Cerebral Cortex - Classification

Classification

Based on the differences in lamination the cerebral cortex can be classified into two major groups:

• Isocortex (neocortex or homogenetic cortex), the part of the mature cerebral cortex with six distinct layers (homotypic cortex), or that passes through a six-layered stage during development to have more or less than six layers (heterotypic cortex) in the mature brain. Examples of heterotypic isocortex are agranular area 4 of Brodmann and striate area 17 of Brodmann.
• Allocortex (or heterogenetic cortex), the part of the cerebral cortex with less than six layers (varying in number). Examples of allocortex are the olfactory cortex and the hippocampus.

Auxiliary classes are:

• Mesocortex, classification between isocortex and allocortex where layers 2, 3, and 4 are merged
• Proisocortex, Brodmann areas 24, 25, 32
• Periallocortex, comprising cortical areas adjacent to allocortex.

Based on supposed developmental differences the following classification also appears:

• Neocortex or Neopallium, which corresponds to the isocortex.
• Archicortex, which phylogenetically is the oldest cortex
• Paleocortex

In addition, cortex may be classified on the basis of gross topographical conventions into four lobes: the Temporal lobe, Occipital lobe, Parietal lobe and Frontal lobe: