Better early than late for a filler: An fMRI study on the filler-gap order in language

The neural substrates of syntactic movements have been heavily investigated; however, little attention was paid to the fact that there was a cross-linguistic preference for filler-before-gap (filler-first) to gap-before-filler (gap-first) structures in subject-verb-object (SVO) languages. This fMRI study aimed to explore whether there was a cognitive basis for such a preference. Different filler-gap orders resulting from various syntactic movements were tested in Chinese: topicalization (filler-first) and relativization (gap-first, including subject and object relative clauses). The data showed that gap-first vs. filler-first contrasts activated the left anterior temporal gyrus (L-ATL) and sometimes the left thalamus. We argued that the L-ATL (and the left thalamus) was recruited because deeper semantic retrieval was performed on the verb to facilitate its merge with the gap for thematic role assignment. Our results provided a possible cognitive explanation for the preference for filler-first to gap-first structures in SVO languages.