The neural mechanisms of social reward in early psychosis.

Abstract

In chronic psychosis, reduced trust is associated with a neural insensitivity to social reward and reduced theory of mind (ToM). Here we investigate whether these mechanisms could underlie emerging social impairments in early psychosis. Twenty-two participants with early psychosis and 25 controls (male, 13–19 years) participated in two interactive trust games against a cooperative and unfair partner. Region of interest neuroimaging analyses included right caudate, medial prefrontal cortex (mPFC) and right temporoparietal junction (rTPJ), involved in reward and ToM processing. Both groups showed similar levels of trust (i.e. investments). However, individuals with psychosis failed to activate the caudate differentially in response to cooperation and unfairness while making decisions to trust. During cooperative returns, patients showed reduced and controls increased caudate activation. Patients demonstrated greater rTPJ activation than controls, possibly pointing towards compensatory mechanisms. Effects were associated with Wechsler Abbreviated Scale of Intelligence vocabulary scores. No group differences emerged in mPFC activation. Early psychosis is associated with an aberrant neural sensitivity to social reward. This could foster reduced social motivation and social isolation. Absent behavioural differences in early, relative to chronic psychosis could indicate that trust is achieved through increased compensatory demand on ToM.