The nature of syntactic working memory during relative clause processing: fMRI evidence from multiple anatomic ROIs

Relative clauses (RC) are a common embedded structure in natural language. They can be classified as Subject-extracted RC (SRC) and object-extracted RC (ORC). Previous studies have suggested an ORC advantage in Chinese. This is consistent with the memory-based theories, which propose that more syntactic working memory (SWM) is needed during the Chinese SRC processing than the ORC processing. However, it is still unclear about the nature of the SWM (language-specific vs. domain-general). In the current study, participants were asked to read Chinese SRC and ORC sentences while undergoing functional magnetic resonance imaging (fMRI) scanning. Because of the important role of the inferior frontal gyrus (IFG) and superior temporal gyrus (STG) in SWM, these two brain regions were divided into sub-regions. Critically, LIFG_orbital is more related to language-specific processing whereas LIFG_opercular is more related to domain-general processing. Activation analyses and Granger causality (GC) analyses were both conducted. The results first provided more neurophysiological evidence of the ORC advantage in Chinese. More importantly, the results of activation analyses showed that LIFG_oper was more activated in the contrast of SRC > ORC. In contrast, the results of GC analyses showed that LIFG_orb was more involved in the SRC-specific connectivity. Altogether, these results suggest that the SWM induced by the contrast of SRC > ORC was related to both the language-specific and domain-general processing.