A topographic event-related potential follow-up study on 'prepulse inhibition' in first and second episode patients with schizophrenia

Dopamine agonists impair and antagonists normalize prepulse inhibition (PPI ) of startle and gating of the P50 event-related potential (ERP), but the w ithin-subject effect of treatment on impaired gating in schizophrenia has n ot been studied. We report the first results of a longitudinal study using PPI of ERPs as a measure of sensory gating in an auditory Go/NoGo discrimin ation. After admission and approximately 3 months later, at discharge, 15 p atients with schitophrenia performed a discrimination between a 1.4 kHz tar get tone and an 0.8 kHz non-target tone with no prepulse, or with a prepuls e at 100 ms or 500 ms before either tone. ERPs were recorded from 19 sites. Healthy subjects were studied twice, with 3 months between sessions. PPI o f the P50 peak in the 100-ms condition was reduced in patients on admission . At discharge, decreased negative symptoms correlated with enhanced PS0-PP I at frontocentral sites. After treatment increased N100-PPI at centrotempo ral sites correlated with fewer positive symptoms. At frontal sites in the 100-ms condition, the initially small difference of non-target minus target P300 amplitudes increased as negative symptoms decreased. It is concluded that weak auditory prepulses interfere with early auditory stimulus process ing (P50), channel selection (N100) and selective attention (P300). Gating of these stages of processing is impaired in psychotic patients and treatme nt tends to normalize gating in tandem with improvements of different types of symptoms. (C) 1999 Elsevier Science Ireland Ltd. All rights reserved.