The neocortex is a part of the brain that is responsible for higher-order brain functions such as sensory perception, cognition, generation of motor commands, spatial reasoning, and language. It is the newest part of the cerebral cortex to evolve and is often described as being arranged in vertical structures called cortical columns. The neocortex comprises the largest part of the cerebral cortex and makes up approximately half the volume of the human brain. It is further subdivided into the true isocortex and the proisocortex. The neocortex is a complex brain structure that commands higher functions, such as sensory perception, emotion, and cognition. The molecular and genetic mechanisms of neocortex development are responsible for sensation, action, cognition, and other complex behaviors exhibited by mammals, including humans. The evolution of the neocortex in mammals is involved in volitional motor control, perception, cognition, and other complex behaviors exhibited by mammals, including humans.