Neocortex: The newer portion of the cerebral cortex that serves as the center of higher mental functions for humans. The neocortex contains some 100 billion cells, each with 1,000 to 10,000 synapses (connections), and has roughly 100 million meters of wiring, all packed into a structure the size and thickness of a formal dinner napkin. The cells in the neocortex are arranged in six layers, within which different regions permit vision, hearing, touch, the sense of balance, movement, emotional responses and every other feat of cognition.