Plasticity of the Brain
What factors affect the brain’s plasticity, or ability to learn new things? How does the brain change with age? Neuroscientists have been addressing these questions since the early years of brain research.
During the first three years of life, the neurons in the brain rapidly form connections, or synapses, between each other. Neurons and synapses are overproduced in babies’ brains because their brains are taking in a lot of new information. At three years old, the brain begins to prune, or reduce the number of, these connections so that only the most used connections are intact. On average, three-year-olds have two times more synapses than adults have.
The brain does not lose all of its plasticity after the age of three. Even adults can learn a new skill, such as speaking a foreign language. Neuroscientists have found a second wave of brain growth and plasticity similar to that observed in infants, that begins just before puberty. During the teenage years, an intense period of pruning and strengthening begins and continues until the person is about 30. Connections that are used least are pruned away, and connections that are used the most are strengthened.
So how teenagers spend their time can affect their brain’s wiring. A teen violinist who stops practicing will see his or her musical skill fade. One researcher says, “If a teen is doing music or sports or academics, those are the cells and connections that will be hard-wired. If they’re lying on the couch or playing video games . . . those are the connections that are going to survive.”
Although researchers agree that playing video games affects the brain, they do not agree on how the brain is affected. Some studies suggest that video games could strengthen beneficial connections. Other studies imply that some beneficial connections could become weakened.
The Multitasking Brain
How might video games strengthen connections in your brain? Some video games present the player with complicated puzzles and patterns. The player must take in visual messages from the video screen while using problem-solving skills to analyze patterns. This multitasking requires the player to use different areas of the brain at the same time. Using language has a similar effect on the brain as playing video games in that both activate many areas of the brain at the same time.
For example, when you have a conversation with a friend, many areas of the brain become active. When you hear what your friend says, the brain area above your ear becomes active. When you form a response and speak, different brain areas become activated. The front of the brain is activated when you interpret your friend’s words and form a response. When you begin to respond, an area in the back of the brain becomes active. This area becomes more and more active as you talk.
Reading is another complicated activity. The same areas of your brain that are active when you talk to your friend are active when you read. But another area is also activated. This third area is farther back in the brain. It allows you to see and interpret the printed words in front of you. Even people who read Braille use the visual part of their brain to interpret what is on the page.
Every new discovery in neuroscience brings with it new questions. Some of these include the following:
- Can the plasticity of an adult brain be used to help adults recover from brain injuries and diseases?
- Can neuroscientists find ways to treat, or even cure, disorders such as Alzheimer’s disease?
- Why are humans, and not other primates, good at learning words and systems of grammar?
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Scanning the Brain
Much of today’s research on brain function uses functional magnetic resonance imaging (fMRI). In a traditional MRI, computers use information from a magnetic field to make a three-dimensional cross-sectional image of the brain. An fMRI uses an MRI machine to detect the areas of the brain that are receiving the most oxygenated blood. Computer software analyzes this data to determine which part of the brain is active while a person performs different tasks, such as reading, listening to music, doing math, or even receiving medical treatment.
MRIs and fMRIs, though, are expensive and cumbersome, making it impractical to do brain imaging studies on large groups of people. Some researchers are now experimenting with using portable, weak lasers to scan the brain. This technique is called functional near-infrared spectroscopy, or fNIRS. The weak lasers used in fNIRS can measure changes in blood flow in the front part of the brain. Because it is the size of a headband and easily portable, researchers have used fNIRS to study blood flow to the brain in extreme environments, such as in parabolic flight.
Late in 2010, scientists at the University of Texas in Dallas and Arlington presented a new invention that can take images of a brain without a person’s hair getting in the way: a laser hairbrush. Called “the hairbrush that reads your mind,” the “brush optrode” slides laser fibers between hair follicles, getting an
optical signal that is three to five times stronger than can be generated on the same head by a fNIRS headband.
Neuroscientist in Action
Dr. Rae Nishi
Title: Director, Neuroscience Graduate Program, University of Vermont
Education: Ph. D., Biology, University of California, San Diego
Dr. Rae Nishi’s research proves that you do not need complicated technology, such as fMRIs, to make discoveries in neuroscience. Through observation and experiment, Dr. Nishi’s research tries to answer the question: What causes brain cells to die?
Although the question is too broad to answer completely, Dr. Nishi has discovered a molecule that
seems to keep alive brain cells in dying chick embryos. She also found that by blocking a certain receptor on the surface of neurons, dying neurons will stop showing signs of decline. Studies of how and why brain cells might die are important in understanding Alzheimer’s and Parkinson’s diseases, which cause certain areas of the brain to become inactive.
“There is no profession as exciting as being a scientist,” Dr. Nishi says. “You get to learn new things
every day. You get to make discoveries. You get to solve puzzles.” Dr. Nishi is currently working to
determine how the molecules released during one neuron’s death might trigger the growth of new, neighboring neurons.