Page "Cerebral cortex" Paragraph 2

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, called " sulci ".

The phylogenetically most recent part of the cerebral cortex, the neocortex ( also called isocortex ), is differentiated into six horizontal layers ; the more ancient part of the cerebral cortex, the hippocampus ( also called archicortex ), has at most three cellular layers, and is divided into subfields.

Neurons in various layers connect vertically to form small microcircuits, called columns.

Different neocortical architectonic fields are distinguished upon variations in the thickness of these layers, their predominant cell type and other factors such as neurochemical markers.