The allocortex (also known as heterogenetic cortex) is one of the two types of cerebral cortex, the other being the neocortex. It is characterized by having just three or four cell layers, in contrast with the six layers of the neocortex, and takes up a much smaller area than the neocortex. There are three subtypes of allocortex: the paleocortex, the archicortex, and the periallocortex – a transitional zone between the neocortex and the allocortex.
The specific regions of the brain usually described as belonging to the allocortex are the olfactory system, and the hippocampus.
Allocortex is termed heterogenetic cortex, because during development it never has the six-layered architecture of homogenetic neocortex. It differs from heterotypic cortex, a type of cerebral cortex, which during prenatal development, passes through a six-layered stage to have fewer layers, such as in Brodmann area 4 that lacks granule cells.