http://dsc.discovery.com/news/2008/04/08/dyslexia-language.html
Dyslexia Differs by Language
Randolph E. Schmid, Associated Press
Different Language, Different Dyslexia
April 8, 2008 -- Dyslexia affects different parts of children's brains
depending on whether they are raised reading English or Chinese. That
finding, reported in Monday's online edition of Proceedings of the
National Academy of Sciences, means that therapists may need to seek
different methods of assisting dyslexic children from different cultures.
"This finding was very surprising to us. We had not ever thought that
dyslexics' brains are different for children who read in English and
Chinese," said lead author Li-Hai Tan, a professor of linguistics and
brain and cognitive sciences at the University of Hong Kong. "Our
finding yields neurobiological clues to the cause of dyslexia."
Millions of children worldwide are affected by dyslexia, a
language-based learning disability that can include problems in reading,
spelling, writing and pronouncing words. The International Dyslexia
Association says there is no consensus on the exact number because not
all children are screened, but estimates range from 8 percent to 15
percent of students.
Reading an alphabetic language like English requires different skills
than reading Chinese, which relies less on sound representation, instead
using symbols to represent words.
Past studies have suggested that the brain may use different networks of
neurons in different languages, but none has suggested a difference in
the structural parts of the brain involved, Tan explained.
Tan's research group studied the brains of students raised reading
Chinese, using functional magnetic resonance imaging. They then compared
those findings with similar studies of the brains of students raised
reading English.
Guinevere F. Eden, director of the Center for the Study of Learning at
Georgetown University in Washington, said the process of becoming a
skilled reader changes the brain.
"Becoming a reader is a fairly dramatic process for the brain,"
explained Eden, who was not part of Tan's research team on this paper.
For children, learning to read is culturally important but is not really
natural, Eden said, so when the brain orients toward a different writing
system it copes with it differently.
For example, English-speaking children learn the sounds of letters and
how to combine them into words, while Chinese youngsters memorize
hundreds of symbols which represent words.
"The implication here is that when we see a reading disability, we see
it in different parts of the brain depending on the writing system that
the child is born into," Eden said.
That means, "we cannot just assume that any dyslexic child is going to
be helped by the same kind of intervention," she said in a telephone
interview.
Tan said the new findings suggest that treating Chinese speakers with
dyslexia may use working memory tasks and tests relating to sensor-motor
skills, while current treatments of English dyslexia focus on
letter-sound conversions and sound awareness.
He said the underlying cause of brain structure abnormalities in
dyslexia is currently unknown.
"Previous genetic studies suggest that malformations of brain
development are associated with mutations of several genes and that
developmental dyslexia has a genetic basis," he said in an interview via
e-mail.
"We speculate that different genes may be involved in dyslexia in
Chinese and English readers. In this respect, our brain-mapping findings
can assist in the search for candidate genes that cause dyslexia," Tan said.
In their paper, the researchers noted that imaging studies of the brains
of dyslexic children using alphabetic languages like English have
identified unusual function and structure in the left temporo-parietal
areas, thought to be involved in letter-to-sound conversions in reading;
left middle-superior temporal cortex, thought to be involved in speech
sound analysis, and the left inferior temporo-occipital gyrus, which may
function as a quick word-form recognition system.
When they performed similar imaging studies on dyslexic Chinese
youngsters, on the other hand, they found disruption in a different
area, the left middle frontal gyrus region.
The study was funded by the Ministry of Science and Technology of China,
the Hong Kong Research Grants Council and the University of Hong Kong.
In a separate paper, published two years ago, University of Michigan
researchers reported that Asians and North Americans see the world
differently.
Shown a photograph, North American students of European background paid
more attention to the object in the foreground of a scene, while
students from China spent more time studying the background and taking
in the whole scene.
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