A meta-analysis of functional neuroimaging studies of dyslexia in alphabetic words and chinese characters.
Kwok, Fu Yu.
Date of Issue2013
School of Humanities and Social Sciences
Dyslexia is a learning disability that impairs one’s fluency in reading. It is estimated that about 5-17% of the population has dyslexia (Shaywitz & Shaywitz, 2001). Majority of the past studies on dyslexia were based on the English language. Nevertheless, in the past few years, studies of dyslexia in other languages such as Chinese language are slowly increasing. With the recent development of neuroimaging techniques such as fMRI, research trend has also shifted from examining the effect of dyslexia at the behavioral level to the brain level, which aids in the understanding of the neural basis of dyslexia. Thus far, three meta-analyses have been published on dyslexia in the alphabetical languages (Maisog, Einbinder, Flowers, Turkeltaub, & Eden, 2008; Richlan, Kronbichler, & Wimmer, 2009, 2011). However, no meta-analytic study has been conducted for non-alphabetical languages such as the Chinese language. Hence, this study is the first meta-analysis examining the effect of dyslexia in the Chinese language. Results from the Chinese language meta-analysis study replicates the results from previous empirical studies showing low activation primarily in areas such as the left middle frontal gyrus and the right middle occipital gyrus (Liu et al., 2012; Siok, Niu, Jin, Perfetti, & Tan, 2008; Siok, Perfetti, Jin, & Tan, 2004; Siok, Spink, Jin & Tan, 2009; Yang, 2005). In addition, functional neuroimaging single studies examining the effect of dyslexia in both alphabetical languages and Chinese language have shown that there are differences in the brain activations between these languages (Paulesu et al., 2001; Richlan et al., 2010; Siok et al., 2004). Using the meta- analysis technique, this study provides the first analysis comparing the effect of dyslexia between the alphabetical languages and the Chinese language. Lastly, the cross language generalizability of the two main theories of dyslexia (i.e. the phonological theory and the cerebellar theory) are also examined using functional neuroimaging data.