A structural–functional basis for dyslexia in the cortex of Chinese readers

Abstract

Developmental dyslexia is a neurobiologically based disorder that affects Ϸ5-17% of school children and is characterized by a severe impairment in reading skill acquisition. For readers of alphabetic (e.g., English) languages, recent neuroimaging studies have demonstrated that dyslexia is associated with weak reading-related activity in left temporoparietal and occipitotemporal regions, and this activity difference may reflect reductions in gray matter volume in these areas. Here, we find different structural and functional abnormalities in dyslexic readers of Chinese, a nonalphabetic language. Compared with normally developing controls, children with impaired reading in logographic Chinese exhibited reduced gray matter volume in a left middle frontal gyrus region previously shown to be important for Chinese reading and writing. Using functional MRI to study language-related activation of cortical regions in dyslexics, we found reduced activation in this same left middle frontal gyrus region in Chinese dyslexics versus controls, and there was a significant correlation between gray matter volume and activation in the language task in this same area. By contrast, Chinese dyslexics did not show functional or structural (i.e., volumetric gray matter) differences from normal subjects in the more posterior brain systems that have been shown to be abnormal in alphabetic-language dyslexics. The results suggest that the structural and functional basis for dyslexia varies between alphabetic and nonalphabetic languages.brain function ͉ Chinese language ͉ culture ͉ reading disorder ͉ neuroimaging D evelopmental dyslexia is characterized by unexpectedly low reading ability in people who have adequate intelligence, typical schooling, and sufficient sociocultural opportunities (1-10). Early investigations of postmortem dyslexic brains revealed structural abnormalities in both cortical and subcortical areas (11,12). Recent neuroimaging studies examining structurefunction relationships with alphabetic languages have further identified several brain regions with atypical function and anomalous structure in dyslexia, including left temporoparietal areas, which are thought to be involved in letter-to-sound conversions in reading (1-8, 13-18), the left middle-superior temporal cortex, which is thought to be involved in speech sound analysis (17)(18)(19)(20)(21)(22), and the left inferior temporo-occipital gyrus, which may function as a quick word form recognition system (18,20,(22)(23)(24)(25)(26)(27). Together, these findings support a prominent neurophysiological model of reading skill acquisition and its disorders according to which dyslexia is associated with atypical structural and functional development of posterior brain systems (1-10).The neural circuits involved in reading and reading disorders may vary across languages, because of differences in how a writing system links print to spoken language (4-7, 28-30). For example, in logographic Chinese, graphic forms (characters) are mapped to syllables, which differs markedly fr...

Writing quality predicts Chinese learning

“…Writing-reading connections were demonstrated in correlational studies with normal and dyslexic (Chan et al, 2006) Chinese children, and functional brain-imaging has shown that judging visual words involves brain areas possibly associated with writing (Siok, Niu, Jin, Perfetti, & Tan, 2008). Taken together, accumulating behavioral and neuroimaging research supports the hypothesis that writing experience contributes to reading skill in Chinese L1 literacy Siok et al, 2008). Henceforth, several recent empirical studies have extended these writing-on-reading effects to Chinese written language in an adult second languagelearning context.…”

“…Once the motor memory has been learned and stabilized, it can last for long periods, and behavioral studies indicate that sensorymotor memory traces, inferable from stroke sequences in partial character primes, facilitate character recognition (Flores d'Arcais, 1994). Writing-reading connections were demonstrated in correlational studies with normal and dyslexic (Chan et al, 2006) Chinese children, and functional brain-imaging has shown that judging visual words involves brain areas possibly associated with writing (Siok, Niu, Jin, Perfetti, & Tan, 2008). Taken together, accumulating behavioral and neuroimaging research supports the hypothesis that writing experience contributes to reading skill in Chinese L1 literacy Siok et al, 2008).…”

Graphical Modification of Text. An Approach To Dyslexic Users.

“…("fish", visually). The finding, reported in Proceedings of the National Academy of Sciences (Siok et al, 2008) surprisingly shows that there is significant difference in ability to decode words in different languages.…”

Cross-Cultural/Linguistic Differences in the Prevalence of Developmental Dyslexia and the Hypothesis of Granularity and Transparency

“…Other brain imaging studies using fMRI (functional Magnetic Resonance Imaging) in Chinese such as Siok, Niu, Jin, Perfetti, and Tan (2008) or Siok, Perfetti, Jin, & Tan (2004) revealed functional and structural abnormalities in the left middle frontal gyrus of Chinese dyslexic children, but not in the left temporoparietal and occipitotemporal regions that are important for reading in alphabetic languages (e.g., Paulesu, McCrory, et al, 2000;Wydell, Vuorinen, Helenius & Salmelin, 2003), and are typically compromised in dyslexic children in alphabetic languages (e.g., Horwitz, Rumsey, & Donohue, 1998;Temple, Poldrack, Salidis, Deutsch, Tallall, Merzenich, & Gabriel, 2001). These researchers therefore argued that reading Chinese characters might require firstly greater cognitive demand for visual processing than reading in alphabetic languages such as English, and secondly a greater inter-activity between orthography and phonology.…”