tubercleandpiriform cortex.
Archicortexis a type of cortical tissue that consists of fourlaminae(layers ofneuronal cell bodies).[7]The main areas of archicortex are thehippocampusanddentate gyrus.
Periallocortexis a transitional form between neocortex and either paleo- or archicortex. It thus can be either peripaleocortex (anterior insular cortex) orperiarchicortex(entorhinal cortex,presubicular cortex,retrosplenial,supracallosal,andsubgenualareas).
Because the number of laminae that compose a type of cortical tissue seems to be directly proportional[citation needed]to both the information-processing capabilities of that tissue and itsphylogenetic age,and also because olfaction is a major sensory modality in phylogenetically early animals, paleocortex is thought to be the most primitive form of cortex.[6]
See also
editReferences
edit- ^Saladin, K (2012).Anatomy & physiology: the unity of form and function(6th ed.). New York, NY: McGraw-Hill. p. 417.ISBN9780073378251.
- ^"BrainInfo".
- ^Crosby EC; Humphrey T; Lauer EW (1962)Correlative Anatomy of the Nervous System. New York: MacMillan
- ^Filimonoff, IN (1947). "A rational subdivision of the cerebral cortex".Arch Neurol Psychiatry.58(3): 296–311.doi:10.1001/archneurpsyc.1947.02300320047002.PMID20265596.
- ^"Paleocortex".BrainInfo.University of Washington.Retrieved5 May2013.
- ^abPurves, Dale; Augustine, George J; Fitzpatrick, David; Hall, William C; LaMantia, Anthony-Samuel; White, Leonard E (2011).Neuroscience(5th ed.). Sinauer Associates Inc. p. 666.ISBN9780878936465.
- ^"Archicortex".BrainInfo.University of Washington.Retrieved17 March2017.
- "Allocortex."Stedman's Medical Dictionary, 27th ed.(2000).ISBN0-683-40007-X
- Haines, Duane E.Fundamental Neuroscience, 2nd.(2002).ISBN0-443-06603-5