No evidence for left superior temporal dysfunction in asymptomatic schizophrenia and bipolar disorder - PET study of verbal fluency

Background Positron emission tomography (PET) studies have revealed functio nal left superior temporal gyrus (STG) abnormalities in symptomatic schizop hrenia during word generation. Aims To discover if this dysfunction is present in asymptomatic schizophren ia. To determine whether, without concurrent symptomatology, schizophrenia and bipolar affective disorder (BPD) are distinguishable by differing regio nal cerebral blood flow (rCBF) patterns during word generation. Method A PET verbal fluency protocol was applied to six patients with BPD i n remission and six patients with asymptomatic schizophrenia. Analysis incl uded 10 control subjects from a contemporaneous study. Results All groups showed relative reduction of rCBF in both superior tempo ral cortices. There were no quantitative differences in any group compariso n. All groups exhibited negative covariation between rCBF in left prefronta l and right (but not left) temporal regions. Conclusions Abnormal patterns of left STG function cannot be regarded as a trait marker for schizophrenia. Functional abnormalities may reflect aspect s of mental state. Declaration of interest Project funded by the Wellcome Trust.