contd. from

Why is it that you may know more about adults than children? Is the brain not yet developed? And when is it fully developed?

No. There are some studies that can't be done in children, because the regulations that we work under require that we limit the level of risk to negligible levels, especially if we're going to be studying healthy children as control subjects. So we have to think of other ways to get indirect information.

But the brain is constantly evolving... . And it changes dramatically from childhood, to puberty, to adulthood. Can't you outgrow ADHD?

The manifestations of ADHD change with age. And so I think some individuals can be said to outgrow their ADHD. It used to be believed that all kids with ADHD would outgrow it. And now we also know that that's not true. For some people, they continued to have difficulties, whether it's in high school, or college, or at work, or with relationships. But it's not everyone. A significant proportion get better . We don't know what the proportion is, because we'd need a very large study, and we'd need to follow people over a long period of time. ...

I hear you say that there are a lot of limitations in what you know. Why are there so many limitations?

Well, there are limitations because we've only just started. Until about 10 years ago, we couldn't really quantify or measure anything in the brain, especially in children. And so we had to rely on impressions. If you go back and look at the journals that were written in the 1960s, 1970s, 1980s, some of them were almost like novels. They're very rich with detail and texture, but have very few numbers. And until you could start counting things, or measuring them, it's hard to really make progress. Once we had magnetic resonance imaging and other sorts of techniques like that, we're able to start measuring and studying the brain.

... When I get discouraged, I think about a map that I have in my house that came from an exhibit in the Smithsonian from 1500. It's a map of the New World, and you can tell that they knew about Florida--there's a peninsula. They have an idea about the East Coast, and even Texas, but you wouldn't want to use that to drive from Tallahassee to Atlanta, because it's just too crude. So we're about at that level of getting an idea of where the major pieces are, and what their relationships may be. And it's better than it used to be. But we've only been at it for about 10 or 12 years. ...

... Give me one true fact about ADHD.

The posterior inferior vermis of the cerebellum is smaller in ADHD. I think that that is a true fact. It's taken about five years to convince myself that that's the case. That's about as much as I know--that I'm confident about.

What does that mean?

I don't know what it means, but it's true, and it's a fact. And that's the next step.

So show me a bit about how it works in the brain.

... Even though it's only about 10 percent of the size of the total brain, there are more neurons in the cerebellum than in the entire rest of the brain combined, which is fascinating. But the cerebellum has never been thought to be that important, because you can remove it, and nothing terrible happens. But recently, people have noticed that the cerebellum is very involved.

One person says that the cerebellum is a little bit like a co-processor--it's useful, but it's not necessary. And he believes that its function is really to help the other parts of the brain work better. That makes some sense to me, that maybe that's what's not working so well in ADHD. People with ADHD can do anything; they just don't do it quite so well. It's a disorder of efficiency, or inefficiency, as much as anything, I believe. I'm excited about the possibility that this is an important clue to understanding this. But how to build on that is something that I'm still struggling with. ...

What is a question that you're trying to answer in your research?

I'm also involved in collecting samples for genetic analysis, to see if we can find what genes increase the risk that someone's going to have ADHD. We know that it's not likely to be a simple association between a gene and the disorder. But likely, almost certainly, genes do influence how hyperactive, how impulsive, how inattentive someone is. And that's a long-term kind of project. I'd like to think of some newer ways of imaging the brain in children, to see if we can see the functioning of the brain. But those are perhaps a year or two away.

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Written 2000. Reviewed: 02/2006