Functional MRI results guided ROI selection & probability map making on DTI study: the white matter route for orthography-to-phonology transformation in Chinese

Introduction Reading involves complex information processes, and most of all it needs expertise in transforming the visual word form into auditory representation, namely orthography-to-phonology transformation (OPT). There are two theories debating about the information processes in OPT. Dural-route theory [1] asserts two independent routes responsible for processing highly used or irregular words as well as words of pronunciation highly accordant to the spelling-to-sound rules, respectively. However, the connectionist view in OPT supports words of different kinds are processed in the same circuitry. The differences in using frequency and spelling regularity come from the processing depth and the level of neuronal activation in stead [2]. The writing system in Chinese is quite different from the alphabetic ones, because the former needs deeper orthography processing. The neural substrates for OPT of Chinese characters were revealed in the fMRI research study of Lee et al., [3], and result showed the brain activation patterns were similar across different depth of OPT processing. In the present study, the first goal was to use diffusion tensor imaging (DTI) to delineate possible connection between the main activated foci for OPT in Chinese. The superior longitudinal fasciculus (SLF) in the left brain was the main concern for analysis, for the reason that it is believed to involve in the language process. Finding the correlation between the white matter indices and the reaction time of word naming was the second goal to investigate whether the tracts play important roles in the processing of OPT.