Reward Learning in Euthymic Patients with Bipolar Disorder Using a Probabilistic Reward Task / 대한정신약물학회지

OBJECTIVE: Bipolar disorder patients often show excessive goal-directed and pleasure-seeking behavior during manic episodes and reduced hedonic capacity during depressive episodes, indicating that bipolar disorder might involve altered reward processing. As such, bipolar disorder subjects have been reported to show impaired reward learning in situations requiring integration of reinforcements over time. In this study, we examined characteristics of reward learning in euthymic patients with bipolar disorder using a probabilistic reward task. METHODS: We recruited 23 euthymic patients with bipolar disorder and 47 healthy subjects for the probabilistic reward task. This task is a reward-based paradigm to produce a response bias, in which correct identifications of two ambiguous stimuli are differently rewarded. The other dependent measures were the discriminability, hit rate and reaction time. RESULTS: Relative to comparison subjects, bipolar patients showed a reduced acquisition of response bias toward the more frequently rewarded stimulus (p<0.01). The overall reward learning was positively correlated with state and trait anxiety levels in bipolar patients (p<0.01). No significant differences of discriminability, hit rates, and reaction time were found between bipolar patients and controls. CONCLUSION: These findings suggest that euthymic patients with bipolar disorder may have deficits in reward learning related to anxiety.

The Characteristics of Associative Learning of Reward Approach and Loss Aversion in Schizophrenia / 대한정신분열병학회지

OBJECTIVES: Schizophrenia patients have deficits of prediction and learning related to dopaminergic dysfunction. It is hypothesized that there would be different characteristics in associative learning of reward approach and loss aversion between controls and patients. METHODS: Participants were 23 healthy participants and 20 out-patients fulfilling criteria for schizophrenia according DSM-IV-TR. Using a monetary incentive contingency reversal task, successful learning rates, numbers of trials and errors till learning, numbers of trials of maintaining learning, response times were measured. Characteristics of learning were compared between controls and patients. RESULTS: Physical anhedonia and PANSS negative symptom scores correlated with the number of trials while loss aversion was maintained. Overall correct response rates were decreased in patient group, particularly during reward approach learning. Patients required more trials and errors to learn reward approach than controls. There were no significant differences in learning performance and reaction times between groups during loss avoidance learning. CONCLUSION: These results support previous reports of deficits in reward-driven learning in schizophrenia. However, anhedonia and negative symptoms were associated with the preserved function of loss avoidance learning.