Fig. 1: Experimental paradigm, sEEG recordings, and hypothesis regarding the processing dynamics of speech production.

A Schematic diagram of the experimental paradigm. Following a fixation, a visual single-character Chinese word was presented. Participants were asked to speak out the word as quickly and accurately as possible when the word was displayed on the screen. (Please refer to the Methods for detailed parameters.) B The coverage of electrode contacts in all participants. C Regions of interest (ROIs) according to the hypothesis about the processing dynamics of speech production. On the left, 5 anatomically defined ROIs are depicted. These ROIs are the areas that mediate three major processes during the read-aloud task, including visual word code (vpIOG & pFG), auditory phonological code (HG & pSTG), and motor-related phonological & phonetic encoding (IFG). On the right, individual contacts are superimposed on the contour of each ROI, demonstrating the distribution of coverage. Smaller dots represent task-related contacts, while larger dots denote the onset-activated contacts. The pie chart summarizes the number of contacts in each ROI that were used in the analyses. The crucial investigation is to assess the temporal order of activation among the ROIs in the auditory and motor systems that mediate the three key processes, as indicated by the arrows.