Differential activation of temporal cortex during sentence completion in schizophrenic patients with and without formal thought disorder

The neural correlates of processing linguistic context in schizophrenic pat ients with formal thought disorder (FTD) were examined. Six right-handed ma le patients with prominent 'positive' FTD were compared with six schizophre nic patients without FTD and seven volunteers, matched for cognitive and de mographic variables. Functional magnetic resonance imaging (IMRI) was used to measure cerebral activation while subjects read and completed sentence s tems out loud. During a GENERATION condition, subjects were required to gen erate a word which completed the sentence stem appropriately. During a DECI SION condition, subjects selected and articulated one of two presented term inal words. A READING condition served as baseline. The three conditions we re compared with each other. Regions activated were identified in each grou p, and between-group differences were detected using an ANCOVA. When GENERA TION was compared with READING, FTD patients showed less activation in the right superior temporal gyrus than patients without FTD or controls, but gr eater activation in the left inferior frontal, inferior temporal and fusifo rm gyri. FTD patients also showed an attenuated right temporal response whe n GENERATION was compared with DECISION. This differential engagement of th e right temporal cortex was independent of differences in the speed or accu racy of responses, whereas the left fronto-temporal differences in activati on were not evident after covarying for task errors. The attenuated engagem ent of right temporal cortex, which is implicated in language comprehension at the discourse level, is consistent with neuropsychological evidence lin king thought disorder with deficits in processing linguistic context. (C) 2 001 Elsevier Science B.V, All rights reserved.