Heterogeneity in cognitive functioning of schizophrenic patients evaluated by a lexical decision task

Background. The disorganization pattern in schizophrenia, which involves formal thought disorders, is thought to be correlated with a deficit in integrative processes of contextual information. We tested the hypothesis that thought disordered schizophrenics, unlike non-thought disordered schizophrenics, would present a deficit in the processing of the context during a task which involves these integrative processes. Methods. A group of 22 schizophrenic patients diagnosed in accordance with DSM-III-R criteria and a group of 11 control subjects were compared using a semantic priming version of the lexical decision task. The experimental design used low-level structuration of verbal material to reveal the difficulty that schizophrenic patients encounter in using semantic regularities. Results. A significant difference in priming effect was found between the three groups. Control subjects and non-thought disordered schizophrenics exhibit a priming effect for related word pairs when compared with unrelated pairs (respectively F(1,10) = 17.7; P < 0.002 and F(1,10)= 14.5; P > 0.003) but thought disordered schizophrenics did not (F(1,10) < 1; NS). Conclusions. This finding provides evidence for the cognitive heterogeneity of schizophrenic subjects. This absence of priming effect in thought-disordered schizophrenic subjects supports the hypothesis that these patients present a deficit in the post-lexical controlled information processing that permits the integration of semantic information.