# Allocortex

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Type of cerebral cortex in the brain

Allocortex Identifiers NeuroNames 1598 NeuroLex ID nlx_143557 TA98 A14.1.09.305 TA2 5529 FMA 83687 Anatomical terms of neuroanatomy [edit on Wikidata]

The **allocortex** (from Latin allo-, meaning other, and cortex, meaning bark or crust), or **heterogenetic cortex**, is one of the two types of [cerebral cortex](/source/Cerebral_cortex) in the [brain](/source/Brain), together with the [neocortex](/source/Neocortex). In the [human brain](/source/Human_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 cortical layers (one main neural layer), in contrast with the six [cortical layers](/source/Cortical_layers) of the neocortex.[2] There are three subtypes of allocortex: the [paleocortex](/source/Paleocortex), the [archicortex](/source/Archicortex), and the [periallocortex](/source/Periallocortex)—a transitional zone between the neocortex and the allocortex.[3]

The specific regions of the brain usually described as belonging to the allocortex are the [olfactory system](/source/Olfactory_system) and the [hippocampus](/source/Hippocampus).

Allocortex is termed heterogenetic cortex, because during development it never has the six-layered architecture of homogenetic neocortex. It differs from [heterotypic cortex](/source/Heterotypic_cortex), a type of cerebral cortex, which during prenatal development, passes through a six-layered stage to have fewer layers, such as the [agranular cortex](/source/Agranular_cortex) such as [Brodmann area 4](/source/Brodmann_area_4) that lacks [granule cells](/source/Granule_cell).[4]

## Structure

The allocortex has three layers (one main neuronal layer) in contrast to the six layers of the neocortex.[2] There are three subtypes of allocortex: the paleocortex, archicortex and periallocortex.[5]

[Paleocortex](/source/Paleocortex) is a type of thin, primitive [cortical](/source/Cerebral_cortex) tissue that consists of three cortical laminae (layers of [neuronal cell bodies](/source/Perikaryon)).[6][7] The two granular layers II and IV of neocortex are absent in paleocortex. The main areas of paleocortex are the [olfactory bulb](/source/Olfactory_bulb), [olfactory tubercle](/source/Olfactory_tubercle) and [piriform cortex](/source/Piriform_cortex).

[Archicortex](/source/Archicortex) is a type of cortical tissue that consists of four [laminae](/source/Cerebral_cortex#Layered_structure) (layers of [neuronal cell bodies](/source/Perikaryon)).[8] The main areas of archicortex are the [hippocampus](/source/Hippocampus) and [dentate gyrus](/source/Dentate_gyrus).

[Periallocortex](/source/Periallocortex) is a transitional form between neocortex and either paleo- or archicortex. It thus can be either peripaleocortex (anterior insular cortex) or [periarchicortex](/source/Periarchicortex) ([entorhinal cortex](/source/Entorhinal_cortex), presubicular cortex, [retrosplenial](/source/Retrosplenial_cortex), [supracallosal](/source/Indusium_griseum), and [subgenual](/source/Brodmann_area_25) areas).

Because the number of laminae that compose a type of cortical tissue seems to be directly proportional [*[citation needed](https://en.wikipedia.org/wiki/Wikipedia:Citation_needed)*] to both the information-processing capabilities of that tissue and its [phylogenetic age](/source/Phylogenetics), and also because olfaction is a major sensory modality in phylogenetically early animals, paleocortex is thought to be the most primitive form of cortex.[7]

## See also

- [Paralimbic cortex](/source/Paralimbic_cortex)

## References

1. **[^](#cite_ref-Saladin_1-0)** Saladin, K (2012). *Anatomy & physiology : the unity of form and function* (6th ed.). New York, NY: McGraw-Hill. p. 417. [ISBN](/source/ISBN_(identifier)) [9780073378251](https://en.wikipedia.org/wiki/Special:BookSources/9780073378251).

1. ^ [***a***](#cite_ref-Insausti2017_2-0) [***b***](#cite_ref-Insausti2017_2-1) Insausti, R; Muñoz-López, M; Insausti, AM; Artacho-Pérula, E (2017). ["The Human Periallocortex: Layer Pattern in Presubiculum, Parasubiculum and Entorhinal Cortex. A Review"](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5632821). *Frontiers in Neuroanatomy*. **11**: 84. [doi](/source/Doi_(identifier)):[10.3389/fnana.2017.00084](https://doi.org/10.3389%2Ffnana.2017.00084). [PMC](/source/PMC_(identifier)) [5632821](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5632821). [PMID](/source/PMID_(identifier)) [29046628](https://pubmed.ncbi.nlm.nih.gov/29046628).

1. **[^](#cite_ref-3)** ["periallocortex"](http://braininfo.rprc.washington.edu/centraldirectory.aspx?ID=2315). University of Washington. [Archived](https://web.archive.org/web/20240901131218/http://braininfo.rprc.washington.edu/centraldirectory.aspx?ID=2315) from the original on 1 September 2024. Retrieved 14 December 2024.

1. **[^](#cite_ref-4)** Crosby EC; Humphrey T; Lauer EW (1962). *Correlative Anatomy of the Nervous System*. New York: MacMillan.

1. **[^](#cite_ref-5)** Filimonoff, IN (1947). "A rational subdivision of the cerebral cortex". *Arch Neurol Psychiatry*. **58** (3): 296–311. [doi](/source/Doi_(identifier)):[10.1001/archneurpsyc.1947.02300320047002](https://doi.org/10.1001%2Farchneurpsyc.1947.02300320047002). [PMID](/source/PMID_(identifier)) [20265596](https://pubmed.ncbi.nlm.nih.gov/20265596).

1. **[^](#cite_ref-BrainInfo_Paleocortex_6-0)** ["Paleocortex"](http://braininfo.rprc.washington.edu/centraldirectory.aspx?type=a&ID=2336). *BrainInfo*. University of Washington. Retrieved 5 May 2013.

1. ^ [***a***](#cite_ref-Purves_2011_7-0) [***b***](#cite_ref-Purves_2011_7-1) Purves, Dale; Augustine, George J; Fitzpatrick, David; Hall, William C; LaMantia, Anthony-Samuel; White, Leonard E (2011). *Neuroscience* (5th ed.). Sinauer Associates Inc. p. 666. [ISBN](/source/ISBN_(identifier)) [9780878936465](https://en.wikipedia.org/wiki/Special:BookSources/9780878936465).

1. **[^](#cite_ref-BrainInfo_Archicortex_8-0)** ["Archicortex"](http://braininfo.rprc.washington.edu/CentralDirectory.aspx?ID=170). *BrainInfo*. University of Washington. Retrieved 17 March 2017.

- "Allocortex." *Stedman's Medical Dictionary, 27th ed.* (2000). [ISBN](/source/ISBN_(identifier)) [0-683-40007-X](https://en.wikipedia.org/wiki/Special:BookSources/0-683-40007-X)

- Haines, Duane E. *Fundamental Neuroscience, 2nd.* (2002). [ISBN](/source/ISBN_(identifier)) [0-443-06603-5](https://en.wikipedia.org/wiki/Special:BookSources/0-443-06603-5)

v t e Types of cerebral cortex Structure types Isocortex True isocortex or Neocortex Proisocortex Allocortex Paleocortex Archicortex Line of Gennari Layers Internal granular layer External granular layer Cells Betz cell Pyramidal cell Stellate cell

Authority control databases Terminologia Anatomica

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