# Archicortex
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> Source: https://en.wikipedia.org/wiki/Archicortex
> Source revision: 1296106576
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{{short description|Phylogenetically oldest part of the cerebral cortex or pallium}}
{{Infobox Brain
| Name = Archicortex
| Latin = archicortex
| Image = CajalHippocampus (modified).png
| Caption = The archicortex in humans is a synonym of the [hippocampal formation](/source/hippocampal_formation). The hippocampal formation is shown here, as drawn by [Santiago Ramon y Cajal](/source/Santiago_Ramon_y_Cajal): DG: dentate gyrus. Sub: subiculum. EC: entorhinal cortex. CA1-CA3: hippocampus proper
| Image2 =
| Caption2 =
| IsPartOf = [cerebral cortex](/source/cerebral_cortex) or [pallium](/source/Pallium_(neuroanatomy))
| System = [Olfactory system](/source/Olfactory_system)
}}
The '''archicortex''', or '''archipallium''', is the [phylogenetically](/source/Phylogenetics) second oldest region of the [brain](/source/brain)'s [cerebral cortex](/source/cerebral_cortex) (the oldest is the [paleocortex](/source/paleocortex)). In older species, such as fish, the archipallium makes up most of the [cerebrum](/source/telencephalon). [Amphibian](/source/Amphibian)s develop an archipallium and [paleopallium](/source/paleopallium).
In humans, the archicortex makes up the three [cortical layer](/source/cortical_layer)s of the [hippocampus](/source/hippocampus).[{{cite book |last1=Purves |first1=Dale |title=Neuroscience |date=2012 |location=Sunderland, Mass. |isbn=9780878936953 |page=731 |edition=5th}}] It has fewer [cortical layer](/source/cortical_layer)s than both the [neocortex](/source/neocortex), which has six, and the [paleocortex](/source/paleocortex), which has either four or five. The archicortex, along with the paleocortex and [periallocortex](/source/periallocortex), is a subtype of [allocortex](/source/allocortex).[{{cite web|title=Paleocortex|url=http://braininfo.rprc.washington.edu/centraldirectory.aspx?type=a&ID=2336|work=BrainInfo|publisher=University of Washington|access-date=5 May 2013}}] Because the number of cortical layers that make up a type of cortical tissue seems to be directly proportional{{clarify|date=February 2024}} to both the information-processing capabilities of that tissue and its [phylogenetic age](/source/phylogenetics), the archicortex is thought to be the oldest and most basic type of cortical tissue.[{{cite book|author=Purves, Dale|author2=Augustine, George J|author3=Fitzpatrick, David|author4=Hall, William C|author5=LaMantia, Anthony-Samuel|author6=White, Leonard E|title=Neuroscience|year=2011|publisher=Sinauer Associates Inc.|isbn=9780878936465|edition=5th}}]
==Location==
The archicortex is most prevalent in the [olfactory cortex](/source/primary_olfactory_cortex) and the [hippocampus](/source/hippocampus),[{{cite journal|last1=Wills|first1=Tom J.|last2=Cacucci|first2=Francesca |last3=Burgess|first3=Neil|last4=O'Keefe|first4=John|title=Development of the Hippocampal Cognitive Map in Preweanling Rats|journal=Science|date=18 June 2010|volume=328|issue=5985 |pages=1573–1576|doi=10.1126/science.1188224|pmid=20558720|pmc=3543985|bibcode=2010Sci...328.1573W}}] which are responsible for processing smells and forming memories, respectively.[{{cite book|last=Haberly|first=Lewis B|title=Cerebral Cortex|year=1990|isbn=978-1-4615-3824-0 |pages=137–166|edition=8B|chapter=Comparative Aspects of Olfactory Cortex|publisher=Springer }}] Because olfaction is considered to be the phylogenetically oldest sensory modality,[{{cite journal|last1=Albrecht|first1=J.|last2=Wiesmann|first2=M.|title=Das olfaktorische System des Menschen|journal=Der Nervenarzt|date=August 2006|volume=77|issue=8 |pages=931–939|doi=10.1007/s00115-006-2121-z|pmid=16871378}}] and the [limbic system](/source/limbic_system), of which the hippocampus is a part, is one of the oldest systems in the brain,[{{cite journal |last1=Rajmohan|first1=V.|last2=Mohandas|first2=E.|title=The limbic system|journal=Indian Journal of Psychiatry|date=April–June 2007|volume=49|issue=2|pages=132–139 |doi=10.4103/0019-5545.33264|pmid=20711399|pmc=2917081 |doi-access=free }}] it is likely that the archicortex was one of the first types of tissue to develop in primitive [nervous system](/source/nervous_system)s.[{{cite journal|last1=Pellegrini|first1=M.|last2=Mansouri |first2=A.|last3=Simeone|first3=A.|last4=Boncinelli|first4=E.|last5=Gruss|first5=P.|title=Dentate gyrus formation requires Emx2|journal=Development|date=December 1996|volume=122|issue=12 |pages=3893–3898|doi=10.1242/dev.122.12.3893|pmid=9012509|hdl=11858/00-001M-0000-0013-00C2-8|hdl-access=free}}]
== Structure ==
The archicortex is largely made up of memorizing cells with two types of afferent synapses: excitatory and unmodifiable inhibitory synapses.[{{Cite journal|last1=Marr|first1=D.|last2=Brindley|first2=Giles Skey|date=1971-07-01|title=Simple memory: a theory for archicortex|journal= Philosophical Transactions of the Royal Society B: Biological Sciences|volume=262|issue=841|pages=23–81|doi=10.1098/rstb.1971.0078|pmid=4399412|bibcode=1971RSPTB.262...23M|doi-access=}}] Memorizing cell inhibition serves two functions: one is controlling synaptic modification conditions in the memorizing cell dendrites during learning, and the other is controlling cell thresholds during recall.