Pictographic languages like Chinese and sound-based languages like English are processed differently in the brain. This might explain why dyslexia manifests differently in the brains of Chinese and English speakers.

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CHICAGO: Dyslexia may be a different brain disorder in English- and Chinese-speaking cultures, according to researchers who found different neurological deficits between the two.

English speakers with the reading disability typically have functional abnormalities and less grey matter in posterior parts of the brain associated with reading.

In Chinese dyslexics, on the other hand, the functional and structural brain abnormalities related to reading are in the left middle frontal region of the brain, new research reveals.

Published in the the U.S. journal Proceedings of the National Academy of Sciences, the findings are based on brain scans performed on 16 dyslexic Chinese speakers and 16 of their peers with normal reading ability.

Reading and the brain

Researchers first asked the 32 Beijing primary school students to look at two Chinese characters in different size font to see if they could identify the difference in size.

Having used this question to establish which parts of their brains were involved in reading, the investigators then presented the students with two more Chinese characters and asked them whether the two characters rhymed.

The second question was designed to test the students' phonological awareness, their sensitivity to the sound structure of language, which is considered an important and reliable predictor of reading ability.

The scans revealed that the students with the reading disability had less activity in the left middle frontal gyrus on the second task than the children without the disability. They also had less grey matter in this brain region than the children with normal reading skills.

Further, the Chinese dyslexic children did not have any abnormalities in the parts of the brain that have been shown to be problematic in alphabetic-language dyslexics.

Pictographic versus sound-based language

While surprising, the contrast can be explained by the fact that the Chinese language uses characters, while English uses a letter alphabet, one of the researchers said.

"At the functional level, it's easy to understand why Chinese and English speakers use different parts of the brain to read language," said Li-Hai Tan, a professor of linguistics and neuroscience at the University of Hong Kong, and author of the paper.

"The different brain networks accommodate the different features of English and Chinese. The two systems are dramatically different. Chinese is pictographic and English is more phonological, or sound-based."

However, he said that it was striking that the Chinese dyslexic children had less grey matter in the middle frontal gyrus. He said this was probably a function of genetics, since the characteristic is thought to be largely inherited.

This would suggest that the genetic makeup of Chinese-speaking dyslexics is different from that of English speakers with the same disorder since they have reductions of grey matter in different sites of the brain.

The study involved researchers from the University of Hong Kong, the Beijing Institute of Technology, and the University of Pittsburgh.