Examining Cortical Activation for the Primacy of Syntactic over Semantic Processing in Japanese Process: A Study Using Near-Infrared Spectroscopy

In the present study, we examined the primacy of syntactic over semantic processing in the Japanese language, in which grammatical morphology is as prominent as in most of Indo-European languages, but it also possesses symbolic language, similar to Chinese. Three kinds of collocation were created as stimuli: congruous collocations, collocations with semantic violation, and collocations with syntactic violation. Participants were asked to read the stimuli silently and then they judged whether they had seen them or not. Near-infrared spectroscopy was used to measure the regional changes in hemoglobin concentration in the brain of the participants. After analyzing the interplay of cortical activation between syntactic and semantic processing, we found that, during the reading task, when congruous stimuli were presented, activation was observed around the inferior frontal gyms and the middle temporal gyms, while when semantically violated stimuli were presented, activation was observed around the inferior frontal gyms. However, no brain area activation was observed for a syntactic violation condition. These activation patterns suggest that in Japanese, semantic processing is also dependent on the intactness of syntactic information, just as in Indo-European languages. The present study indicates that languages with prominent grammatical morphology exhibit primacy of syntax over semantics, and that near-infrared spectroscopy provides an efficient method of evaluating the primacy of syntactic and semantic processes.