Allocortex

ALLOCORTEX, phylogenetically the oldest part of the cerebral cortex, including the olfactory cortex and the Ammon's horn. In the process of ontogenetic development, it does not pass through the six-layered stage characteristic of the rest of the cortex - isocortex. According to Brodmann, this heterogeneous cortex breaks down into the following parts: 1) cortex primitivus, which does not have six layers - bulbus, pedunculus olf. and others, 2) cortex rudimentarius with rudimentary layers - hippocampus, fascia dentata and others, and 3) cortex striatus - Brodmann fields 27, 28, 34, 35, 48, 51. - Gyrus cinguli does not belong here, except for its isthmus. According to microscopic structure, some parts of A. differ in their rudimentary nature; in others, on myelin preparations, it is visible that the radial fibers reach the 1st layer (supraradial type), and partly to the middle of the 5th (infraradial type). A more detailed division of A. into parts and areas was made by the Vogts (C. and O. Vogt), as well as Economo and Koskinas. Area cortex and literature - see Architectonics of the cerebral cortex.

Figure 1. Boundaries of the allo- and isocortex on the orbital surface of the right frontal lobe (Allocortex - inside the line marked with large black dots). The top corresponds to the anterior, and the bottom to the posterior sections. Re, OF¹ and OF* are located laterally. The insula approaches from the back left. Thio-Tuber (trigonum) olf.; Tb¹ and Tb²-tuberculum olf.; S. per/, a.-subst. perforata ant. (small divisions and designations refer to the areal structure according to Vogt).

rudimentarily; in another, on myelin preparations, it is visible that the radial fibers reach the 1st layer (supraradial

Figure 2. Boundaries of the allo- and isocortex on the inner surface of the right hemisphere (Allocortex - inside the midline marked with black dots). Amb-gyrus ambiens; Cc-corpus callosum; F-Fornix; H-gyrus hippocampi; L-gyrus parahippocampalis; Lj-isthmus; sem-gyrus semilunaris.

type), partly - to the middle of the 5th (infraradial type). A more detailed division of A. into parts and areas was made by the Vogts (C. and O. Vogt), as well as Economo and Koskinas. Area cortex and literature - see Architectonics of the cerebral cortex.