Neuroanatomical representation of language in English- Chinese bilingual biscriptals: An FMRI study

Abstract

To date, neuroimaging experiments involving English-Chinese bilinguals suggest that common brain areas subserve the two languages. Given that the oral and written forms of English and Mandarin differ so markedly, and differences have been reported for bi-alphabetic readers, the null findings for English-Chinese bilinguals warrant a systematic investigation. In this thesis, the language representation of skilled English-Chinese bilingual biscriptals was investigated at the orthographic, phonological and semantic levels at both the cognitive and neuroanatomical levels, using equivalent behavioural (N = 28) and fMRI (n = 6) experiments. The three experimental tasks (lexical decision, homophone matching and synonym judgement) employed in this study were developed from a cognitive model of skilled reading with the additional assumption of modularity in language processing. The behavioural data (reaction times and error rates) were used to gauge task demands across the two languages, and the neuroanatomical correlates for English and Mandarin were compared. The pattern of activations observed for the English-Chinese bilingual biscriptals showed strong consistencies with past neuroimaging studies that investigated the neural correlates of language processing in English and Mandarin unilinguals, although the bilinguals showed less left lateralization. More importantly, and contrary to previous fMRI studies, a number of different brain regions were activated for English and Mandarin at the level of orthography, phonology and semantics. The neuroanatomical representation of English-Chinese bilingual biscriptal reading and its theoretical implications are discussed in detail.