Abstract 

Although most functional and structural neuroimaging studies have reported that cognitive deficits in patients with schizophrenia are associated with prefrontal abnormalities, their findings vary considerably. The aim of this study is to find evidence of functional abnormalities in the prefrontal cortex of schizophrenia patients on the basis of exact topographical parcellation. Magnetic resonance (MR) images were obtained in 12 patients with schizophrenia and 12 age- and sex-matched normal volunteers, and parceled into 8 frontal subregions using topographic landmarks. [15O]H2O PET scans were obtained during the visual working memory task and the control task, and the activities of the parceled frontal subregions were counted on the registered PET images. In the comparison of the subregional functional activities, the normal healthy group showed a tendency t o activate the right rostral anterior cingulate during the working memory task. Comparatively, the patient group showed reduced activation of the right orbitofrontal cortex and the right caudal anterior cingulate. The results suggest that the functional c hanges observed in schizophrenia may result from the abnormal activation of the neural system for the purpose of performing working memory tasks. In particular, reduced ventromedial prefrontal activities seem to play an important role in such cognitive impairment in schizophrenia.