Kitade, Shuko Department of Physiology, The University of Tokushima School of Medicine|Department of Speech Therapy, Kagawa Rehabilitation Center
Enai, Toshihiro Department of Education for Handicapped, School of Education, The University of Kagawa
Sei, Hiroyoshi Department of Physiology, The University of Tokushima School of Medicine Tokushima University Educator and Researcher Directory KAKEN Search Researchers
Morita, Yusuke Department of Physiology, The University of Tokushima School of Medicine Tokushima University Educator and Researcher Directory
Although the N400 component of event-related potentials (ERPs) is suggested to reflect language processing, exactly which language processing functions N400 is sensitive to is not clear. We investigated this component in aphasic patients with some impairments of language processing. Meaningful and meaningless words in Kana (Japanese characters) were used as stimuli under a visual oddball paradigm. Increases in N400 latency and amplitude in the aphasic group were significant in comparison with the control group. In the aphasic group, N400 latency correlated significantly with the performance intelligence quotient employed besides language quotients. Moreover, the N400effects were seen more clearly in the left hemisphere than in the right hemisphere for both groups.
We propose that the abnormal variations in amplitude or latency of N400 in the aphasic group reflect language processing functions (controlled processing and automatic processing) that are different between slight and severe cases of aphasia. Moreover, N400 effects are sensitive to intellectual abilities besides language ability. We also suggest that N400 effects in the left hemisphere for the aphasic group are a reflection of active language processing as the substitution function.
The journal of medical investigation : JMI
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