The Adolescent Brain: A Work in Progress

Presenter: Pat Wolfe, Mind Matters, Inc., Napa, CA

This session is presented in separate parts. Use the buttons at the end of the transcription to navigate between each part.

Part One

PAT WOLFE: I have this theory. I was thinking last night, if anyone comes at 8 o'clock, they are going to be here for one of two reasons. One, they have an adolescent. How many of you have an adolescent?

[A show of hands]

I knew it. I knew it.

And the other reason would be that you teach an adolescent. How many of those? See, I knew it. And how many of you think you are still an adolescent?

[Laughter]

That makes sense.

A word of caution before we begin this morning. I am going to present some of the newest research on the adolescent brain. And it is really new research. But I want you to know that it is still ill-formed. A lot of this is theoretical. Not all the neuroscientists agree. I have tried to cull from a large number of sources and present that information that has a fair amount of consensus. So, I want you to take this with a grain of salt this morning.

Brain research is proliferating so fast we can hardly keep up with it. There are things that I wrote in my book, which has just been out a year, that I would have to greatly revise were I revising it today. Another caveat is to be very, very careful about saying "brain research proves." As a matter of fact, brain research does not prove much for educators. The neuroscientists are not doing research for us, unfortunately.

They are not teachers. And if you have ever been to a neuroscience conference and watched one of them, you know they do not know much about teaching. They are doing a tremendous amount of research, trying to understand this very complex three pounds that is floating around up in our skulls. And most of the neuroscientists work in a very, very narrow field and they often do not communicate with other neuroscientists.

My belief is that it is going to be up to us, as the educators who understand teaching and learning, who are in the real laboratory, called the classroom, to take this research and interpret it and translate it for our own use. But you cannot go out and say, after you have been to this presentation today, well, brain research proves this about adolescents or brain research proves that. It is beginning to give us an increased understanding, and the better we understand the adolescent brain, or any brain, the better we are going to be able to educate it.

What I would like you to do to start with is just talk to the person next to you for just 30 seconds and see if you can list the characteristics of the typical adolescent.

[Pause]

PAT WOLFE: Now, tell me some of the things you just listed. Just kind of call them out. What is one thing that characterizes it?

AUDIENCE MEMBER: Moody.

PAT WOLFE: Moody, big mood swings. Giving you a hug one day, kicking you in the shins the next. Okay, what else?

AUDIENCE MEMBER: Hormonal.

PAT WOLFE: Hormonal, okay. And we are going to talk about this a little bit, because we have felt, up until recently, that most of these characteristics are hormonal, and what we are finding out is that a lot of it is above the neck. What else?

AUDIENCE MEMBER: Fearless.

PAT WOLFE: Fearless. In other words, real risk-takers, without thinking about the consequences of their actions. What else?

AUDIENCE MEMBER: Social.

PAT WOLFE: Social. Some are social sometimes, and then moody and do not want to talk to anyone. And this is social with their peers, not their parents. What else?

AUDIENCE MEMBER: Fidgety.

PAT WOLFE: Fidgety, fidgety. You bet. Lots of movement. You listed them all. Behavior is characterized by swings of mood, risk taking. How about poor judgment? Disorganization. Do I do my homework first or do I play a videogame first? Disrespect for authority. You have reached a point where you know nothing. And little emotional control. What is it? What is going on?

The conventional wisdom, and it was mentioned, was hormonal. Now, I taught middle school for a very short time. And then I moved to kindergarten. The reason is it was like teaching hormones in Nikes. The conventional wisdom has been this, that up until -- well, we have to back up here. Let's talk a little bit just about how a brain develops and then we can understand this.

The brain is the only organ in the body that sculpts itself through its experience with the world. That is a powerful statement, if you think about it. You don't change your spleen by your inner changes with your environment, or your liver. Well, you could really mess up your liver, I guess, by drinking too much. But you actually change your brain minute by minute, day by day, year by year, by what you do with it. Now, there are some genetic influences, and this is what we want to talk about here.

When a baby is born, the baby's brain is about one pound, but it already has 100 billion neurons. And that 100 billion neurons, for all practical purposes, with a few exceptions, will be the same 100 billion neurons you have when you die. Learning and brain growth is not a matter of growing more brain cells. Now, within the last few years, they have discovered that the adult brain does grow a few brain cells in a couple of parts of the brain. But, for the most part, the brain cells you have when you are born have to last you the rest of your life.

So that the nine months the baby's brain is developing in the womb is an extremely critical and very important time, because the baby has to grow a full set of neurons. And the process by which these neurons develop is called neurogenesis, "neuro" meaning mind, "genesis" meaning beginning. At the rate of about 250,000 neurons a minute, the baby begins to build a brain from the moment of conception. By about 28 weeks, or 7 months, in utero, the baby's brain has overdone its job and over-proliferated twice as many neurons as it will need when it is born.

So, in the last two months of fetal development, genetically programmed cell death takes place. It has a name. It is called apoptosis. And what apoptosis means is that it is genetically programmed. This happens in every baby's brain, with normal development. The brain prunes away half of the neurons that it has developed. So, in the last two months before you were born, you lost half your brain cells. And that is a normal process. And then, basically, you do not lose any more brain cells, unless you are unfortunate enough to have some neurological disease like Alzheimer's. So, those cells are there.

Now, the question that would come up and so I will just answer it now is, what about premature babies? It is very interesting that that program, that genetic program, lasts for nine months regardless of when the baby is born. So, if you have a child that is born prematurely at seven months, that programmed cell death, that pruning away of all those excess neurons, continues to nine months. So, you should always measure a premature child's development not from the day it was born but from the day it was due. And then, quite often, unless drugs or alcohol were involved, brain development is pretty much normal in that child.

So, this is a program that lets you build all your brain cells before you are born. Now, these neurons, these brain cells, make up about 10 percent of your brain and, for the most part, they do not regenerate. Now, the rest of your body does.

If you look at these skin cells in the back of your hand, what do you know about them? You have six pounds of skin. Once a month, it is new. You get a complete new layer of skin every month. Unfortunately, it comes back just like it was. But it is a new layer.

Now, the stomach lining is new every four days, because the acids that you need to digest your food do not distinguish between the food and the lining of the stomach and it just digests the lining of the stomach, too, so it must continually regenerate. But neurons do not do that. Why not? Because neurons are the basic functional unit of the brain and they talk to each other. And that talking to each other is, as you will see in a little bit, is what we call learning. They make connections, and your memory is stored at the synapse.

So, what would happen if you got new brain cells once a month? You would wake up every 28 days and you would not know who you were. And you could not ask anyone, because they would not know either. A friend of mine says you could hide your own Easter eggs.

[Laughter]

So, we have a genetic setup here where, in neurogenesis, you are going to grow all your brain cells, basically, before you are born. Now, the other cells in the brain, which make up 90 percent of the brain, are called glial cells, and they do reproduce. And we are going to look at glial cells in a minute, because this is one of the big changes that is occurring in the adolescent brain. But, basically, what glial cells are is they are the nursemaid cells. They make up the blood-brain barrier. They wrap themselves around axons in a substance called myelin. They carry away waste material from the brain. They make up 90 percent of your brain. You have 10 times as many glial cells as you have neurons, and they do regenerate.

And, interestingly enough, many of the glial cells regenerate in response to how many connections you are growing in the brain on your neurons. So, the more you use your brain, the more glial cells you will have. Ray and Diamond found that Einstein had more glial cells than the average, but he had the same number of neurons in a selected portion of tissue.

So, now we have a baby that is born. The brain is about one pound. It is very small. Within the first year, it doubles in weight and size. By age four or five, the brain is 95 to 96 percent of its adult size. The other 4 to 5 percent will occur between age five or six and adolescence. By adolescence, you have a full-sized brain. Notice, I did not say you have an adult brain.

Now, I have to back up just again here for a minute. Around age two -- no, let's go back even earlier. Even before you are born, your brain starts making connections between brain cells. You do not get more neurons. What is all that growth? That growth, from one pound to three pounds in four years, is a growth of connections, a growth of glial cells, and a growth of myelin. That is what makes the brain get bigger.

The connections between brain cells, between what we call dendrites and axon branches, is learning. Learning is a matter of making connections. So, when you learn something, when a child learns that you call this a chair or you call this a table, that is making literal connections in the brain. So, learning is a matter of making connections. Well, what happens is you start making connections before you are born. The brain starts learning before you are born. Babies are born recognizing their mother's voice, their mother's smell, music they heard before they were born. They have already started.

You can take identical twins, which is as close as we have to a cloned person, and before they are born they are different, depending on their placement in the womb. You have more left-handed identical twins than you do in the normal population because the right hand may have been up against the other twin and you couldn't use it but you could use this one. And the brain says, okay, this is getting a lot of action, so I will become left-handed. So, we have both genes and environment.

Now, these connections start and, oh, my, do they grow, with trillions and trillions of connections in the first two years. By age two, we have a problem. We have too many connections now. Now, before they were born they had too many cells, so we pruned them away. Well, if you have got to many connections, what are we going to need to do? Prune them away. This massive buildup of connections causes this blooming confusion in the two-year-old's brain. What do we call it?

AUDIENCE RESPONSE: The terrible twos.

PAT WOLFE: The terrible twos.

Now, if I ask you to characterize the behavior of a terrible two, what would it equate to?

AUDIENCE RESPONSE: Adolescence.

PAT WOLFE: Adolescence. And that is a really important point.

So, what are the characteristics? Erratic behavior. The two-year-old is on your lap cuddling one minute and screaming, no, you cannot make me the next. Fortunately, we all live through it. Because what happens is this pruning, just like the pruning of excess cells before the baby was born, the pruning of excess connections at age two allows a more refined, more efficient brain. And around three, we get ourselves a relatively nice little kid again.

The conventional wisdom was that that only happens at two, and that by the time the child is an adolescent, they have got a full-sized adult brain and that then they must be adults. The conventional wisdom has been overturned. Because what they have discovered is we have a very similar process happening in the adolescent brain that was happening in this two-year-old brain.

Now, here is a picture of the two-year-old brain. This is a piece of cortex. This is at birth and this is age two. This is from Marianne Diamond's work. And this shows you the tremendous number of connections. Now, obviously this is not the same slide or you wouldn't have it. Do you know what I mean? So, you have the same number of neurons here as you have here. Brain growth and development is not growing more neurons; it is growing more of these connections. Now, if I had one of these at three, you would not see this many connections.

So, do not get the idea that the more connections a brain makes, the better off you are. Not necessarily. Because as you learn things you make connections. But then as you get older and you begin to have more experience with the world, you say, well, that is not true, or this piece of information fits better in this network. So, learning is a matter of growing and pruning away and refining as this continuous dynamic process is taking place.

Now, we have to do a biology moment, so close the doors. And I know some of you know this, but in order to understand the changes that are taking place in the brain, we have to do just a little bit of biology. So, here is our brain. And I suspect that most of you know is weighs about how much?

AUDIENCE RESPONSE: Three pounds.

PAT WOLFE: Three pounds. And it is covered with a very thin layer, about a quarter of an inch thick, which is called the...?

AUDIENCE RESPONSE: Cortex.

PAT WOLFE: Cortex. And in Latin cortex means?

AUDIENCE RESPONSE: Bark.

PAT WOLFE: Bark. So, just like a tree is covered with bark, your brain is covered with this very thin layer called the cortex. And it covers both hemispheres, and it is deeply folded so it will fit inside a skull, and it grows. And this is the part of the brain that you influence the most in a classroom. There are other structures in the brain that we will look at a little bit later that highly influence learning, but they do not change as you learn. This does. This changes tremendously, this cortex.

You also know you have two hemispheres, a right hemisphere and a left hemisphere. And through brain imaging techniques in the last 30 years or so, we have discovered what different parts of the cortex control. That you have a modular brain so to speak. And that the back part of your brain, clear back here of the cortex, called the visual cortex or the occipital lobes, is the part of the brain that allows you to take individual stimuli, turn it into an electrical impulse and send it up to the cortex so you are aware of what you are seeing.

The sides of the brain, the temporal lobes, often called the auditory cortex, takes in the auditory stimuli. Again, it changes it into electrical impulses and allows you to be aware of what you are hearing. Parietal lobes, kind of a flat, plate-like part up here, integrates sensory data. It lets you know where you are in space. It appears to have some impact on your calculating abilities, mathematics, et cetera.

And then there are these huge, huge frontal lobes. And the frontal lobes are the seat of human cognition and consciousness, whatever that is. This is the part of the brain that allows you to be aware of what you are thinking, to be conscious, so to speak. And this is what probably separates us from the animals. While animals have emotions, we do not have any evidence that they are consciously aware of what they are thinking at the moment or that they are aware of what we call our feelings -- "I am angry. I am happy. I am sad." They have the emotion, but not the conscious awareness of it.

In a dog's brain, you have frontal lobes and you have a motor cortex and you have parietal lobes and temporal lobes, but the way the cortex is designated is different. A large part of a dog's brain is designated for smell because, for their survival, they have to sniff their way. Have any of you tried to take a dog for a power walk and they go for a power sniff? Yes, okay.

A rat's brain is the same thing. A large part of it is designated for smell. A bat's brain, a large part of it would be designated for what? For hearing.

But we have these huge frontal lobes, often called the undesignated cortex. And what we have been able to use this for over time is to develop this absolutely fantastic ability to communicate with one another, to develop a language, to come up with a theory of quantum physics, to design and build a cathedral, to compose symphonies. This is what makes us uniquely human. These frontal lobes are going to be very, very important in just a minute.

Now, this is just some basic information, because we are going to talk about frontal lobes in a minute. And you need to know that these huge lobes right here behind your forehead are the part of the brain that allows you to take in what I am saying this morning, hook it to information you already know, and agree or disagree with it. This is what allows you to be uniquely human.

A second piece of biology. Here is a neuron. And I want to talk about a part of the neuron that is not talked about a lot. I think most of you know that dendrites are the part of the cell that receives information from another cell and then axon branches communicate with other cells at what we call the synapse. But I want to draw your attention to this long stringy branch right here on the neuron. There is only one of them and it is called an axon. And the axon is a sender of information. Now, when a cell receives information, it is chemical information which it translates into an electrical impulse.

This is a cell. It starts at the bottom of a cell and sends an electrical impulse down the axon out to all the ends of the axon branches, which allows it to communicate. Now, the average cell neuron in your brain has 6,000 dendrites. It can receive information from 6,000 other cells and it can send information out to 6,000 other cells. This is the basic communication unit of the brain. Everything you do, all human behavior, at its base are these neurons talking to one another.

You have got this funny substance here. And starting around birth -- actually, in some cells, before birth -- neurons get this coating on them. And it is actually a type of glial cell that wraps itself around the axon. It is a fatty, waxy substance. Now, you tell me, why would anyone want a fatty, waxy substance wrapped around their axons anyway? What would that do?

AUDIENCE RESPONSE: Protection.

PAT WOLFE: Some protection, but more insulation.

Now, the electrical impulses going down the axon is not like the electricity over here in the wall. It is actually called an action potential, and it is a change in polarization from positive to negative, which starts up a little impulse and it goes down the axon. Well, before a neuron is myelinated, it is called immature. So, tell me, what neurons in a baby do you think are already myelinated at birth or the baby could not survive? The sucking reflex.

But tell me what the arms and hands of newborn look like. What do they do? They flail, don't they? The baby does not have any control of them. So, you know that the neurons in the brain that control motor movement in the arms and legs are not myelinated yet.

Now, take a colt born out here in the field today. What could that colt do almost immediately?

AUDIENCE RESPONSE: Stand up and walk.

PAT WOLFE: Stand up and walk. So, what do you know about the colt's neurons that control movement of the legs?

AUDIENCE RESPONSE: They're myelinated.

PAT WOLFE: They are already myelinated. When do humans' neurons for control of motor movement in the legs get myelinated?

AUDIENCE RESPONSE: About a year.

PAT WOLFE: About a year. Somewhere between nine months and 18 months.

So, do you see what myelin does? It allows the electrical impulse to travel more efficiently. It insulates it, so to speak. And myelin is something else we are going to talk about. It appears in a preset pattern. This appears to be genetic. You do not influence the development of myelin a lot by experience. The only way you could effect that is -- well, when a baby is ready to walk, the baby walks.

The neurons are myelinated and the child gets up and starts walking. I guess if you kept them from walking, then you could influence the development. But normally myelin is just going to develop when it is ready to develop and you cannot push it. There is not any experience you can give a person to say, I am going to make your neurons -- or I am going to take this baby and I am going to practice walking at three months and I am going to get the myelin growing faster. You cannot do that.

Now, have you ever heard the terms gray matter and white matter? You've heard that. Let me tell you what gray matter and white matter are. What we have here is a cross-section through the human brain, top to bottom. And you can see the cortex as clear as a bell. Do you see the cortex here, how it is going in and out of all of these folds? That is that quarter-inch-thick layer. And it is packed with six layers of neurons, very tightly packed, and they look gray. And that is called the gray matter. So, you can see the gray matter.

And then, do you see all of this white in here? These are neurons that are traveling between the cortex and other parts of the brain and they are covered with myelin, and myelin is white. So, that is the white matter of the brain. Have you got that much? Because we are about ready to start in the changes in the adolescent brain, but before we can do that, you have to turn to the person next to you and one of you needs to explain what the different lobes are and what the cortex does. And the other person needs to explains what myelin is. And we are going to change your connections right here and reinforce them by having you do that. You have two minutes.

[Pause]

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