The relationship between language processing of Kanji and Kana and ERP in aphasia

Background. It has been suggested that the N400 component of event-related potentials (ERP) reflects language processing. Methods. We investigated this potential of aphasic patients with some impairment in language processing. Japanese Kanji and Kana words were used as stimuli under the two oddball paradigms tone consisted of Kanji words, the other consisted of Kana words). Generally, in language processing, Kana words are always processed and comprehended in terms of their phonology. On the other hand, Kanji words are dominated by direct transcoding to meaning. Results. There was no clear ERP difference between Kanji and Kana. However, after the vicinity of 400 ms, aphasia had a smaller potential in the Kanji and Kana tasks than the control. Meanwhile, in the section from about 400 ms to about 800 ms, the control had a larger negative potential which was different in the two tasks about strength and process of potential. Conclusions. The reduced potential in aphasia is thought to be related to inactive semantic memory search. Also the potential difference between the Kanji and Kana tasks in the control is thought to depend on the difference in semantic memory search that is based on stimulus contents.