Developmental differences of neuro-cognitive networks for orthographic and phonological processing in Chinese words

This dissertation investigated developmental differences in brain activation during orthographic and phonological processing of Chinese words using functional magnetic resonance imaging (fMRI). We employed rhyming and spelling tasks in the visual and auditory modalities in third-graders, fifth-graders and adults. Consistent with many previous developmental neuroimaging studies, we found developmental increases in left dorsal inferior frontal gyrus for all tasks, suggesting greater lexical control over age. Behavioral studies in Chinese reading suggest that there is a developmental increase in reliance on visuo-orthographic processes and a decrease in reliance on phonology. Consistent with this, in both visual tasks, we showed developmental increases in bilateral occipito-parietal regions, whereas there were developmental decreases in left superior temporal gyrus. Although there were decreases in left superior temporal gyrus in the visual tasks, there were developmental increases in left superior temporal gyrus in both auditory tasks, suggesting more elaborated phonological input representations. The left superior temporal gyrus in the auditory tasks was early maturing compared to frontal regions that showed prolonged changes after 11 years old. The auditory tasks also showed task specific activation of regions involved in visuo-orthographic processing. In the rhyming task, there were developmental decreases in left fusiform gyrus, suggesting less automatic activation orthographic representations during spoken word processing. However, when the task required access of spellings, there were developmental increases in left inferior temporal gyrus suggesting greater engagement of orthographic processes. The current study shows that the structure of the Chinese language influences the development of the lexical processing network in the brain.