What is Cerebral cortex?
[[File:Brain 2.jpg|thumb|right|220px|Different parts of the cortex <br>have different functions]] The '''cerebral cortex''' is the most important part of the [[brain]]. In humans, it is by far the largest part of the brain. Though this cannot be seen directly, different parts of the cortex have different functions (see diagram). It plays a key role in [[memory]], [[wikt:attention|attention]], perceptual [[wikt:aware|awareness]], [[thought]], [[language]], and [[consciousness]]. It is a sheet of neural [[tissue]] that is outermost to the [[cerebrum]] of the mammalian [[brain]].<ref>The cerebrum is the forebrain of vertebrates.</ref> It has up to six layers of nerve cells. The human cerebral cortex is 2–4&nbsp;mm (0.08–0.16&nbsp;inches) thick. In preserved brains, it is [[grey]], so it is often called '[[grey matter]]'. In contrast to gray matter that is formed from [[neurons]] and their [[myelin|unmyelinated]] fibers, the [[white matter]] below them is formed predominantly by myelinated [[axon]]s interconnecting [[Neuron|neurons]] in different regions of the cerebral cortex with each other and neurons in other parts of the [[central nervous system]]. The surface of the cerebral cortex is folded in large mammals, such that more than two-thirds of it in the [[human brain]] is buried in the grooves. == Neocortex == The [[phylogenetics|phylogenetically]] most recent part of the cerebral cortex, the '''neocortex''', has six horizontal layers; the more ancient part of the cerebral cortex, the [[hippocampus]], has at most three cellular layers. Neurons in various layers connect vertically to form small microcircuits, called 'columns'. The neocortex is the newest part of the cerebral cortex to [[Evolution|evolve]]. The six-layer neocortex is a distinguishing feature of [[mammal]]s; it has been found in the brains of all mammals, but not in any other animals. In humans, 90% of the cerebral cortex is neocortex. == Allocortex == Other parts of the cerebral cortex are: *Allocortex: fewer than six layers, more ancient