Developmental dyslexia is characterized by a severe reading problem in people who have normal intelligence and schooling. Impaired reading of alphabetic scripts is associated with dysfunction of left temporoparietal brain regions. These regions perform phonemic analysis and conversion of written symbols to phonological units of speech (grapheme-to-phoneme conversion); two central cognitive processes that mediate reading acquisition. Furthermore, it has been assumed that, in contrast to cultural diversities, dyslexia in different languages has a universal biological origin. Here we show using functional magnetic resonance imaging with reading-impaired Chinese children and associated controls, that functional disruption of the left middle frontal gyrus is associated with impaired reading of the Chinese language (a logographic rather than alphabetic writing system). Reading impairment in Chinese is manifested by two deficits: one relating to the conversion of graphic form (orthography) to syllable, and the other concerning orthography-to-semantics mapping. Both of these processes are critically mediated by the left middle frontal gyrus, which functions as a centre for fluent Chinese reading that coordinates and integrates various information about written characters in verbal and spatial working memory. This finding provides an insight into the fundamental pathophysiology of dyslexia by suggesting that rather than having a universal origin, the biological abnormality of impaired reading is dependent on culture.

Language development entails four fundamental and interactive abilities: listening, speaking, reading, and writing. Over the past four decades, a large body of evidence has indicated that reading acquisition is strongly associated with a child's listening skills, particularly the child's sensitivity to phonological structures of spoken language. Furthermore, it has been hypothesized that the close relationship between reading and listening is manifested universally across languages and that behavioral remediation using strategies addressing phonological awareness alleviates reading difficulties in dyslexics. The prevailing view of the central role of phonological awareness in reading development is largely based on studies using Western (alphabetic) languages, which are based on phonology. The Chinese language provides a unique medium for testing this notion, because logographic characters in Chinese are based on meaning rather than phonology. Here we show that the ability to read Chinese is strongly related to a child's writing skills and that the relationship between phonological awareness and Chinese reading is much weaker than that in reports regarding alphabetic languages. We propose that the role of logograph writing in reading development is mediated by two possibly interacting mechanisms. The first is orthographic awareness, which facilitates the development of coherent, effective links among visual symbols, phonology, and semantics; the second involves the establishment of motor programs that lead to the formation of long-term motor memories of Chinese characters. These findings yield a unique insight into how cognitive systems responsible for reading development and reading disability interact, and they challenge the prominent phonological awareness view.dyslexia ͉ phonological awareness ͉ reading development ͉ child language ͉ reading Chinese

In functional neuroimaging studies, individuals with dyslexia frequently exhibit both hypoactivation, often in the left parietotemporal cortex, and hyperactivation, often in the left inferior frontal cortex, but there has been no evidence to suggest how to interpret the differential relations of hypoactivation and hyperactivation to dyslexia. To address this question, we measured brain activation by functional MRI during visual word rhyme judgment compared with visual cross-hair fixation rest, and we measured gray matter morphology by voxel-based morphometry in dyslexic adolescents in comparison with (i) an age-matched group, and (ii) a readingmatched group younger than the dyslexic group but equal to the dyslexic group in reading performance. Relative to the agematched group (n ‫؍‬ 19; mean 14.4 years), the dyslexic group (n ‫؍‬ 19; mean 14.4 years) exhibited hypoactivation in left parietal and bilateral fusiform cortices and hyperactivation in left inferior and middle frontal gyri, caudate, and thalamus. Relative to the readingmatched group (n ‫؍‬ 12; mean 9.8 years), the dyslexic group (n ‫؍‬ 12; mean 14.5 years) also exhibited hypoactivation in left parietal and fusiform regions but equal activation in all four areas that had exhibited hyperactivation relative to age-matched controls as well. In regions that exhibited atypical activation in the dyslexic group, only the left parietal region exhibited reduced gray matter volume relative to both control groups. Thus, areas of hyperactivation in dyslexia reflected processes related to the level of current reading ability independent of dyslexia. In contrast, areas of hypoactivation in dyslexia reflected functional atypicalities related to dyslexia itself, independent of current reading ability, and related to atypical brain morphology in dyslexia.inferior frontal region ͉ inferior parietal lobule ͉ voxel-based morphometry ͉ functional MRI ͉ compensation D yslexia is a developmental condition characterized by low reading achievement in people who otherwise have cognitive abilities, motivation, and education necessary for accurate and fluent reading (1). Dyslexia, estimated to affect 5-17% of children and 80% of all individuals with a learning disability (2, 3), is characterized by inaccurate and/or slow, effortful reading that typically originates with weakness in the phonological processing of language (4-8).The brain basis of dyslexia has been examined by functional and structural neuroimaging. Functional imaging studies regularly report hypoactivation in dyslexia, especially in the left parietotemporal region, which may support the mapping of phonology onto orthography, and in the left fusiform region, which may support skilled orthographic decoding (9-12). Hyperactivation in dyslexia has also been observed, most frequently in left inferior frontal gyrus (IFG) (13)(14)(15)(16)(17)(18)(19). Hyperactivation in left IFG, a region associated with articulation and naming (20), may reflect compensatory processes engaged by dyslexic individuals attempting to overcome...