Magnetic brain activity elicited by visually presented symbols and Japanese characters

A standard model of word reading postulates that the posterior inferior temporal cortex is involved in the processing of written words. This processing probably occurs within 200 ms after stimulus presentation. In order to characterize this process more precisely, we conducted a MEG study during a reading task in nine right-handed normal Japanese subjects. The subjects were required to respond to a word pertaining to the human body so that all stimuli would be subject to the same semantic processing. The trials for non-target conditions, such as kanji words, meaningful kana words, kana pseudowords and symbols were analysed to avoid possible P300 effect. The magnetic response peak of around 200 ms for symbols was smaller than any of the other three letter conditions. This result may suggest that M200 reflects the word-specific process such as visual word form recognition.