The white matter, also known as myelin, acts like the insulation on an electric cord, allowing electrical impulses to travel down a nerve faster and more efficiently. It now appears that many of the nerves connecting different processing centers in the brain don't finish myelinating until the early 20s. Some of the nerves that become sheathed during adolescence connect areas of the brain that regulate emotion, judgment, and impulse control. Francine Benes, a neuroscientist at McLean Hospital, says that these nerves myelinate in girls earlier than in boys, which may help explain why teenage girls seem more emotionally mature than boys, whose myelin levels may not equal girls' until age 30. The myelination process also has been implicated in schizophrenia, which often becomes apparent in late adolescence.
Benes believes the faster transmissions overload defective nerves in schizophrenics.
If the circuit starts to have too much information coming in too rapidly, it may become overwhelmed. Researchers feel they have only begun to probe the workings of the adolescent brain, but their findings already offer some new ways for parents to deal with teenagers. During adolescence, many higher mental skills will become automatic, just the way playing tennis and driving do. Kids who exercise their brains, in effect, by learning to marshal their thoughts, to measure their impulses, and to understand abstract concepts, are laying the neural foundations that will serve them for the rest of their lives. You are hard-wiring your brain in adolescence.