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The Associated Press reports that Hong Kong researcher Li-Hai Tan has found that dyslexia affects different parts of the brain depending on whether they are raised reading English or Chinese.
Published in the Proceedings of the National Academy of Sciences, the findings mean 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 or Chinese,” says Tan. “Our finding yields neurobiological clues to the cause of dyslexia.”
Reading an alphabetic language like English (which represents individual sounds with symbols) requires different skills than reading Chinese (which uses symbols to represent whole words).
Past studies have suggested that the brain may use different networks of neurons in different languages, but none had indicated a difference in the structural parts of the brain involved.
Tan’s group studied the brains of students raised reading Chinese, using fMRI imaging. They then compared those findings with similar studies of the brains of students raised reading English.
The process of becoming a skilled reader changes the brain, says Guinevere Eden, director of the Center for the Study of Learning at Georgetown University, who was not part of Tan’s team. “Becoming a reader is a fairly dramatic process for the brain,” she notes.
Learning to read is culturally important, but it is not “natural,” says Eden. Brains cope with different writing systems differently.
For example, English-speaking children learn the sounds of letters and how to combine them into words. Chinese children memorize by writing thousands of symbols which represent whole words. Eden explains, “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.
And that means we “can’t just assume that any dyslexic child is going to be helped by the same kind of intervention.”
The new finding suggests that treating Chinese speakers with dyslexia may involve using working memory tasks and tests relating to sensor-motor skills. On the other hand, treatment of dyslexic English readers who are struggling involves focusing on sound awareness and letter-sound conversions.
According to Tan, the underlying cause of brain structure abnormalities in dyslexia is currently unknown.
“Previous genetic studies suggest that malfformations of brain development are associated with mutations of several genes and that developmental dyslexia has a genetic basis,” Tan wrote via email to Randolph Schmid of the Associated Press.
“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.”
In their paper the researchers note that imaging studies of the brains of dyslexic children using alphabetic languages like English have identified unusual function and structure in areas different from those of Chinese readers.
English Dyslexia Involves Disruption in:
- left temporoparietal 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).
Chinese Dyslexia Involves disruption In:
- 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.
Interestingly, the article also reports that a separate paper, published two years ago by the University of Michigan, reported that Asians and North Americans see the world differently.
When North American students of European background were shown a photograph, they paid attention to the object in the foreground of a scene.
Students from China spent more time studying the background, taking in the whole scene, and interpreted the foreground action in terms of the whole picture.
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