How the Brain Strings Words Into Sentences

ScienceDaily (Nov. 28, 2011) — Distinct neural pathways are important for different aspects of language processing, researchers have discovered, studying patients with language impairments caused by neurodegenerative diseases.


While it has long been recognized that certain areas in the brain's left hemisphere enable us to understand and produce language, scientists are still figuring out exactly how those areas divvy up the highly complex processes necessary to comprehend and produce language.

Advances in brain imaging made within the last 10 years have revealed that highly complex cognitive tasks such as language processing rely not only on particular regions of the cerebral cortex, but also on the white matter fiber pathways that connect them.

"With this new technology, scientists started to realize that in the language network, there are a lot more connecting pathways than we originally thought," said Stephen Wilson, who recently joined the University of Arizona's department of speech, language and hearing sciences as an assistant professor. "They are likely to have different functions because the brain is not just a homogeneous conglomerate of cells, but there hasn't been a lot of evidence as to what kind of information is carried on the different pathways."

Working in collaboration with his colleagues at the UA, the department of neurology at the University of California, San Francisco and the Scientific Institute and University Hospital San Raffaele in Milan, Italy, Wilson discovered that not only are the connecting pathways important for language processing, but they specialize in different tasks.

Two brain areas called Broca's region and Wernicke's region serve as the main computing hubs underlying language processing, with dense bundles of nerve fibers linking the two, much like fiber optic cables connecting computer servers. But while it was known that Broca's and Wernicke's region are connected by upper and a lower white matter pathways, most research had focused on the nerve cells clustered inside the two language-processing regions themselves.

Working with patients suffering from language impairments because of a variety of neurodegenerative diseases, Wilsons' team used brain imaging and language tests to disentangle the roles played by the two pathways. Their findings are published in a recent issue of the scientific journal Neuron.
"If you have damage to the lower pathway, you have damage to the lexicon and semantics," Wilson said. "You forget the name of things, you forget the meaning of words. But surprisingly, you're extremely good at constructing sentences."

"With damage to the upper pathway, the opposite is true; patients name things quite well, they know the words, they can understand them, they can remember them, but when it comes to figuring out the meaning of a complex sentence, they are going to fail."

The study marks the first time it has been shown that upper and lower tracts play distinct functional roles in language processing, the authors write. Only the upper pathway plays a critical role in syntactic processing.
Wilson collected the data while he was a postdoctoral fellow working with patients with neurodegenerative diseases of varying severity, recruited through the Memory and Aging Center at UCSF. The study included 15 men and 12 women around the age of 66.

Unlike many other studies investigating acquired language disorders, which are called aphasias and usually caused by damage to the brain, Wilson's team had a unique opportunity to study patients with very specific and variable degrees of brain damage.

"Most aphasias are caused by strokes, and most of the strokes that affect language regions probably would affect both pathways," Wilson said. "In contrast, the patients with progressive aphasias who we worked with had very rare and very specific neurodegenerative diseases that selectively target different brain regions, allowing us to tease apart the contributions of the two pathways."

To find out which of the two nerve fiber bundles does what in language processing, the team combined magnetic resonance brain imaging technology to visualize damaged areas and language assessment tasks testing the participants' ability to comprehend and produce sentences.

"We would give the study participants a brief scenario and ask them to complete it with what comes naturally," Wilson said. "For example, if I said to you, 'A man was walking along the railway tracks. He didn't hear the train coming. What happened to the man?' Usually, you would say, 'He was hit by the train,' or something along those lines."

"But a patient with damage to the upper pathway might say something like 'train, man, hit.' We found that the lower pathway has a completely different function, which is in the meaning of single words."
To test for comprehension of the meaning of a sentence, the researchers presented the patient with a sentence like, "The girl who is pushing the boy is green," and then ask which of the two pictures depicted that scenario accurately.

"One picture would show a green girl pushing a boy, and the other would show a girl pushing a green boy," Wilson said. "The colors will be the same, the agents will be the same, and the action is the same. The only difference is, which actor does the color apply to?"

"Those who have only lower pathway damage do really well on this, which shows that damage to that pathway doesn't interfere with your ability to use the little function words or the functional endings on words to figure out the relationships between the words in a sentence."

Wilson said that most previous studies linking neurodegeneration of specific regions with cognitive deficits have focused on damage to gray matter, rather than the white matter that connects regions to one another.
"Our study shows that the deficits in the ability to process sentences are above and beyond anything that could be explained by gray matter loss alone," Wilson added. "It is the first study to show that damage to one major pathway more than then other major pathway is associated with a specific deficit in one aspect of language."

The study was primarily funded by grants from the National Institutes of Health and included the following co-authors: Sebastian Galantucci, Maria Carmela Tartaglia, Kindle Rising, Dianne Patterson (both at the UA's department of speech, language and hearing sciences), Maya Henry, Jennifer Ogar, Jessica DeLeon, Bruce Miller and Maria Luisa Gorno-Tempini.

Using magnetic resonance imaging of the brain, researchers can visualize the two main language processing regions, Broca's region (yellow) and Wernicke's region (purple). (Credit: Stephen Wilson)

Story Source:
The above story is reprinted from materials provided by University of Arizona. The original article was written by Daniel Stolte, University Communications.

Note: Materials may be edited for content and length. For further information, please contact the source cited above.

Journal Reference:

Stephen M. Wilson, Sebastiano Galantucci, Maria Carmela Tartaglia, Kindle Rising, Dianne K. Patterson, Maya L. Henry, Jennifer M. Ogar, Jessica DeLeon, Bruce L. Miller, Maria Luisa Gorno-Tempini. Syntactic Processing Depends on Dorsal Language Tracts. Neuron, 2011; 72 (2): 397 DOI: 10.1016/j.neuron.2011.09.014

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How To Help Your Child's Brain Grow Up Strong

September 14, 2011

Babies may look helpless, but as soon as they come into the world, they're able to do a number of important things. They can recognize faces and moving objects. They're attracted to language. And from very early on, they can differentiate their mother from other humans.
"They really come equipped to learn about the world in a way that wasn't appreciated until recently," says neuroscientist Sandra Aamodt. "It took scientists a long time to realize that their brains are doing some very complicated things."
Aamodt and fellow neuroscientist Sam Wang explain how the human brain develops from infancy to adolescence in their new book, Welcome to Your Child's Brain. The two researchers also offer tips for parents to help their children eat their spinach, learn their ABCs and navigate elementary school.

Before all of those things, however, children have to learn how to talk. Babies can differentiate syllables and new sounds from very early on, but there are ways for parents to help their children develop their language skills faster and more efficiently.
"The most simple way is to talk to your baby and around your baby a lot," says Aamodt. "And the other thing that parents can do is to respond when the baby speaks, even if the baby isn't forming the words correctly or you don't understand it. Just act like some communication has occurred — smile and give the baby a little pat — and that encourages the baby to continue to try to communicate."
But because language is so social, says Wang, passive exposure to words really doesn't help babies learn in any way.
"For instance, videos that are often shown to babies containing language are not nearly so effective," he says. "In some cases, people try to teach babies language by showing them videos in a foreign language. It doesn't work very well at all because these are not social ways of exposing a child to language."
Parents should also realize that their children may reach certain intellectual milestones at different times — and that's OK.
"Language is acquired quite well before the age of 6, but trying to force your children to read before the age of 4 is an effort that doesn't work very well because the brain is not very well-equipped to tell the letter 'b' from the letter 'd' and so on," says Wang. "[But] it's something that older children can do without any effort at all."
And children who grow up in bilingual households have a distinct advantage over their peers.
"Kids who learn two languages young are better able to learn abstract rules and to reverse rules that they've already learned," says Aamodt. "They're less likely to have difficulty choosing between conflicting possibilities when there are two possible responses that both present themselves. They're also better at figuring out what other people are thinking, which is probably because they have to figure out which language to use every time they talk to somebody in order to communicate."

Teaching Self-Control
Aamodt and Wang also emphasize the importance of teaching your children self-control from an early age.
"This is really critical because there are so many things parents want to do when they read parenting books," he says. "They take steps to teach their children math or reading ... but a big thing we can do for our children is to do the best to foster the development of self-control and willpower. Self-control and the ability to restrain impulses is associated with success at every age, whether it means being able to read at age 4, or being able to restrain impulses at a later age, or even what your peers think of you in high school. At all of these ages, willpower and self-control is a stronger predictor of academic success than IQ."

When children are young, they can learn self-control by focusing on any fun activity — whether that means studying martial arts or playing with dolls and planning a make-believe tea party.

"It gives the child practice at planning and organizing a series of topics to achieve a desired goal," says Aamodt. "When you're planning a tea party, you can't be acting like a fighter pilot. You have to be acting like a lady having a tea party. So pretending is one of the earliest types of exposure most kids get to planning and organizing their actions. And the more you practice that, the better you're going to be at it."
Making sure your child has fun while learning self-control is vitally important. Aamodt and Wang recommend, for instance, telling your child to pretend he or she is protecting a castle instead of just saying, "Stand still."
"Taking advantage of a child's natural sense of fun is a terrific way to instill these things," says Wang. "This is not the kind of thing that works well if it's forced. It can be something as easy as pretending to guard the castle or playing a take-turns game where you say, 'I'm going to draw an ear on this piece of paper, and when you see an ear, then it's your time to listen. And if you see a mouth on this other piece of paper, then it's your time to talk.' So all of these things can be done in very simple ways — in ways that are often fun — and the more fun it is, the more likely the child is to pay attention for a longer period of time. These things are fun, they don't cost money, and anybody can do it."
Dr. Sam Wang is an associate professor of neuroscience at Princeton University. Dr. Sandra Aamodt is a former editor-in-chief of Nature Neuroscience. They are also the co-authors of Welcome to Your Brain: Why You Lose Your Car Keys but Never Forget How to Drive and Other Puzzles of Everyday Life.

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Interview Highlights

On rewards vs. punishment

Dr. Aamodt: "With a child, you're not only concerned with getting a child to behave. You're also concerned with building a good relationship with your child. You want your child to think of you as a wonderful person to be around. You also don't want to teach our kids that the way we solve our interpersonal problems is with violence."
Dr. Wang: "Negative reinforcement is often not very effective with deterring behavior. ... negative reinforcement punishment tends to not be very general. So the child will avoid doing the specific thing that led to the punishment and not learn some broader rule. From a practical standpoint, negative reinforcement is not terribly effective."
On time out

Dr. Wang: "One thing that's similar between how children and nonhuman animals learn best is the phenomenon of timeout, which has entered the lexicon as a means of getting a child to avoid doing something later. It comes from technical literature from which the long phrase is 'timeout and reinforcement,' which is if the kid does something undesirable, you simply take the child, go to the corner, and just sit there. And you don't say anything at all. You don't have to be negative. You don't have to mete out a punishment. You just have to say, 'Sit there for 3 minutes, and when I come back, we're done.' And then you forget about it and move on. This works at all ages."
On stress and pregnancy

Dr. Aamodt: "Stress is not good for babies. No ethics review board in the world would approve [an experiment] in which we deliberately damaged [pregnant women's] babies. But there are these so-called experiments of nature. One experiment that was done looked at women who had been evacuated from a hurricane in Louisiana when they were pregnant. What that study found was a substantially increased rate of autism in babies who had been in their fifth or sixth month of gestation at the time they fled the hurricane. The effect was stronger in cases where the hurricane was more dangerous."
On 'tiger parenting'

Dr. Wang: "I'm not very much of a tiger mother. I'm more of a pussy cat dad."

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 Images retrieved from: http://catalog.fairbanksfoodbank.org/image/store/0/productImages/healthy_children.jpg

  Article retrieved from: http://www.npr.org/2011/09/14/140340903/how-to-help-your-childs-brain-grow-up-strong

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