Scrambling effects on the processing of Japanese sentences: An fMRI study

The present study aims to confirm the cortical correlates of scrambling effects, a free word order phenomenon that has been observed in a variety of cross-linguistic investigations but whose mechanism still remains unclarified. Many syntax-oriented hypotheses on scrambling have been provided to develop the structural basis of the free word order permutation in Japanese, leading to the most recent phrasal architecture, in which the object noun phrase of a transitive sentence “moves” to a higher position than the subject to form an asymmetric structure including antecedent–gap relationships. Such a configurational structure formed by scrambling operation predicts that the scrambled sentences have a more complex structure than canonical sentences, and that the former requires a greater burden on cognitive processes in related areas within the brain. Based on this general assumption, we employed an experimental method of whole-sentence presentation of Japanese transitive sentences, for both canonical transitive sentences (Subject–Object–Verb) and their scrambled counterparts (Object–Subject–Verb). The result showed more activation at the left inferior frontal gyrus (IFG) and the left dorsal prefrontal cortex (DPFC) during the comprehension of scrambled sentences than that of canonical sentences. This indicates, in accordance with previous findings on scrambling from neurolinguistic perspectives, that the scrambling in Japanese is indeed one of the grammatical operations and that the parsing strategy for the asymmetric antecedent–gap relationship demands an additional cognitive activation in the brain.