allocortex

{{short description|Type of cerebral cortex in the brain}}

{{Use dmy dates|date=February 2025}}

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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 in the brain, together with the neocortex. In the human brain, the allocortex is the much smaller area of cortex taking up just 10%; the neocortex takes up the remaining 90%.{{cite book |last1=Saladin |first1=K |title=Anatomy & physiology : the unity of form and function |date=2012 |publisher=McGraw-Hill |location=New York, NY |isbn=9780073378251 |pages=417 |edition=6th}} It is characterized by having just three cortical layers (one main neural layer), in contrast with the six cortical layers of the neocortex.{{cite journal |last1=Insausti |first1=R |last2=Muñoz-López |first2=M |last3=Insausti |first3=AM |last4=Artacho-Pérula |first4=E |title=The Human Periallocortex: Layer Pattern in Presubiculum, Parasubiculum and Entorhinal Cortex. A Review. |journal=Frontiers in Neuroanatomy |date=2017 |volume=11 |pages=84 |doi=10.3389/fnana.2017.00084 |doi-access=free |pmid=29046628|pmc=5632821 }} There are three subtypes of allocortex: the paleocortex, the archicortex, and the periallocortex—a transitional zone between the neocortex and the allocortex.{{Cite web |url=http://braininfo.rprc.washington.edu/centraldirectory.aspx?ID=2315 |title=periallocortex |institution=University of Washington |access-date=2024-12-14 |archive-url=https://web.archive.org/web/20240901131218/http://braininfo.rprc.washington.edu/centraldirectory.aspx?ID=2315 |archive-date=2024-09-01 |url-status=live}}

The specific regions of the brain usually described as belonging to the allocortex are the olfactory system and the hippocampus.

Allocortex is termed heterogenetic cortex, because during development it never has the six-layered architecture of homogenetic neocortex. It differs from 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 such as Brodmann area 4 that lacks granule cells.Crosby EC; Humphrey T; Lauer EW (1962). Correlative Anatomy of the Nervous System. New York: MacMillan.