Probing into the underlying neural basis of reading in Chinese

Abstract

Burgeoning research has been done on reading and developmental dyslexia in different writing systems over the past decades. The prevailing view of reading research is that the left middle frontal gyrus (LMFG) is more strongly activated in reading logographic Chinese than in reading alphabetic scripts such as English. This region seems to also serve as a useful marker of Chinese dyslexia for it exhibits both functional and structural aberrations of the dyslexic brain (Siok et al., 2008). Although different groups of researchers have corroborated the association between the LMFG activation and Chinese reading across multifarious experimental task paradigms, the contributing factors of this region to reading performance in Chinese is still ill-defined. Behavioral studies do not appear to be capable of providing an adequate answer to this question either. Various processing skills –ranging from phonological, visual, orthographic, morphological, radical, rapid naming to handwriting –have all shown to reflect connections with reading in Chinese. Without a clear understanding of the exact core nature and the underlying neural basis of Chinese reading, it renders difficulties in providing early identification for potentially impaired readers and effective reading strategies for beginning readers and dyslexic individuals.

The present study, therefore, sought to annotate the determining functions of the LMFG in Chinese reading. Past research has characterized working memory as one of the pivotal functions of the LMFG, and speculated that reading might rely on this cognitive skill (Siok et al., 2004, 2008). Four distinct fMRI tasks, all consisting of the working memory component but varying in their respective processing skills, were reported. Task 1 and 2 focused on executive functioning skills; Task 3 and 4 emphasized visual-orthography and phonology respectively. 19normal-reading university students in the Mainland China participated in this neuroimaging study. All four tasks triggered the activity in the LMFG at BA 9, but significant correlations between brain activity of this region and Chinese reading performance were not obtained for all cases, except for contrasts of task conditions where in working memory involving executive control and phonological processes was being measured. It is comprehensible why they are critical to one’s Chinese reading ability when the linguistic features of Chinese are taken into consideration. Chinese character processing is likely to necessitate higher-level executive control on top of simple storage since it demands simultaneous coordination of multiple components –phonology, visual-orthography and semantics. The relationship between working memory with executive control and reading performance was further substantiated by the follow-up behavioral study on Grade 4 children.

The current findings have presented a clear line of evidence regarding the underlying factors in Chinese reading and underscored the role of working memory. This prominently contributes to future work on reading development and dyslexia.