The human brain reaches its adult volume by age 10, but the neurons that make it up continue to change for years after that. The connections between neighboring neurons get pruned back, as new links emerge between more widely separated areas of the brain.
Eventually this reshaping slows, a sign that the brain is maturing. But it happens at different rates in different parts of the brain.
The pruning in the occipital lobe, at the back of the brain, tapers off by age 20. In the frontal lobe, in the front of the brain, new links are still forming at age 30, if not beyond.
“It challenges the notion of what ‘done’ really means,” Dr. Somerville said.