Neurofunctional basis underlying audiovisual integration of print and speech sound in Chinese children

Effortless print-sound integration is essential to reading development, and the superior temporal cortex (STC) is the most critical brain region. However, to date, the conclusion is almost restricted to alphabetic orthographies. To examine the neural basis in non-alphabetic languages and its relationship with reading abilities, we conducted a functional magnetic resonance imaging study in typically developing Chinese children. Two neuroimaging-based indicators of audiovisual processing—additive enhancement (higher activation in the congruent than the average activation of unimodal conditions) and neural integration (different activations between the congruent versus incongruent conditions)—were used to investigate character-sounds (opaque) and pinyin-sounds (transparent) processing. We found additive enhancement in bilateral STCs processing both character and pinyin stimulations. Moreover, the neural integrations in the left STC for the two scripts were strongly correlated. In terms of differentiation, first, areas beyond the STCs showed additive enhancement in processing pinyin-sounds. Second, while the bilateral STCs, left inferior/middle frontal and parietal regions manifested a striking neural integration (incongruent > congruent) for character-sounds, no significant clusters were revealed for pinyin-sounds. Finally, the neural integration in the left middle frontal gyrus for characters was specifically associated with silent reading comprehension proficiency, indicating automatic semantic processing during implicit character-sound integration. In contrast, the neural integration in the left STC for pinyin was specifically associated with oral reading fluency that relies on grapho-phonological mapping. To summarize, this study revealed both script-universal and script-specific neurofunctional substrates of print-sound integration as well as their processing- and region-dependent associations with reading abilities in typical Chinese children. Highlights The bilateral superior temporal cortices display additive enhancement in processing print-sound information regardless of orthographies. The location, direction, and strength of the neural audiovisual integration are modulated by orthographic transparency. The neural integration in the left middle frontal gyrus in processing character-sounds is correlated to reading comprehension. The neural integration in the left superior temporal gyrus for pinyin is correlated with oral reading fluency. The neural integrations of character-sounds and pinyin-sounds show spatial overlap and inter-subject correlation in the left superior temporal cortex.