In fact, from birth through late adolescence, the brain appears to add billions of new cells, literally constructing its circuits out of freshly made neurons as children and teenagers interact with their environments. In adulthood, the process of adding new cells slows down but does not stop.
Mature circuits appear to be maintained by new cell growth well into old age.
If these findings hold up to further scrutiny, the next decade of brain research promises to generate a total revision of how scientists think human minds are organized and constructed. Findings have already shed new light on mechanisms of learning, memory and aging in normal brains and suggest daring new ways to treat strokes and other brain disorders. Some researchers have begun isolating special cells that continue to divide and produce new brain tissue, with the hope of implanting such cells into areas of the brain that are damaged by disease or accidents. For decades, it was axiomatic that people were born with all the brain cells they would ever have. Unlike the bones, the skin, the blood vessels and other body parts, where cells divide throughout life to give rise to new cells, it was believed that the brain did not renew itself.