Objective: Poor social functioning is a hallmark of schizophrenia and may precede the onset of illness. One of the most robust predictors of social impairment is a deficit in the ability to appreciate the mental states of others ("theory of mind"; ToM). We therefore examined ToM in subjects at risk of developing psychosis using an fMRI paradigm and compared brain activations with those of patients with manifest schizophrenia and healthy controls.
Method: Ten subjects with at-risk ("prodromal") states of psychosis, 22 schizophrenia patients and 26 healthy controls were recruited. During fMRI scanning, participants were shown a series of cartoons. The task was to infer the mental states of the cartoon characters in terms of beliefs, states of knowledge and intentions.
Results: Subjects at risk of psychosis activated the ToM neural network comprising the prefrontal cortex, the posterior cingulate cortex, and the temporoparietal cortex more strongly than patients with manifest schizophrenia, and, in part, also more strongly than healthy controls. Manifest schizophrenia patients and controls activated the ToM neural network differently with little overlap of activated regions, where overall, controls showed stronger activations than schizophrenia patients.
Conclusions: Individuals with at-risk states of schizophrenia activate the ToM neural network differently, and in part, more strongly compared to patients with schizophrenia and controls. This could suggest a compensatory overactivation of brain regions critical for empathic responses during mental state attribution in at-risk subjects for schizophrenia.
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