No abstract

In this fMRI study, we investigated theory of mind (ToM) in patients with paranoid schizophrenia. We hypothesized that the network supporting the representation of intentions is dysfunctional in patients with schizophrenia dependent on the type of intention involved. We used a paradigm including a control condition (physical causation) and three intention conditions (private intention, prospective social intention and communicative intentions) differing in the degree of social interaction. In all four experimental conditions patients performed worse than controls regarding accuracy and reaction time. They showed significantly less activation in three regions typically activated in ToM tasks, i.e. paracingulate cortex and bilateral temporo-parietal junctions. However, this dysfunction was dependent on the type of intention represented, i.e. was present only for social but not for non-social intentions. Moreover, part of the reduced activation was related to the fact that there was no signal drop in these regions for the physical causality condition as usually found in controls. This may be due to the tendency of schizophrenic patients to attribute intentionality to physical objects. Our findings have implications for the study and understanding of ToM in schizophrenia but also in other disorders like autism.

Evidence from magnetic resonance imaging (MRI) suggests early structural and functional brain changes in individuals with the Huntington's disease (HD) gene mutation who are presymptomatic for the motor symptoms of the disorder (pre-HD subjects). The objective of this study was to investigate the functional neuroanatomy of verbal working memory (WM) in pre-HD subjects. By means of event-related functional MRI, we studied healthy controls (n = 16) and pre-HD subjects (n = 16) with a parametric WM paradigm comprising three different WM load levels. Voxel-based morphometry (VBM) was used to control potentially confounding brain atrophy. Although WM performance did not significantly differ between pre-HD subjects and healthy controls, pre-HD subjects showed a significantly decreased activation of the left dorsolateral prefrontal cortex (DLPFC) at intermediate and high WM load levels only. This region was not affected by early cortical atrophy, as revealed by VBM. Pre-HD individuals close to the onset of motor symptoms showed an increased activation of the left inferior parietal lobule and the right superior frontal gyrus compared with both pre-HD subjects far from symptom onset and healthy controls. In addition, the activation level in the left DLPFC was positively correlated with the UHDRS cognitive subscore in pre-HD subjects. Our findings demonstrate that early functional brain changes in pre-HD subjects may occur in the DLPFC before manifest cortical atrophy, and support a role of this region in the expression of clinical symptoms. Compensatory brain responses in pre-HD individuals may occur with closer proximity to the onset of manifest clinical symptoms.