Processing Asymmetry in Object-modifying Relative Clauses: Evidence from Functional Connectivity

Relative clauses (RCs) can be used to recursively embed structures in sentences. Subject-modifying (SM) RCs have been widely used to examine whether there is asymmetry in the ease of processing subject-extracted RCs (SRCs) and object-extracted RCs (ORCs) in Chinese. However, the difference in the beginning sequence of SM-SRCs (verb-noun) and SM-ORCs (noun-verb) may have been a confound in these tests. Unlike SM-RCs, Chinese object-modifying (OM)-RCs are initiated by the same noun-verb sequence. In the current study, participants were asked to read OM clauses (OM-SRCs and OM-ORCs) in Chinese sentences while undergoing fMRI scanning. Activation and Granger causality analyses were both conducted. There were no significant differences in activation elicited by OM-SRCs and OM-ORCs. In contrast, the results of Granger causality analyses showed more ORC-specific connectivity than SRC-specific connectivity, especially from left inferior frontal gyrus to superior temporal gyrus regions, which suggests that ORC processing required more interregional interaction in the brain compared with SRC processing. Taken together, these findings indicate an SRC advantage in processing Chinese OM-RC sentences and that the advantage is more involved in functional connectivity rather than activation. The results support the structural distance hypothesis about RC processing.