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The neocortex (Latin for "new bark" or "new rind"), also called the neopallium ("new mantle") and isocortex ("equal rind"), is a part of the mammalian brain. In the human brain, it is the largest part of the cerebral cortex which covers the two cerebral hemispheres, with the allocortex making up the rest. The neocortex is made up of six layers, labelled from the outer in, I to VI. In humans, the neocortex is involved in higher functions such as sensory perception, generation of motor commands, spatial reasoning, conscious thought and language. There are two types of cortex in the neocortex – the true isocortex and the proisocortex. ==Anatomy== The neocortex is the most developed of the cerebral tissues. The neocortex consists of the grey matter, or neuronal cell bodies and unmyelinated fibers, surrounding the deeper white matter (myelinated axons) in the cerebrum. There are two types of cortex in the neocortex, the proisocortex and the true isocortex. The ''pro-isocortex'' is a transitional area between the ''true isocortex'', and the periallocortex (part of the allocortex). It is found in the cingulate cortex (part of the limbic system), in Brodmann's areas 24, 25, 30 and 32, the insula and the parahippocampal gyrus. The neocortex is smooth in rodents and other small mammals, whereas in primates and other larger mammals it has deep grooves (sulci) and ridges (gyri). These folds allow the surface area of the neocortex to increase far beyond what could otherwise be fit in the same size skull. All human brains have the same overall pattern of main gyri and sulci, although they differ in detail from one person to another. The mechanism by which the gyri form during embryogenesis is not entirely clear, and there are several competing hypotheses that explain gyrification. Axonal tension, cortical buckling, or differences in cellular proliferation rates in different areas of the cortex during embryonic development may contribute to the formation of gyri. The neocortex contains two primary types of neurons, excitatory pyramidal neurons (~80% of neocortical neurons) and inhibitory interneurons (~20%). The structure of the neocortex is relatively uniform (hence the alternative names "iso-" and "homotypic" cortex), consisting of six horizontal layers segregated principally by cell type and neuronal connections. However, there are many exceptions to this uniformity; for example, the motor cortex lacks layer IV. There is some canonical circuitry within the cortex; for example, pyramidal neurons in the upper layers II and III project their axons to other areas of neocortex, while those in the deeper layers V and VI project primarily out of the cortex, e.g. to the thalamus, brainstem, and spinal cord. Neurons in layer IV receive all of the synaptic connections from outside the cortex (mostly from thalamus), and themselves make short-range, local connections to other cortical layers.〔 Thus, layer IV receives all incoming sensory information and distributes it to the other layers for further processing. The neurons of the neocortex are also arranged in vertical structures called cortical columns. These are patches of the neocortex with a diameter of about 0.5 mm (and a depth of 2 mm). Each column typically responds to a sensory stimulus representing a certain body part or region of sound or vision. These columns are similar, and can be thought of as the basic repeating functional units of the neocortex. In humans, the neocortex consists of about a half-million of these columns, each of which contains approximately 70,000 neurons.〔bluebrain.epfl.ch〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「neocortex」の詳細全文を読む スポンサード リンク
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