Right around the time of puberty and on into the adult years is a particularly
critical time for the brain sculpting to take place. Much like Michelangelo's
David, you start out with a huge block of granite at the peak at the puberty
years. Then the art is created by removing pieces of the granite, and that is
the way the brain also sculpts itself. Bigger isn't necessarily better, or else
the peak in brain function would occur at age 11 or 12. ... The advances come
from actually taking away and pruning down of certain connections themselves.
The frontal lobe is often called the CEO, or the executive of the brain. It's
involved in things like planning and strategizing and organizing, initiating
attention and stopping and starting and shifting attention. It's a part of the
brain that most separates man from beast, if you will. That is the part of the
brain that has changed most in our human evolution, and a part of the brain
that allows us to conduct philosophy and to think about thinking and to think
about our place in the universe. ...
I think that [in the teen years, this] part of the brain that is helping
organization, planning and strategizing is not done being built yet ... [It's]
not that the teens are stupid or incapable of [things]. It's sort of unfair to
expect them to have adult levels of organizational skills or decision making
before their brain is finished being built. ...
It's also a particularly cruel irony of nature, I think, that right at this
time when the brain is most vulnerable is also the time when teens are most
likely to experiment with drugs or alcohol. Sometimes when I'm working with
teens, I actually show them these brain development curves, how they peak at
puberty and then prune down and try to reason with them that if they're doing
drugs or alcohol that evening, it may not just be affecting their brains for
that night or even for that weekend, but for the next 80 years of their life.
Tell me a little bit about how the brain develops.
How does the brain -- arguably the most complicated three-pound mass of matter
in the known universe -- how does the brain become the brain? It does so
through two simple but powerful processes.
The first one is over-production. The brain produces way more cells and
connections than can possibly survive. There's only so many nutrients, there's
only so many growth factors, there's only so much room in the skull. After this
vast over-production, there is a fierce, competitive elimination, in which the
brain cells and connections fight it out for survival. Only a small percentage
of the cells and connections make it.
This is a process that we knew happened in the womb, maybe even the first 18
months of life. But it was only when we started following the same children by
scanning their brains at two-year intervals that we detected a second wave of
over-production. This second wave of over-production is manifest by an actual
thickening in the gray matter, or the thinking part, in the front part of the
As this second wave of over-production is occurring, it prepares the adolescent
brain for the challenges of entering the next stage of life, the adult years.
There's enormous potential at that time. People can take many different life
directions. But about around that time of puberty, people start specializing,
so to speak. They start deciding, "This is what I'm going to be good at,
whether it be sports or academics or art or music." All the life choices, even
though they are still there, start getting whittled away, and we have to start
sort of focusing in on what makes us unique and special. ...
Do you have particular concerns about that period, too, though?
Yes. It's a time of enormous opportunity and of enormous risk. And how the
teens spend their time seems to be particularly crucial. If the "Lose it or use
it" principle holds true, then the activities of the teen may help guide the
hard-wiring, actual physical connections in their brain. ...
Can you describe to me what people used to believe about the brain,
actually, very recently?
One of the most exciting discoveries from recent neuroscience research is how
incredibly plastic the human brain is. For a long time, we used to think that
the brain, because it's already 95 percent of adult size by age six, things
were largely set in place early in life. ... [There was the] saying. "Give me
your child, and by the age of five, I can make him a priest or a thief or a
[There was] this notion that things were largely set at fairly early ages. And
now we realize that isn't true; that even throughout childhood and even the
teen years, there's enormous capacity for change. We think that this capacity
for change is very empowering for teens. ...
This is an area of neuroscience that's receiving a great deal of attention ...
the forces that can guide this plasticity. How do we optimize the brain's
ability to learn? Are schools doing a good job? Are we as parents doing a good
job? And the challenge now is to ... bridging the gap between neuroscience and
practical advice for parents, teachers and society. We're not there yet, but
we're closer than ever, and it's really an exciting time in neuroscience. ...
The next step will be, what can you do about it, what can we do to help people?
What can we do to help the teen optimize the development of their own brain?
There has been a great deal of attention on the early years, and
particularly on stimulating the early brain. What do you think of that work and
that popularization of that brain science?
There's been a great deal of emphasis in the 1990s on the critical importance
of the first three years. I certainly applaud those efforts. But what happens
sometimes when an area is emphasized so much, is other areas are forgotten. And
even though the first 3 years are important, so are the next 16. And the ages
between 3 and 16, there's still enormous dynamic activity happening in brain
biology. I think that that might have been somewhat overlooked with the
emphasis on the early years. ...
Not so long ago, people were emphasizing teaching little children through
flashcards, through particular kinds of mobiles with black-and-white checks on
them, playing Mozart. In fact, some states have sent CDs back with new mothers.
What do you think of that? Has that been a misinterpretation of brain science?
... We all want to do the best for our children. And what I fear is happening
is that we're leaping too far from the neuroscience to such things. I don't
think there is any established videotape or CD or computer program or type of
music to play that we've shown with any scientific backing to actually help our
The more technical and more advanced the science becomes, often the more it
leads us back to some very basic tenets of spending loving, quality time with
our children. The brain is largely wired for social interaction and for bonding
with caretakers. And sometimes it's even disappointing to people that, with all
the science and all the advances the best advice we can give is things that our
grandmother could have told us generations ago: to spend loving, quality time
with our children. ... I think [it] probably does more harm than good for
parents to be confronted with so many of these conflicting reports in the media
without any scientific basis. ...
What directions is the research taking to explore how we can optimize brain
Now that we've been able to detect the developmental path of different parts of
the brain, the next phase of our research is to try to understand what
influences these brain development paths. Is it nutrient or parenting or video
games or the activity of the [child]? Or is it genes? By studying twins, we can
begin to address some of these very basic nature/nurture-type of questions.
For instance, when twins are in the first grade, their parents often dress them
in the same clothes. They get the same haircut. It's sort of cute how alike
they are. But that's not as cool in high school anymore. And so a lot of the
twins as teens in high school start doing different things. The one who was a
little bit better in sports may become an athlete. The one who was a little bit
better at academics may become a scholar. Or one may turn to music and one to
art. But they often have different daily activities.
So we can scan the brains when the twins are young and doing everything very
much alike; then we can scan them as teenagers, when they start having
different daily activities. This gives us a sense of which parts of the brain
are influenced by behavior and which parts by the genes themselves.
We've already got some interesting early data on this. One part of the brain is
called the corpus callosum. It's a thick cable of nerves that connects that two
halves of the brain and is involved in creativity and higher type of thinking.
It's very popular for imaging studies because it leaps out of the picture. It's
very easy to measure and quantify.
It's also interesting because it changes a lot throughout childhood and
adolescence. It's been reported to be different in size and shape in many
different illnesses that happen during childhood ... many higher cognitive
thought [processes] like creativity and ability to solve problems. So it's been
of great interest, especially to child psychiatrists. And what we find is that
the size and shape of the corpus callosum is remarkably similar amongst twins
... and [so] seems to be surprisingly under the control of the genes.
But another part of the brain -- the cerebellum, in the back of the brain -- is
not very genetically controlled. Identical twins' cerebellum are no more alike
than non-identical twins. So we think this part of the brain is very
susceptible to the environment. And interestingly, it's a part of the brain
that changes most during the teen years. This part of the brain has not
finished growing well into the early 20s, even. The cerebellum used to be
thought to be involved in the coordination of our muscles. So if your
cerebellum is working well, you were graceful, a good dancer, a good athlete.
But we now know it's also involved in coordination of our cognitive processes,
our thinking processes. Just like one can be physically clumsy, one can be kind
of mentally clumsy. And this ability to smooth out all the different
intellectual processes to navigate the complicated social life of the teen and
to get through these things smoothly and gracefully instead of lurching ...
seems to be a function of the cerebellum.
And so we think it's intriguing that we see all these dynamic changes in the
cerebellum taking place during the teen years, along with the changes in the
behaviors that the cerebellum sub-serves.
What would influence the development of the cerebellum?
Traditionally it was thought that physical activity would most influence the
cerebellum, and that's still one of the leading thoughts. It actually raises
thoughts about, as a society, we're less active than we ever have been in the
history of humanity. We're good with our thumbs and video games and such. But
as far as actual physical activity, running, jumping, playing, children are
doing less and less of that, and we wonder, long term, whether that may have an
effect on the development of the cerebellum.
The recess and play seems to be the first thing that is cut out of school
curriculums in tight times. But those actually may be as important, or maybe
even more important, than some of the academic subjects that the children are
doing. ... We think that the "Use it or lose it" principle holds for the
cerebellum as well. If the cerebellum is exercised and used, both for physical
activity but also for cognitive activities, that it will enhance its
... One analogy that computer people use is that [the cerebellum is] like a
math co-processor. It's not essential for any activity. People can get by quite
well without large chunks of it. But it makes many activities better. The more
complicated the activity, the more we call upon the cerebellum to help us solve
the problem. And so almost anything that one can think of as higher thought --
mathematics, music, philosophy, decision making, social skills -- seems to draw
upon the cerebellum. ...
The relationship between the findings that we have in the cerebellum and sort
of practical advice or the links between behavior are not well worked out yet.
That's going to be one of the great challenges of neuroscience -- to go from
these neuroscience facts to useful information for parents, for teachers or for
society. But it's just so recently that we've been able to capture the
cerebellum that no work has yet been done on the forces that will shape the
cerebellum or the link between the cerebellum shape or size and function.
When you look at the recent work that you've done in terms of the frontal
cortex, do you see a difference between girls and boys?
Yes. One of the things that we're particularly interested in as child
psychiatrists is the difference between boys' brains and girls' brains, because
nearly everything that we look at as child psychiatrists is different between
boys and girls -- different ages of onset, different symptoms, different
prevalences and outcomes. Almost everything in childhood is more common in boys
-- autism, dyslexia, learning disabilities, ADHD, Tourette's syndrome -- are all more common in boys. Only anorexia nervosa is more common in girls.
So we wonder if the differences between boys' and girls' brains might help
explain some of these clinical differences.
The male brain is about 10 percent larger than the female brain across all the
stages of ... 3 to 20; not to imply that the increased size implies any sort of
advantage, because it doesn't. The IQs are very similar. But there are
differences between the boy and girl brains, both in the size of certain
structures and in their developmental path. The basal ganglia which are a part
of the brain that help the frontal lobe do executive functioning are larger in
females, and this is a part of the brain that is often smaller in the childhood
illnesses. I mentioned, such as ADD and Tourette's syndrome.
So girls, by virtue of having larger basal ganglia, may be afforded some
protection against these illnesses. But in the general trend for brain
maturation, it's that girls' brains mature earlier than boys' brains. ...
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