Similar alterations in brain function for phonological and semantic processing to visual characters in Chinese dyslexia

Abstract

Dyslexia in alphabetic languages has been extensively investigated and suggests a central deficit in orthography to phonology mapping in the left hemisphere. Compared to dyslexia in alphabetic languages, the central deficit for Chinese dyslexia is still unclear. Because of the logographic nature of Chinese characters, some have suggested that Chinese dyslexia should have larger deficits in the semantic system. To investigate this, Chinese children with reading disability (RD) were compared to typically developing (TD) children using functional magnetic resonance imaging (fMRI) on a rhyming judgment task and on a semantic association judgment task. RD children showed less activation for both tasks in right visual (BA18, 19) and left occipito-temporal cortex (BA 37), suggesting a deficit in visuo-orthographic processing. RD children also showed less activation for both tasks in left inferior frontal gyrus (BA44), which additionally showed significant correlations with activation of bilateral visuo-orthographic regions in the RD group, suggesting that the abnormalities in frontal cortex and in posterior visuo-orthographic regions may reflect a deficit in the connection between brain regions. Analyses failed to reveal larger differences between groups for the semantic compared to the rhyming task, suggesting that Chinese dyslexia is similarly impaired in the access to phonology and to semantics from the visual orthography.

Neural specialization of phonological and semantic processing in young children

“…Alternatively, the lack of specialization in the left IFG in the current study might be due to a low sensitivity of the specific task or analyses used in this study. It could be that a more demanding task or a different analysis approach, such as a multi-variate parametric analysis (MVPA), could reveal a double-dissociation between phonological- and semantic-related activation within the left IFG in preschool children, as demonstrated in school-age children (Bach et al, 2010; Cao et al, 2009; Liu et al, 2012). …”

“…Only a few studies have examined the double-dissociation between phonological-related (rhyming judgment) and semantic-related (meaning judgment) tasks in school-age children using visual stimuli (Bach et al, 2010; Cao et al, 2009; Landi et al, 2010; Liu et al, 2012). The study in English (Landi et al, 2010) used a mixed stimuli presentation (orthographic and pictorial) and found greater semantic-related activation in the left STG and AG, as compared to phonological-related activation.…”

Holistic neural coding of Chinese character forms in bilateral ventral visual system

“…The holistic encoding hypothesis proposes that Chinese characters, despite their diverse stroke patterns, are holistically encoded as a whole perceptual unit involving no independent, intermediate representations of sub-character components (Dehaene et al, 2005;Liu & Perfetti, 2003;Tan et al, 2000;Wong et al, 2012). In support of this idea, previous studies have revealed Chinese-specific engagement of the right visual cortex in addition to its left hemisphere counterpart (Cao et al, 2009;Liu et al, 2012;Tan et al, 2000), which has been shown essential for holistic processing (Kosslyn et al, 1993;Smith et al, 1995). However, the exact functional role of right visual cortex in character recognition remains unclear because this brain system might also be involved in coordination and integration of multiple visual objects given its essential contribution to visuospatial processing (Clements et al, 2006;Corballis, 2003;Ng et al, 2000).…”

“…Regional BOLD signal change relative to fixation baseline was calculated for each primary condition. Given its essential involvement in Chinese character recognition reported in previous studies, we placed our primary interest in the bilateral visual cortex (Cao et al, 2010;Liu et al, 2012;Siok, Perfetti, Jin, & Tan, 2004;Siok, Spinks, Jin, & Tan, 2009;Tan et al, 2000). However, we did not specifically focus on any specific regions within the visual system, e.g.…”

Translating Scientific Progress in Dyslexia into Twenty-first Century Diagnosis and Interventions

“…Other studies of Chinese dyslexia have reported reduced activation in bilateral occipito-temporal regions and left middle frontal gyrus (Siok et al, 2004;Siok et al, 2008;Siok et al, 2009), regions not generally found in fMRI studies of dyslexia in alphabetic orthographies. A more recent study demonstrated reduced activation for Chinese dyslexics in right occipital cortex, consonant with a language-specific role of right visual cortex in Chinese reading and suggesting a deficit in holistic visuo-orthographic analysis in Chinese dyslexia (Liu et al, 2012).…”