Modulation of language processing in schizophrenia: Effects of context andhaloperidol on the event-related potential

Background: Disturbances in language associations were among the first clin ical symptoms reported for individuals described as schizophrenic (Bleuler 1911/ 1950), Currently, associative language disturbance is a diagnostic fe ature of schizophrenia (American psychiatric Association 1994); however, th e mechanisms that produce this symptom remain unknown. In the present study two candidate psychological functions were examined: sensitivity to semant ic context and expectancy (attention). Methods: Visual event-related potentials were recorded during a lexical dec ision task in which semantic relationship and expectancy (relatedness propo rtions) were varied Semantic priming processes were compared between 34 mal e normal control subjects tested once and 37 male schizophrenic inpatients evaluated during their participation iii a double-blind haloperidol mainten ance therapy and placebo replacement protocol. Results: Schizophrenic patients failed to discriminate between associated a nd unassociated words, as measured by the amplitude of the N400 component ( i.e., absence of the N400 priming effect); however, the overall mean amplit ude of N400 did nor differ between patients and control subjects. In additi on, patients and control subjects did not differ significantly in the ampli tude of N400 elicited to associated words or to unassociated words. Finally , the effect of expectancy-based processing oil the magnitude of the N400 p riming effect did nor differ between patients and control subjects. Conclusions: On the basis of these findings, a tentative hypothesis is sugg ested that schizophrenic patients are characterized by a pattern of indiscr iminate or random spread of activation in their semantic network during the processing of single-word semantic contexts. Biol Psychiatry 1999;45:1336- 1355 (C) 1999 Society of Biological Psychiatry.