Studying teens from the inside out
Jay Giedd uses magnetic resonance imaging to study the adolescent brain.
Imster: Do you have a teenager?
Giedd: I have a twelve-and-a-half year old, so I can pretend I’m an expert for a little bit longer. Because once I have my own, I’ll probably have no credibility in talking about teens.
Imster: Teenagers may look like adults from the outside of their heads, but the inside isn’t there yet, is that right?
Giedd: Yes. Particularly a part of the brain involved in controlling impulses, long term consequences, decision-making, the part of the brain that helps integrate all the information that is available to make the decisions.
Imster: This kind of research became possible in just the past few decades, with the development of new tools such as Magnetic Resonance Imaging, right?
Giedd: The advance of MRI is that is doesn’t use radiation, so you can scan kids safely, and not only scan them once, but scan them repeatedly over time.
Imster: And you can look at live brains…
Giedd: That was the real breakthrough. To follow living, growing brain in the same individuals over time really has been the key to understanding the path of development.
Before MRI, a lot of the studies on the brain had to guess what was happening inside. But the brain itself was literally called a “black box.” It was thought that not only couldn’t you look inside the black box, but it really wasn’t important because it was seen as inaccessible. MRI has really launched a new era of adolescent science because you can look at the living, growing human brain, not only its structure, but its activity. It’s really changed everything in terms of how people approach the study of the brain.
Imster: And what are you discovering about how the adolescent brain changes?
Giedd: The timing of all this was one of the first surprises. When we started the studies of childhood and adolescent development, we weren’t sure whether to go to age sixteen, or to age eighteen.
Piaget was still very popular when I was in college. He talked
about these levels of cognitive development — age twelve was the highest rung in the ladder – formal operations, thinking about thinking. And that never seemed right. Twelve-year-olds aren’t running the world, and they’re not at their peak intellectually. But by age eighteen, people can vote, and get married, and drive a car, and go to war and do all these adult things. We would have guessed that somewhere around there the brain would be pretty much in its finished state.
So we were surprised to see that these changes continue to go past age sixteen, past eighteen, and now if we had to say a number it would be closer to age twenty-five. That this whole concept of adolescence being stretched out longer, not just socially, but biologically was an important impact from the imaging studies.
Imster: How much effect does experience and environment have on each teenager’s brain development?
Giedd: That’s one of the prime questions that we’re trying to sort out. It may be that the essence of the brain’s job during the teen years is to change and adapt.
The brain biologically probably hasn’t changed a whole lot in the last ten thousand years, but what we do with it has enormously – from hunting and gathering berries, to talking on the phone, to working computers, and there’s no way the genes could have accounted for all these different possibilities. The key was to make a very plastic is one word or changeable, or adaptable brain.
And at this time — around age eleven in girls and twelve-and-a-half in boys — the gray matter is the thickest. We think that means it has the most connections. Each brain cell has connections, like a bush or a tree, lots of branches, twigs and roots.
Then from that peak, it starts pruning them away. We think that that’s the key the connections that are used a lot will survive and flourish, and those that are not used will whither and die.
Having this maximum flexibility right before entering this next stage of life means that the activities of the teen, or what’s
happening around them, may have a lot to say on the actual wiring or the connections. So it really makes it a powerful time in the person’s life because they have a lot of say in what they do with their time and their activities, but the biology really seems to have fostered this time when enormous change is possible.
Imster: When you look at brains with MRI, what looks different in a fifteen-year-old versus, say, a thirty-five year old brain?
Giedd: One of the things that an MRI can see is gray matter versus white matter.
Gray matter is the neuron cell body that has the DNA and the headquarters of the cells, and also the dendrites, which are antennae that reach out to communicate with other brain cells. And that looks gray on the MRI pictures.
The other thing you can see in the MRI pictures is white matter, which is a wrapping around the neurons that speed up the communication. With this wrapping, neurons can communicate one hundred times faster than without it. We see that throughout the teen years, you get more and more of this white matter. The speed of communication between the brain cells gets faster and faster. But the gray matter actually thins down, so that in a sense you have fewer but faster connections. So the fifteen-year-old would have, in a sense, more different possibilities, more different types of connections, but the thirty-year-old would have faster connections for those types of activities that were practiced or the time was spent on.
An analogy that’s often used is country road driving. The country road may be gravel and you can’t go that fast, but you can turn off every quarter of a mile, you have lots of options along the way. The roads that get used a lot may get paved, they even may become two-lanes. The roads that are used a great deal, maybe between two cities, may become a superhighway and have six or seven lanes you can zoom down. But now you can’t turn off every quarter of a mile any more you have to wait for exits and be in the right lane and that seems to be the trade-off. There are certain communications between brain cells that get faster and faster, but the price you pay is that you don’t have the flexibility that you had when you were younger.
Imster: How similar are these “maps” between individuals?
Giedd: Certain parts of the brain seem to be very alike in identical twins who share the same genes, the same DNA compared to fraternal twins? who only share half of their genes. And other parts don’t seem to be very connected to the genes.
That’s one of the areas we’re researching a lot trying to understand the link between genes, brain and behavior. Over half of our scans these days are twin either identical or non-identical twins. If we can understand what parts of the brain are driven by the genes, and what part by the environment, it can help guide our interventions. Because we can do something about the environment, and we can try to understand when the changes are occurring, so we can then know how to help in illnesses in which the brain development may be going awry.
Imster: So when you see my teenager suddenly being so forgetful, inattentive, it’s not just that he’s being contrary, it’s the manifestation of the natural development going on in his brain?
Giedd: As a parent, that is a helpful way to look it. The brain is so busy at these times. Because sometimes your teenager can come up with remarkable insights on one day you can have a conversation with him, and he’ll seem like an adult, and you’ll think, “Great! That stage has passed.” But then two days later, he’ll be childlike again. That’s what I think is so frustrating. The inconsistency is one of the hallmarks. We look at this as a time when the brain is trying to sort through all these options. The way that it learns is mostly by trial and error, and the error is not unnatural that’s how it’s supposed to be going. Teenagers are trying on some different identities whether they’re going to be a scholar or an athlete or musical it’s a process where they’re really trying to sort this out. The brain, I think, reflects that.
We just have to make sure the irreversible consequences don’t happen unwanted pregnancies, or car accidents or substance abuse that can lead to lasting changes. But without the more severe consequences, we should probably be fairly tolerant of the more minor missteps.
It’s frustrating for teenagers themselves sometimes as well. It seems as though this is all a choice and is all willful behavior that they’re choosing to be defiant or disobedient, when actually it’s more difficult for them to be organized.
Imster: In your research, you watch how brains change over time, so you see the same teenagers year after year. For your teenage subjects, do you think coming to you and seeing how their brain develops influences how their brain develops?
Giedd: We think it does, and in many ways we hope it does. One of the obvious examples is with substance abuse, and when we can show how much the brain is changing during these teen years and what a vulnerable time introducing substances, illegal substances, at this time, shows them why they should wait, or why the drugs of abuse may alter this pathway. We hope that for many of them, it will help them make different decisions. We think that it’s an area that could be done a lot better of informing parents and the teens themselves about the new brain development knowledge.
Imster: Do you talk to them about what you’re finding, and what is their response?
Giedd: Often they find it very empowering. Because unlike when they were babies and the brain was forming, now they have a lot of control over their activities and what they do with their time. Given that there is so much potential going on during these teen years, most of the teens we work with find this a very uplifting optimistic type of message – and rightfully so.
Imster: Where is your research going?
Giedd: The first thirteen years has really been to map brain development just to observe what the brain does, how it changes from childhood through adolescence into young adulthood. It’s been only 2004 when we were able to make these movies showing how these changes occur. The emphasis now is not just to map brain development, but to understand all the things that might have an impact whether that be parenting or school or diet or video games or drugs and alcohol. We’re just now at this threshold of being able to apply the technologies and the advances in genetics to take this next step, of not just observing, not just mapping, but to understanding the process.
Imster: You’ve been describing how brain is “plastic,” how humans have the ability – in adolescence and even later in life – to change our own brains to better adapt to our world.
Giedd: I think it’s the key ingredient to our success. If I had to say in a short sentence what the brain does: It adapts. The human brain is incredibly good at adapting to the environment. The extra part is, not only can we adapt to the environment, but we can change the environment. Other species can to some degree, but no other species to the degree that humans can – from living at the equator to living at the North Pole, even into outer space – and this ability to not only adapt to the environment but to actually change the environment is I think what has set us apart from the other species.
Imster: If one of the things brain does during adolescence is prepare itself for being an adult in the world, how do we know which things teenagers are doing that will be good for their brains and which activities won’t? Especially since the world is changing faster and faster between generations. For example, let’s take video games, will playing a lot of video games turn out to be helpful, harmful or benign for the future? Probably it wouldn’t have helped my grandmother be more successful in her world…
Giedd: She didn’t need keyboarding skills, and those sorts of skills that in the future may be actually quite valuable for understanding complex systems. Some of the games are quite complicated, many of the games require competition against other human users.
I often think that video games are like fire, or any other powerful tool. It can be used or misused or abused. It’s very easy to make a sweeping statement that they’re bad, they’re a waste of time, but I think it all depends of the specifics of the game. Because there’s software that helps kids read earlier, they can achieve math skills at earlier ages. It can really be an amazing way to captivate children’s imaginations and thinking. Or, software can be totally driven by sex and violence, and kids can spend hours and hours a day not interacting with other people because they’re wrapped up in the worlds of the video games. The difficulty is that the marketplace rewards the sex and violence more than it does the creative and intellectual type of programs.
But I think that it would be wrong to try to deny that most children and adolescents are going to be spending a lot of their time interacting with video games and other types of technologies. I think the goal should be to have more and more better programs, better games, as opposed to trying to curtail the activity.
And like so many of these things, moderation is the key. Especially for teens who have some difficulty with social interaction, it becomes a very easy escape or out that they can not leave home for the whole weekend and be wrapped up in the games, and I think that’s clearly excessive, because interacting with other humans is, I think, an important part of the way the brain develops.
Imster: Do other animal species have an adolescence?
*Giedd: Great question. It is very hard to find animal models of adolescence. There is certainly a period of puberty and so there is childhood. But after puberty, most of the other species look quite adult-like in the sense that they often start having babies soon after that point. The notable exception is the non-human primates they do have this period of adolescence that has a lot of parallels to humans. And it’s just beginning to become a very active area of investigation.
Imster: Thank you, Dr. Giedd.
Greetings Dr. Giedd,
I am writing to ask you if you can direct me to an article that I could reprint for two courses that our company offers. Our company provides gradutate distance learning courses for teachers and other education professionals. Currently, we are increasing the rigor of some of our courses and we would like to include an article on brain research and teens along with our course syllabi. The article would be provided as a convenience to teachers and we would receive no commercial gain.
Thank you for your time and consideration in this matter.
Sincerely,
Susanne Deitermann