Effects of sentence context on lexical ambiguity resolution in patients with schizophrenia.

Previous research has suggested that a failure in processing contextual information may account for the heterogeneous clinical manifestations and cognitive impairments observed in schizophrenia. In the domain of language, context processing in schizophrenia has been investigated mostly with single-word semantic priming paradigms; however, natural language comprehension depends on more than semantic relations between words. The present study aimed to systematically assess sentence context effects in homonym meaning activation in patients with schizophrenia. Fourteen patients with schizophrenia and 14 normal controls matched to the patients on sex, age, education and parental education, were examined using a cross-modal priming paradigm. Primes were sentences biasing the first, second, or neither meaning of a sentence-final equibiased homonym; targets were related to either the first or the second meaning of the homonym and appeared after an interstimulus interval (ISI) of 0ms or 750ms. Patients with schizophrenia exhibited a trend towards facilitation of both target types following unbiased sentences at ISI=0ms, similar to controls. However, in contrast to the pattern of selective target facilitation exhibited by control subjects following first- or second meaning-biased sentences, no significant target facilitation was observed in patients in the same condition. At ISI=750ms, patients did no longer exhibit significant target facilitation in any sentence context condition. This pattern of results is compatible with the assumption of a combined impairment in lexical (automatic spreading of activation within the semantic network) and extralexical (working memory) processes in patients with schizophrenia.