THE NEURAL CORRELATES OF INNER SPEECH AND AUDITORY VERBAL IMAGERY IN SCHIZOPHRENIA - RELATIONSHIP TO AUDITORY VERBAL HALLUCINATIONS

Background. Auditory verbal hallucinations are thought to arise from t he disordered monitoring of inner speech (thinking in words). We teste d the hypothesis that a predisposition to verbal auditory hallucinatio ns would be associated with an abnormal pattern of brain activation du ring tasks which involved the generation and monitoring of inner speec h. Method. The neural correlates of tasks which engaged inner speech a nd auditory verbal imagery were examined using positron emission tomog raphy in (a) schizophrenic patients with a strong predisposition to au ditory verbal hallucinations (hallucinators), (b) schizophrenic patien ts with no history of hallucinations (nonhallucinators), and (c) norma l controls. Results. There were few between-group differences in activ ation during the inner speech task. However, when imagining sentences spoken in another person's voice, which entails the monitoring of inne r speech, hallucinators showed reduced activation in the left middle t emporal gyrus and the rostral supplementary motor area, regions which were strongly activated by both normal subjects and nonhallucinators ( p<0.001). Conversely, when nonhallucinators imagined speech, they diff ered from both hallucinators and controls in showing reduced activatio n in the right parietal operculum. Conclusions. A predisposition to ve rbal hallucinations in schizophrenia is associated with a failure to a ctivate areas implicated in the normal monitoring of inner speech, whe reas the absence of a history of hallucinations may be linked to reduc ed activation in an area concerned with verbal prosody.