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

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-though disordered schizophrenics, would present a deficit in the processing of the context during a task which involves these integrative processes.

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.

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).

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.