The neocortex is a more advanced cortex.It is the most part of the mammalian cerebral cortex, located at the top layer of the cerebral hemisphere, about 2-4 mm thick, and divided into six layers.It is related to some higher functions such as perception, the generation of motion commands, spatial reasoning, consciousness and human language.
The cerebral cortex is the gray matter covering the two hemispheres of the brain. It is the material basis of advanced neural activities and is composed of neurons, nerve fibers and glia.There are a lot of wrinkles on the human cerebral cortex, called gyri, the shallow space between gyri is called sulcus, and the deep and wide sulcus is called fissure.The area of sulcus and gyrus increased the area of cortex.The surface of cerebral cortex is divided into five lobes——frontal lobe、parietal lobe、Temporal lobe, occipital lobe and marginal lobe.The frontal lobe, parietal lobe, temporal lobe and occipital lobe appear later in the system, which is called neocortex, and the marginal lobe occurs earlier, which is called old cortex.The cerebral cortex is divided into six layers from the outside to the inside: the molecular layer, the outer granular layer, the pyramidal cell layer, the inner granular layer, the ganglion cell layer, and the polytype cell layer. They are composed of different types of nerve cells. The granular cells receive sensory signals, and the pyramidal cells transmit motor information.
Paleocortex
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The paleocortex is the oldest cortex in evolution.This includes the cortex that forms the hippocampus and dentate gyrus.[1]
Old cortex
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The old cortex is an ancient cortex.It is the cortex that makes up the olfactory brain.Together with the ancient cortex, it is called the marginal cortex, and together with the amygdala, the septal nucleus and the hypothalamus, which are closely related to it, it is called the limbic system of the brain.
Morphological structure and classification of neocortex
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Neocortex is the latest cerebral cortex in the evolution process.Occupying most of the surface of the cerebral hemisphere, it has a typical 6-layer structure in cellular architecture, also known as homotypic cortex, and is the highest regulatory center of the whole body.In mammals, the higher the grade, the more developed the neocortex.The neocortex is divided into frontal lobe, parietal lobe, occipital lobe and temporal lobe according to its location and function. The frontal lobe is mainly related to movement, while the parietal lobe is related to sensation. The occipital lobe and temporal lobe are visual and auditory centers respectively.
anatomic structure
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1. Neocortex:
The gray matter covered by the telencephalon surface is called cerebral cortex, or neocortex.According to evolution, the cerebral cortex is divided into ancient cortex, old cortex and new cortex.The ancient cortex and the old cortex are related to the sense of smell, and are collectively called olfactory brain.In mammals, the higher the grade, the more developed the neocortex.The ancient and old cortex are three layers of cortex, while the new cortex develops into six layers.Due to the highly developed human neocortex, it accounts for about 96% of the total cortex.The thickness of each area of the cerebral cortex varies, for example, the anterior central gyrus is 4.5 mm, and the visual area of the occipital lobe is only 1.5 mm.The size, shape and density of nerve cells in each layer of cortex are also different.At 7-9 months of human embryo, all parts of cortex are six layers.Therefore, the cortex of the six layer type can be regarded as the basic type, and most adult cortices maintain this type.
2. Cerebral cortex:
The cerebral cortex is a layer of gray matter, which forms the surface layer of the sulci and gyri of the cerebral hemisphere. It is the most important part of the brain and the material basis of high-level neural activities.The volume of the human cerebral cortex is about 300 cubic centimeters, and the total area is about 2200 square centimeters.Among them, 1/3 is exposed on the surface and 2/3 is located on the trench wall and bottom.The average thickness of the cortex is 2.5 mm. The anterior central gyrus is the thickest, about 4.5 mm, while the cortex at the occipital pole is the thinnest, about 1.5 mm.There are two main components in the cerebral cortex, one is cells, including the cell body of neurons and glia;The other is nerve fiber.
3. Paleocortex:
The paleocortex belongs to allogenic cortex, which is only found in the hippocampal formation and is basically composed of three layers of cells.The hippocampal formation is the part of the medial edge of the cerebral cortex.Due to the extreme development of neocortex, this cortex is pushed to the medial side of the cerebral hemisphere.Between the hippocampal fissure and the choroid fissure, it bends downward with the development of the temporal lobe, and then turns forward, from the interventricular foramen to the tip of the lower horn of the lateral ventricle, forming an arcuate gray matter area, including part of the superior gyrus of the corpus callosum, fascicular gyrus, dentate gyrus, hippocampus, lower crus, and hook of the hippocampal gyrus.
4. Old cortex:
The old cortex, including the anterior piriform area and the entorhinal area, also belongs to the allocortex, and is basically composed of three layers of cells.However, sublayers appear in many regions, forming six layers similar to the isocortex, while the cell types in the cortex are less, for example, Golgi II cells are much different from the neocortex.
