The term neocortex refers to one of two types of cerebral cortex defined on the basis of cytoarchitecture and fetal development. The other is allocortex. Neocortical areas pass through a six-layered stage in the third semester of gestation. Most retain six layers into adulthood and are called homotypic cortex. A few undergo modification to more or less than six layers and are called heterotypic cortex. Starting from the cortical surface the basic layers are: molecular layer of the cerebral cortex (I), external granular layer (II), external pyramidal layer (III), internal granular layer (IV), internal pyramidal layer (V), and multiform layer (VI). neocortex is most prominent in the frontal lobe, the parietal lobe, the temporal lobe and the occipital lobe, less so in the cingulate gyrus, the parahippocampal gyrus and the insula. Also known as 'isocortex', the neocortex is composed of two subdivisions: true isocortex and proisocortex ( Carpenter-1983 ). In the human it constitutes 96% of the surface area of the cerebral cortex ( Zilles-1990 ),