Abstract
Many alphabetic studies have evidenced that individuals with developmental dyslexia (DD) have deficits in visual magnocellular (M) pathway. However, there are few studies to investigate the M function of Chinese DD. Chinese is a logographic language, and Chinese characters are complicated in structure. Visual skills and orthographic processing abilities are particularly important for efficient reading in Chinese as compared to alphabetic languages. Therefore, it is necessary to investigate the visual M function of Chinese DD and whether the M function was associated with orthographic skills. In the present study, 26 dyslexic children (mean age: 10.03 years) and 27 age-matched normal children (mean age: 10.37 years) took part in a coherent motion (CM) detection task and an orthographic awareness test. The results showed that dyslexic children had a significantly higher threshold than age-matched children in CM detection task. Meanwhile, children with DD responded more slowly in orthographic awareness test, although the group difference was marginally significant. The results suggested that Chinese dyslexics had deficits both in visual M pathway processing and orthographic processing. In order to investigate the relationship between M function and orthographic skills, we made a correlation analysis between CM threshold and orthographic awareness by merging performance of dyslexic children and age-matched children. The results revealed that CM thresholds were positively correlated with reaction times in orthographic awareness test, suggesting that better M function was related to better orthographic processing skills.
Highlights
Developmental dyslexia (DD) is a neurobiological reading disorder
The performance in orthographic awareness test and coherent motion (CM) detection task of DD group and age-matched control (CA) group was shown in Table 2 and Figure 1. t-test revealed that the CM threshold of DDs was significantly higher than that of CA [t(51) = 2.76, p < 0.01, d = 0.77]
In order to explore the relationship between orthographic processing skills and the performance in CM detection, we made a correlation analysis between average reaction time (RT) to pseudo-characters and non-characters and CM threshold by merging the data of two groups
Summary
Developmental dyslexia (DD) is a neurobiological reading disorder. Individuals with DD have difficulties in accurate or fluent word recognition, spelling, and word decoding despite adequate instruction and intelligence (Lyon et al, 2003). The deficits in temporal auditory processing were confirmed in event-related potential (ERP) and functional magnetic resonance imaging (fMRI) studies (e.g., McAnally and Stein, 1997; Kujala et al, 2000, 2003; Temple et al, 2000; Paul et al, 2006; Stoodley et al, 2006; Gaab et al, 2007; Khan et al, 2011). These results consistently revealed that dyslexics have deficits in temporal auditory processing in alphabetic languages
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