Cross-Language Differences

We have become increasingly interested in whether the neural network involved in language and reading is universal or language specific. The Chinese writing system is logosyllabic because each character corresponds to a syllable, whereas English is alphabetic because letters have a semi-regular mapping to individual sounds (i.e. phonemes). Despite these differences, our studies have shown that some brain regions are universally involved, but there are some interesting cross-language differences. In Chinese reading development, there are age-related decreases in speech related regions of the left hemisphere and increases in visual spatial regions of the right hemisphere, possibly reflecting a shift in reliance from phonological to visuo-orthographic representations over acquisition. In Chinese language development, there are decreases in the involvement of orthographic processing regions suggesting that written language has a reduced influence over spoken language processing. In contrast, the acquisition of an alphabetic writing system increasingly engages phonological processing regions during reading and fundamentally alters the network involved in phonological processing during spoken language processing. These cross-language differences are likely due to the more systematic mapping between orthography and phonology in English. We are just beginning to examine the neural basis of dyslexia in Chinese, and our results are consistent with a universal deficit in orthographic and phonological processing, but the nature and locus of the deficit appears to be different due to the unique structure of the writing system. We are also examining the hypothesis that Chinese children with dyslexia will have robust abnormalities in brain regions involved in semantic processing because a prominent part of the Chinese writing system is semantic radicals (i.e. parts of characters) that give clue to meaning. This would be consistent with our findings of greater involvement of semantic representations during reading acquisition in Chinese.