Seiki Ayano

An event-related fNIRS investigation of Japanese word order

Japanese is a free word-order language, and allows both subject–object–verb (SOV) and object–subject–verb (OSV) orders. Our previous study using near-infrared spectroscopy (NIRS) imaging revealed that OSV sentences induce more activation in the left frontal lobe than SOV sentences. The present study develops our previous experiment: (1) by adopting an event-related design, and (2) by using sentences involving the adverb naze ‘why’, which plays a prominent role in recent linguistic studies. The results of our new experiment indicated that the cerebral activation in OwhySV sentences was significantly larger than that in SwhyOV sentences, in the right anterior prefrontal region, which is consistent with the assumption that OwhySV order is derived from SwhyOV order. We speculate that the activation observed in the anterior prefrontal cortex during the processing of the sentences involving ‘why’ might be due to the processing of higher-order function in the cerebral cortex.

A functional near-infrared spectroscopy study on the basic word order in Japanese

To determine the basic word order in Japanese, oxyhemoglobin concentration changes in the frontal region of 32 healthy men were measured by near-infrared spectroscopy. Our experiment used four types of sentences: (i) subject-object-verb (SOV), (ii) object-subject-verb (OSV), (iii) subject-naze (why)-object-verb (SwhyOV), and (iv) naze (why)-subject-object-verb (whySOV). The results have shown that although oxyhemoglobin changes in the OSV sentences were significantly larger than those in the SOV sentences in the left frontal lobe, such effects were not observed between SwhyOV sentences and whySOV sentences. These results are consistent with the view that both SwhyOV and whySOV are the basic, which suggests that neurolinguistic evidence has the potential to provide an important basis for determining the basic word order in a free word-order language.

Cortical activation by syntactic violations in Japanese: an fNIRS study

To investigate the neural correlates of proficiency in second language, we analyzed T1-weighted 3-dimensional structural MRIs obtained from 27 healthy, dextral, native Japanese who had learnt English as a second language. The English Vocabulary Test (EVT) was employed as a representative measure of proficiency in English. The gray matter was segmented from each structural MRI, spatially normalized to fit into a standard gray-matter template, and smoothed with a 12-mm Gaussian kernel (SPM5). A voxel-based morphometry analysis incorporated EVT scores, age and sex. The EVT score was correlated with gray matter volumes in the bilateral inferior frontal gyri, bilateral caudate nuclei, right middle frontal gyrus, and left middle temporal gyrus (p < 0.001 uncorrected, voxel size >150). Structural changes in a set of cortical and subcortical regions might underlie proficiency in second language.