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Your teenage brain: adolescence can be a turbulent time. Find out why it's largely your' brain's fault.


The teen years are filled with visible changes. You are growing faster than you can measure. But why are you suddenly more impulsive and quick to squabble with your parents? You can blame your teen brain.

Over the past decade, researchers have been exploring both the structure and function of teenagers' brains Using magnetic resonance imaging (MRI) machines, which take pictures of the brain, and electroencephalograms, (EEGs) which measure electrical activity, scientists are revealing that your brain is a work in progress. "A teen brain is not an adult brain with fewer miles on it. It's something very different, and it still has a long way to go," says Frances Jensen, a neurologist (doctor who studies the brain) at Children's Hospital Boston.


By the time you turn 6 years old, your brain reaches 90 percent of its final adult volume. Because it appeared that the brain had little growing left to do, neurologists assumed that it was fully formed by then. But researchers at the National Institute of Mental Health have shown that that's not the case.

Using an MRI machine, they scan a group of people ages 3 to 30 every two years to see how the brain changes as we grow and acquire new skills and experiences. Since 1991, they have obtained more than 6,000 scans from 2,000 people. They found that the amount of gray matter, or wrinkly outer layer of brain tissue that processes and stores information, peaks at around age 12. This large volume of gray matter means that your brain is actively learning throughout childhood. It continues to do so through adolescence, but as the kids in the study got older, connections between neurons in the brain, or synapses, became more refined. The stronger synapses are reinforced, and unnecessary ones are cut in a process called synaptic pruning (see Nuts & Bolts, p. 24). "It's a very busy time. The brain is forming new connections, getting rid of connections that aren't used, and strengthening ones that are used," says Jay Giedd, who led the research team.


While Giedd's team found structural brain changes caused by synaptic pruning by studying images of the brain, researchers Irwin Feinberg and Ian Campbell at the University of California, Davis, found evidence of synaptic pruning by studying the electrical activity of the brain during sleep.

Over a period of eight years, Campbell and Feinberg monitored the brain activity of children while they slept. They recorded EEGs that show slow, regular waves, called delta waves, during the deepest parts of the sleep cycle. This stage of sleep is thought to be a restorative stage, when your brain recovers from all the work it did during the day.

In children ages 11 to 16.5, there was a sharp drop in delta waves. "We think this decline is driven by synaptic pruning," says Campbell. The decrease in delta waves observed while teens sleep could be caused by a reduction in the size of groups of brain cells that "talk" to one another. And that indicates a drop in the amount of work that the brain is doing during the day.


As the gray matter's synapses are being trimmed at night, there is another process going on with your brain's white matter. White matter is the connective tissue that links the different areas of your brain. It is white because of a fatty substance called myelin, which insulates nerve cells to help speed up connections.

White matter doesn't form in every part of the brain at the same time. "The process of connecting the parts of the brain together happens from the back of your brain to the front," explains Jensen. By the time the teen years hit, the white matter has already made a lot of important connections in your brain, such as the ones that allow you to remember the vocabulary for your Spanish quiz next week or the motor skills to slam dunk a basketball at Friday's game.

The final part of the brain to connect up is the prefrontal cortex. This is the area that governs insight, judgment, planning, the interpretation of social cues, and the ability to curb your impulses.


While your prefrontal cortex is maturing, you are more susceptible to some typical teen behaviors, like taking risks--both good and bad. Since your brain is still learning at a high rate, and still making many connections every day, you can use this unique time to shape your developing brain. Teens are at an optimal age to learn new skills and practice those they want to improve.


How can you safely tap into your teen brain's tendency to want to try new things? "Be in a play or join a soccer team," says Wilkie Wilson, the director of the new DukeLEARN program, which strives to educate teens about these changes that are happening in their brains. "You can do things that will optimize the way your brain functions and be better at almost anything you want to be better at, whether it's academics, athletics, or social interactions," says Wilson.

video extra

Watch animations of Giedd's MRI data showing the changes in the teen brain at: scienceworld

nuts & bolts


By age 11 for girls and 12 for boys, your neurons have formed thousands of new connections (left). Over the next several years, regularly-used connections will be strengthened, while those that aren't used will be trimmed away, like snipping off stray threads with scissors (right).



Your Teenage Brain


* An adult human's brain has about 100 billion neurons and makes up only about 3 percent of his of her total body weight, but it gobbles up one sixth of the energy the body needs each day.


* In the article, you learned that there is still time to train your brain in a new activity. What sports, hobbies, or skills would you like to try out of improve? Why?


PHYSICAL EDUCATION: What are some ways you could train your brain and become a better athlete? Split the class into groups. Have them pick a sport and identify the key skills involved in each sport. Then, devise a training program that will highlight each of these skills, and present it to the class.


* Want to know more about your brain? Check out this illustrated guide to the human brain: The Great Brain Book: An Inside Look at the Inside of Your Head by HP Newquist, Scholastic Reference, 2005.

DIRECTIONS: Match the words in the left column with the word or phrase in the right column.
-- 1. gray matter         a. white, fatty substance that insulates
                             nerve cells
-- 2. white matter        b. slow, regular waves that occur during the
                             deepest part of the sleep cycle
-- 3. synapses            c. area of the brain that governs insight,
                             judgment, planning, and the interpretation
                             of social cues
-- 4. myelin              d. connective tissue that links the different
                             areas of the brain
-- 5. prefrontal cortex   e. wrinkly outer layer of brain tissue that
                             processes and stores information
-- 6. delta waves         f. connections between neurons in the brain

Your Teenage Brain

1. e 2. d 3. f 4. a 5. c 6. b
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Title Annotation:LIFE: HUMAN BRAIN
Author:Hamalainen, Karina
Publication:Science World
Geographic Code:1USA
Date:Nov 9, 2009
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