Difference of semantic processing and character types in silent reading of words—a study using MEG

Abstract

To investigate the brain activity during the semantic processing of words within the context, magnetoencephalograph (MEG) was measured while subjects read the words silently. Four sets of Japanese passages were presented one word at a time consecutively. By using 148-channel whole head systems, the magnetic responses were compared among nouns written in kanji characters, nouns written in hiragana characters, and particles. There was an obvious magnetic response for all stimulus types around 200 ms. The nouns written in kanji showed the greatest response followed by the nouns written in hiragana and the particles, respectively. Using 38 channels of the occipital, temporal, and parietal areas of each of the hemispheres, equivalent current dipoles (ECDs) for the range of 150–250 ms were estimated to determine the locations of the brain activities. The ECDs for the nouns tended to be located in the posterior–inferior–temporal areas and for the particles, they were mainly located in the supramarginal and angular gyri.