Fusiform Gyrus Laterality in Writing Systems with Different Mapping Principles: An Artificial Orthography Training Study

Writing systems vary in many ways, making it difficult to account for cross-linguistic neural differences. For example, orthographic processing of Chinese characters activates the mid-fusiform gyri (mFG) bilaterally, whereas the processing of English words predominantly activates the left mFG. Because Chinese and English vary in visual processing (holistic vs. analytical) and linguistic mapping principle (morphosyllabic vs. alphabetic), either factor could account for mFG laterality differences. We used artificial orthographies representing English to investigate the effect of mapping principle on mFG lateralization. The fMRI data were compared for two groups that acquired foundational proficiency: one for an alphabetic and one for an alphasyllabic artificial orthography. Greater bilateral mFG activation was observed in the alphasyllabic versus alphabetic group. The degree of bilaterality correlated with reading fluency for the learned orthography in the alphasyllabic but not alphabetic group. The results suggest that writing systems with a syllable-based mapping principle recruit bilateral mFG to support orthographic processing. Implications for individuals with left mFG dysfunction will be discussed.