| Research Abstract |
To obtain a more detailed description of the brain activity abnormalities that accompany linguistic processing in schizophrenia, we recorded magnetic responses using the BTi whole head system (148 channels) while health volunteer and schizophrenic subjects silently read Japanese sentences or word lists. Based on the across-subject root mean square (RMS) functions, a sequence of 2 components could be identified. The first component for the range of 100-250 msec (M200), equivalent current dipolar (ECD) sources of which were found in the fusiform gyrus bilaterally, were greater for nouns than for the particles and greater for kanji than hiragana. These results suggest that the M200 component may be related to word recognition. In addition, RMS for symbols was smaller than for words (kanji and hiragana), suggesting that at least a part of M200 might be involved in phonological processing. The second component for the 300-500 msec, peaking around 400 msec (M400), revealed a larger RMS for semantically incongruent words to the preceding context and unexpected words compared to semantically congruent words. For the former two conditions, ECD generators of the N400m were estimated in the vicinity of the supra and middle temporal gyrus in both hemispheres. No reliable between-condition difference of source localization of N400m was obtained. M400 was reduced in the schizophrenic patients, suggesting that the use of context may be poor in schizophrenia. However, ECD sources of M400 for the incongruent and unexpected words did not differ between the two groups. This result is consistent with the previous notion that the structure of language in schizophrenia is intact.
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