This present study identified an optimal model representing the relationship between orthography and phonology in Chinese handwritten production using dynamic causal modeling, and further explored how this model was modulated by word frequency and syllable frequency. Each model contained five volumes of interest in the left hemisphere (angular gyrus [AG], inferior frontal gyrus [IFG], middle frontal gyrus [MFG], superior frontal gyrus [SFG], and supramarginal gyrus [SMG]), with the IFG as the driven input area. Results showed the superiority of a model in which both the MFG and the AG connected with the IFG, supporting the orthography autonomy hypothesis. Word frequency modulated the AG → SFG connection (information flow from the orthographic lexicon to the orthographic buffer), and syllable frequency affected the IFG → MFG connection (information transmission from the semantic system to the phonological lexicon). This study thus provides new insights into the connectivity architecture of neural substrates involved in writing.

Writing is an important way to communicate in everyday life because it can convey information over time and space, but its neural substrates remain poorly known. Although the neural basis of written language production has been investigated in alphabetic scripts, it has rarely been examined in nonalphabetic languages such as Chinese. The present functional magnetic resonance imaging study explored the neural substrates of handwritten word production in Chinese and identified the brain regions sensitive to the psycholinguistic factors of word frequency and syllable frequency. To capture this, we contrasted neural activation in “writing” with “speaking plus drawing” and “watching plus drawing.” Word frequency (high, low) and syllable frequency (high, low) of the picture names were manipulated. Contrasts between the tasks showed that writing Chinese characters was mainly associated with brain activation in the left frontal and parietal cortex, whereas orthographic processing and the motor procedures necessary for handwritten production were also related to activation in the right frontal and parietal cortex as well as right putamen/thalamus. These results demonstrate that writing Chinese characters requires activation in bilateral cortical regions and the right putamen/thalamus. Our results also revealed no brain activation associated with the main effects of word frequency and syllable frequency as well as their interaction, which implies that word frequency and syllable frequency may not affect the writing of Chinese characters on a neural level.