Dysfunction of the social brain in schizophrenia is modulated by intention type: an fMRI study

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.

Fig. 1

Activation paradigm, exemplarily shown for a trial of the CInt condition.

Fig. 2

Main effects for the three experimental conditions (PInt, PSInt, CInt) versus control condition (Ph-C) within-groups (Analysis of Model 1). Second level ANOVA, P < 0.05 FDR corrected.

Fig. 3

Regions in which healthy controls showed relatively more cerebral activation compared with paranoid patients for the three experimental conditions (PInt, PSInt, CInt) versus control condition (Ph-C). Second level ANOVA, P < 0.001 uncorrected, P < 0.05 at the cluster level. For location within the MNI-template compare Figure 4.

Fig. 4

Regions from Figure 3 shown in the MNI template.

Fig. 5

Mean activation effects (estimated beta parameters, 95% confidence interval) of the contrast Cint vs PhC for right TPJ, MPFC and left TPJ. The activation effects were extracted from the second level between-group ANOVA, P < 0.001 uncorrected, P < 0.05 at the cluster level. Red: Healthy control subjects; Blue: Paranoid patients. Dashed circles indicate the beta parameters for the control condition (Ph-C).