"...two groups of scientists, one at UCLA and one at NIH, ... discovered, the frontal lobes (the seat of such high-level functions as judgment, emotional regulation and self-control, organization, and planning) experience a growth spurt, with gray matter proliferating almost as exuberantly as it did during gestation and infancy; the volume of gray matter increases noticeably, reflecting the formation of new connections and branches. And then, in a person's twenties, there is another reprise of the neurological events of early childhood, as unused synapses are eliminated so the networks that remain are more efficient. Other brain regions also remain under construction through adolescence. The parietal lobes, which assemble information that arrives from distant neighborhoods of the brain, are works in progress through the midteens. They continue to add gray matter until age ten (in girls) or twelve (in boys), after which underused synapses are pruned just as they are in childhood. Similarly, the temporal lobes, which contain matter until age sixteen and only then undergo pruning.
Contrary to the belief that wholesale neuronal birth and synapse formation occur only during gestation and infancy, then, the brain gets a second wind just before puberty. Describing these discoveries ... Neville said that "we've learned an astonishing thing in the past few years, and that is that the human brain -- in terms of the hardware, the number of synapses, the number of dendritic branchings -- doesn't look adultlike until twenty to twenty-five years after birth." Even a brain this ancient has the raw material for neuroplasticity. That suggests that those raw materials could be put to one of the same uses they were in childhood -- namely, giving the brain the malleability to respond to experience.
The fact that the brains of adolescents and young adults undergo such extensive synapse formation and pruning means that kids have a second chance. .... Synapses that support unused skill will wither like rosebushes targeted by a zealous gardener.
