Abstract
Background: Human beings are tuned for social stimuli. This tendency for individuals to prioritize processing social over nonsocial stimuli is referred to as social preference. Various lines of evidence emerging from basic science support the crucial role of social preference in the development of social cognitive skills and social functioning. It is plausible that disrupted social preference may play a role in social cognitive impairment and social dysfunction in schizophrenia. Hence, this study focused on one aspect of social preference, social reward, and examined its neural correlates in schizophrenia using a functional magnetic resonance imaging (fMRI).
Methods: Twenty-five outpatients with schizophrenia and 25 demographically matched community controls participated in this study. To assess sensitivity to social reward vs. nonsocial reward, a one-armed bandit task was administered in the 3T scanner at UCLA. At each trial, two slot machines appeared and subjects were asked to choose the slot machine that would give them the optimal outcome. For the social reward, faces showing happy, angry or neural emotional expressions were used. For nonsocial reward, an image of a dollar bill or an image of a dollar bill crossed out was used.
Results: Based on previous studies, we focused on two regions of interest (ROIs), the ventral striatum (VS) and ventromedial prefrontal cortex (vmPFC). In the VS, compared to controls, schizophrenia patients showed reduced neural activation for social reward. However, two groups showed comparable levels of neural activation for nonsocial reward. Similarly, in the vmPFC, compared to controls, patients showed reduced neural activation for social reward but not for nonsocial reward.
Conclusion: Our study found blunted neural activation of schizophrenia patients in the VS and vmPFC when processing social reward not but for nonsocial reward. Neural circuits for reward processing appear not to show sensitivity to social reward in schizophrenia, suggesting aberrant neural processes associated with disrupted social preference in schizophrenia.