New neuroscience research has shown that a crucial part of the brain undergoes extensive changes during puberty. It’s long been known that the architecture of the brain is largely set in place during the first few years of life. But with the aid of new technologies such as magnetic resonance imaging (MRI), scientists are mapping changes in pre-teen and teenage brains and finding evidence that remarkable growth and change continue for decades.

Confronted by these new discoveries, academics, counselors, and scientists are divided on just what all this means for children.”Our leading hypothesis … is the ‘use it or lose it’ principle,” neuroscientist Jay Giedd tells Frontline. “If a teen is doing music or sports or academics, those are the cells and connections that will be hardwired. If they’re lying on the couch or playing video games or [watching] MTV, those are the cells and connections that are going to survive.”

But others voice caution in leaping to conclusions about the implications of these findings.

“The relationship between desired behaviors and brain structure is totally unknown,” John Bruer tells FRONTLINE. He is president of the James S. McDonnell Foundation and author of The Myth of the First Three Years. “This simple, popular, newsweekly-magazine idea that adolescents are difficult because their frontal lobes aren’t mature is one we should be very cautious of.”

Despite all the new scientific research, “Inside the Teenage Brain” suggests that there is a consensus among experts that the most beneficial thing for teenagers is good relationships with their parents.

Ellen Galinsky, a social scientist and the president of the Families and Work Institute, told FRONTLINE, “Even though the public perception is about building bigger and better brains, what the research shows is that it’s the relationships, it’s the connections, it’s the people in children’s lives who make the biggest difference.