SENTENCE VERIFICATION AND DELUSIONS - A CONTENT-SPECIFIC DEFICIT

Background. A sentence verification task was developed to investigate semantic memory in schizophrenia. Methods. The test consisted of three types of sentence (true, unlikely and nonsense) and seven different t ypes of content (neutral, persecutory, grandiose, political, religious , relationships and somatic) representing common delusional themes pre sent in schizophrenic patients. Sixty-three schizophrenic patients and 66 matched control subjects were asked to make true/false judgements to 143 sentences. Results. Overall accuracy was similar across the two groups; sentences with some emotional themes and sentences of the unl ikely type produced the most violations. Significant differences betwe en the two subject groups were found specifically on nonsense sentence s with persecutory and religious themes. Patients made significantly m ore incorrect responses (acceptance) to nonsense sentences that had an emotional content congruent with their delusional beliefs, past or pr esent, and also on unlikely sentences (incorrect rejections) whose con tent was not congruent with their delusions. Further analysis of respo nse bias in the patients showed, overall, that there were more incorre ct rejections (a reflection of the large number of unlikely sentence e rrors) and more incorrect responses to sentences congruent with patien ts delusions. Furthermore, analysis of those patients currently experi encing delusions revealed more incorrect responses to sentences congru ent with their delusional ideas compared with patients not currently d eluded. Conclusions. These findings are indicative of cognitive bias i n schizophrenia towards certain emotional themes that may underlie ill ogical semantic connections and delusions.