| Archicortex | |
|---|---|
.png) The archicortex in humans is a synonym of thehippocampal formation. The hippocampal formation is shown here, as drawn bySantiago Ramon y Cajal: DG: dentate gyrus. Sub: subiculum. EC: entorhinal cortex. CA1-CA3: hippocampus proper | |
| Details | |
| Part of | cerebral cortex orpallium |
| System | Olfactory system |
| Identifiers | |
| Latin | archicortex |
| NeuroNames | 170 |
| NeuroLex ID | birnlex_715 |
| TA98 | A14.1.09.302 |
| TA2 | 5530 |
| TE | E5.14.3.4.3.1.31 E5.14.3.4.3.1.32, E5.14.3.4.3.1.31 |
| FMA | 62424 |
| Anatomical terms of neuroanatomy | |
Thearchicortex, orarchipallium, is thephylogenetically second oldest region of thebrain'scerebral cortex (the oldest is thepaleocortex). In older species, such as fish, the archipallium makes up most of thecerebrum.Amphibians develop an archipallium andpaleopallium.
In humans, the archicortex makes up the threecortical layers of thehippocampus.[1] It has fewercortical layers than both theneocortex, which has six, and thepaleocortex, which has either four or five. The archicortex, along with the paleocortex andperiallocortex, is a subtype ofallocortex.[2] Because the number of cortical layers that make up a type of cortical tissue seems to be directly proportional[clarification needed] to both the information-processing capabilities of that tissue and itsphylogenetic age, the archicortex is thought to be the oldest and most basic type of cortical tissue.[3]
The archicortex is most prevalent in theolfactory cortex and thehippocampus,[4] which are responsible for processing smells and forming memories, respectively.[5] Because olfaction is considered to be the phylogenetically oldest sensory modality,[6] and thelimbic system, of which the hippocampus is a part, is one of the oldest systems in the brain,[7] it is likely that the archicortex was one of the first types of tissue to develop in primitivenervous systems.[7]
Archicortical precursor cells are also present in thedentate gyrus of the developingmammalianembryo.[8]
The archicortex is largely made up of memorizing cells with two types of afferent synapses: excitatory and unmodifiable inhibitory synapses.[9] 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.[9] Unlike theneocortex, the archicortex lacks climbing fibers (fibers involved in the clustering part of neocortical classification).[9] Consequently, the archicortex is not adapted for this type of classification.[9]
Unlike the neocortex, current theories of the archicortex argue that it performs simple memorization without changing the input's format in any complex manner.[9] The archicortex is unable to classify inputs. It has two main uses: free simple memory and directed simple memory.[9]
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