Language and Mind

Abstract

Despite extensive research, the picture of lexical-semantic deficits in schizophrenia remains to be illuminated. Furthermore, research in first- episode psychosis with schizophrenia features/symptoms is lacking. By using the verbal fluency paradigm, it has recently been proposed that lexical-semantic deficits in schizophrenia might be caused by increased neural noise, resulting in stronger competition during lexical selection. The study recruited 22 first-episode psychosis (FEP) patients diagnosed with an acute schizophrenia- like psychotic disorder or acute polymorphic psychotic disorder with symptoms of schizophrenia according to ICD-10 criteria and 22 matched control subjects. Subjects were administered the category fluency task using two lexical-semantic categories: animals and trees. We hypothesized that (1) the patients would produce significantly fewer clustered words and significantly smaller clusters compared to control subjects and that (2) the patients would have a significantly higher switching score compared to control subjects. Our hypotheses were confirmed only in the animal fluency task, while no differences were observed in tree fluency. Our results indicate that there are disproportionate deficits in the animal and tree fluency tasks. FEP patients produced significantly fewer clustered words and significantly smaller clusters while also having a significantly higher switching score compared to HS in animal fluency, implying that FEP patients had difficulties in maintaining attention to a particular lexical-semantic subcategory. Furthermore, our results suggest that neural noise possibly depends on the automaticity of links between concepts in the given lexical- semantic category. Our results also show that FEP patients display dysfunctional connectivity in the mental lexicon.