Reduced Neural Sensitivity to Social vs Nonsocial Reward in Schizophrenia

Abstract

Background: Human beings find social stimuli rewarding, which is thought to facilitate efficient social functioning. Although reward processing has been extensively studied in schizophrenia, a few studies have examined neural processes specifically involved in social reward processing. This study examined neural sensitivity to social and nonsocial rewards in schizophrenia.

Methods: Twenty-seven patients with schizophrenia and 25 community controls completed a One-Armed Bandit Task, an implicit reinforcement learning task, in the scanner. There were 2 conditions with an identical trial structure, one with social rewards and the other with nonsocial rewards. The data were analyzed using a region of interest (ROI) approach, focusing on the ventral striatum, ventromedial prefrontal cortex, and anterior cingulate cortex.

Results: Across all 3 ROIs, patients showed reduced activation for social rewards compared to controls. However, the 2 groups showed comparable levels of activation for nonsocial rewards. Within the patient group, levels of neural activation in these ROIs during the social reward condition were associated with better performance.

Conclusions: This study found reduced neural sensitivity in patients with schizophrenia in key reward-processing regions for social but not for nonsocial rewards. These findings suggest a relatively specific social reward-processing deficit in schizophrenia during an implicit reinforcement learning task.

Keywords: anterior cingulate cortex; schizophrenia; social motivation; social preference; social reward; ventral striatum; ventromedial prefrontal cortex.

Fig. 1.

A schematic diagram of the One-Armed Bandit Task. (A) There are 3 types of slot machines. A “good” slot machine had an 80% probability of a positive outcome and a 20% probability of neutral outcome; a “bad” slot machine had an 80% probability of negative outcome and a 20% probability of neutral outcome; and a “neutral” slot machine had a one-third probability of each positive, neutral, and negative outcomes. (B) Each reward condition with an identical trial structure consisted of 2 trial types: a high-payout trial and a low-payout trial. For the high-payout trial, a good slot machine was paired with a neutral slot machine. For the low-payout trial, a bad slot machine was paired with a neutral slot machine. The key contrast for sensitivity to reward for functional magnetic resonance imaging (fMRI) data was the contrast of high-payout vs low-payout trials for social and nonsocial reward conditions.

Fig. 2.

Neural sensitivity to social and nonsocial reward of patients with schizophrenia (SZ) and controls (CO) during the One-Armed Bandit Task in the ventral striatum (A), ventromedial prefrontal cortex (vmPFC, B), and anterior cingulate cortex (ACC, C). The y-axis represents neural sensitivity to social reward (ie, a contrast of high-payout trials vs low-payout trials).