Reward learning impairment in patients with first-episode schizophrenia-spectrum disorder

Abstract

BACKGROUND: Accumulating evidence indicated that schizophrenia patients exhibited reward learning impairment. Nonetheless, most previous studies focused on chronically-ill patients who had longstanding exposure to antipsychotic medication treatment which may interfere with reward processing. In this study, we aimed to investigate reward learning impairment (gradual reinforcement learning) in patients with first-episode schizophrenia-spectrum disorder with particular focus on its relationship with a key negative symptom sub-domain, namely avolition. METHODS: Thirty-one patients with first-episode DSM-IV schizophrenia, schizophreniform disorder or schizoaffective disorder (treated with antipsychotic for 3-6 months) and 33 healthy controls matched with age, sex and educational level were recruited. Each subject completed a computerized Go/No Go task, in which they had to decide whether or not to choose each stimulus which had different reinforcement probabilities. The task comprised 3 training blocks and 1 transfer phase presenting novel combinations of previously learned stimuli. A battery of cognitive assessments was administered to patients and HC. Patients were assessed with symptom severity using PANSS and SANS (for negative symptoms). Data on antipsychotic medication treatment was obtained. Omnibus repeated measures ANOVA and one-way ANOVAs were used to compare gradual reinforcement learning performance of patients and HC. Spearman’s correlational analyses were used to examine the association between reinforcement learning deficit and symptom dimensions. RESULTS: Patients did not differ from HC in terms of age (P: mean: 24.81, SD: 7.42; HC: mean: 23.68, SD: 7.49), sex (P: male: 42%; HC: male:47%) and years of education (P: mean: 12.48, SD: 2.67; HC: mean: 12.70, SD: 2.73). HC had significantly higher IQ estimate and better overall cognitive functions than patients. Regarding gradual reinforcement learning performance, patients had significantly lower accuracy in positive stimuli in training blocks 2 (F(1,62) = 6.25, p<0.05) and 3 (F(1,62) = 8.00, P<0.05). Patients also had longer reaction time to positive stimuli in training blocks 2 (F(1,62) = 9.22, P<0.05) and 3 (F(1,62) = 4.70, P<0.05). Avolition score (derived from Avolition-Asociality global sum score of SANS) negatively correlated with positive stimuli’s accuracy in transfer phase (r(31)=−0.48, p<0.01). DISCUSSION: The findings of this study indicated that gradual reinforcement learning deficit (esp. positive reinforcement dysfunction) was found in the initial stage of schizophrenia and was associated with severity of volitional impairment. Further prospective research is required to clarify longitudinal course of reward leaning impairment and its relationship with outcome on symptoms and functioning.