Cerebral cortex

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Zhang & Sejnowski (2000)
Power law relationship between cortical white matter and gray matter across 56 species of mammals.

The cerebral cortex represents the outermost tissue layers within the telencephalon (aka as cerebrum) of vertebrates. It can be subdivided into the neocortex, the hippocampal formation and the olfactory cortex. Together with the basal ganglia, the cerebral cortex forms the gray matter of the brain which contains large numbers of nerve cell bodies and is connected by white matter, characterized by myelinated nerve fibres. In reptiles, the cortex consists of three layers, in mammals of six. In larger mammals, it is folded into gyri and sulci which increases the cortical surface area relative to the cortical volume — a process known as gyrification. The thickness of the cerebral cortex varies between different regions, with values from around 2mm to 4mm being normal in mammals. Changes in cortical thickness correlate with both brain maturation and aging and are especially pronounced in dementia.

Ontogeny

Three main processes govern the development of the cerebral cortex: proliferation of neural progenitor cells, neuronal migration and the establishment of brain connectivity via synaptic pruning and myelination. These processes are most important during fetal and early postnatal development but continue throughout life, with a second maximum during adolescence, particularly in the forebrain.