Impairment of an event-related potential correlate of memory in schizophrenia: effects of immediate and delayed word repetition.
OBJECTIVE
We investigated the nature of the memory impairment in schizophrenia using an event-related potential (ERP).


METHODS
Visual ERPs were recorded while 20 schizophrenics and 20 controls performed semantic categorization tasks with incidental word repetitions. Participants responded to occasional target words. Half of the non-target words were repeated immediately after initial presentation (lag 0) or after 5 intervening words (lag 5).


RESULTS
In both groups, ERPs to words at lag 0 were more positive than those to non-repeated words, though this positive-going effect was attenuated in the schizophrenics, especially around 400-500 ms. The effect at lag 5 was smaller and shorter than that at lag 0 but was comparable between groups. Attenuation of the N400 peak occurred for word repetition at lag 0 in controls but not in schizophrenics, whereas a peak increment in the late positive component induced by word repetition at both lags was observed in both groups.


CONCLUSIONS
Findings indicate that patients with schizophrenia have a deficit in a brain process modulating ERP correlates of memory, when words are repeated immediately. This deficit might be related to an abnormal N400 priming effect in schizophrenia.
Department of Psychiatry, Tohoku University School of Medicine, Sendai 980-8574, Japan. matsumo@psy.med.tohoku.ac.jp
K
K
Matsumoto
H
H
Matsuoka
H
H
Yamazaki
H
H
Sakai
T
T
Kato
N
N
Miura
M
M
Nakamura
K
K
Osakabe
H
H
Saito
T
T
Ueno
M
M
Sato
D000328:Adult; D000704:Analysis of Variance; D004569:Electroencephalography; D005074:Evoked Potentials, Visual / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D008569:Memory Disorders / Q000503:physiopathology*; D011932:Reading; D012559:Schizophrenia / Q000503:physiopathology*; D013997:Time Factors