Objective: We investigated the nature of the memory impairment in schizophr
enia 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. P
articipants responded to occasional target words. Half of the non-target wo
rds 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 tho
se to non-repeated words, though this positive-going effect was attenuated
in the schizophrenics, especially around 400-500 ms. The effect at lag 5 wa
s 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 cont
rols but not in schizophrenics, whereas a peak increment in the late positi
ve component induced by word repetition at both lags was observed in both g
Conclusions: Findings indicate that patients with schizophrenia have a defi
cit in a brain process modulating ERP correlates of memory, when words are
repeated immediately. This deficit might be related to an abnormal N400 pri
ming effect in schizophrenia. (C) 2001 Elsevier Science Ireland Ltd. All ri