Latter goes on to become nervous tissue of brain and spinal cord and skin. Nerve and glial cells for all parts are generated via mitosis in the ventricular zone. Each cell in proliferative region produces a fixed number of daughter cells that then migrate out. Each cell in proliferative zone produces a fixed number of daughter cells that then migrate out. Factors that fix number are unknown.
Later borns migrate past earlier born cells.
Last layer of cortex consists of last born neurons. Whole cortex is about 100 cells thick but regional differences. This process amounts to the wiring of the brain. As indicated earlier, the brain at birth has an abundance of neurons and a paucity of interconnections. Much of the prenatal and post-natal development of importance involves the formation of synapses.