Age matters. In children, myelin arrives in a series of waves, some of them determined by genes, some dependent on activity. The waves last into our thirties, creating critical periods during which time the brain is extraordinarily receptive to learning new skills. Thereafter we continue to experience a net gain of myelin until around the age of fifty, when the balance tips toward loss. We retain the ability to myelinate throughout life—thankfully, 5 percent of our oligos remain immature, always ready to answer the call.
