Mentalizing impairment in schizophrenia: a functional MRI study

Abstract

Background: A deficit in Theory of mind (ToM) or 'mentalizing' has been purported to underlie the poor social functioning seen in patients with schizophrenia. To understand the neural basis of this deficit studies have primarily used tasks requiring 'off-line' or explicit mentalizing but, in daily life, successful social interactions depend upon implicit or 'on-line' mentalizing. Therefore in the present study we used functional neuroimaging and a task that elicits 'on-line' mentalizing to investigate the neural basis of ToM deficits in schizophrenia.

Methods: Functional MRI images were acquired from 20 male patients with established schizophrenia and 19 age and gender matched healthy controls while they watched animated sequences involving two triangles. In the control condition the two triangles moved at random whereas in the experimental condition they moved interactively with implied intentions. The identification of ToM networks and differential responses between groups, within this network, was investigated using a random effects model. To account for differences in educational status between the groups this was included as a covariate in the between group analysis. Correlation analysis was performed to examine the relationship between neural activity change during mentalizing and the clinical and functional outcomes of patients.

Results: Patients with schizophrenia had significantly diminished activity in the right superior temporal gyrus (STG) at the temporoparietal junction (TPJ) and bilaterally within the inferior frontal gyri (IFG). Interestingly, frontal neural activity showed significant correlation with functional outcomes in patients with schizophrenia.

Conclusions: Findings from this novel study suggest that the ToM deficit in male schizophrenia patients may reflect impairment in the automatic or implicit processing of mentalizing. If replicated, this is an important finding that provides additional insight into the neural basis of impairments in social functioning that are experienced by patients with schizophrenia.