Euthymic patients with bipolar disorder show decreased reward learning in a probabilistic reward task

Area of Science:

• Neuroscience
• Psychiatry
• Behavioral Science

Background:

• Bipolar disorder (BPD) involves mood swings from depression to mania, with altered reward processing suggested by behavioral changes.
• Manic phases show excessive goal-seeking, while depressive phases exhibit reduced pleasure, pointing to reward system dysregulation.

Purpose of the Study:

• To investigate if bipolar disorder (BPD) is characterized by impaired behavioral adjustment based on reinforcement history.
• To specifically examine reward processing in euthymic BPD individuals, assessing the impact of residual anhedonic symptoms.

Main Methods:

• A probabilistic reward task was administered to medicated BPD subjects and comparison subjects.
• Signal-detection analysis assessed response bias to measure behavioral adaptation to reinforcement history in euthymic BPD patients.

Main Results:

• Euthymic BPD subjects demonstrated delayed and reduced acquisition of response bias towards more rewarded stimuli.
• Increased sensitivity to disadvantageous stimuli and correlation between reduced reward learning and anhedonia were observed in the BPD group.

Conclusions:

• BPD, even in euthymic states, shows dysfunctional reward learning, particularly in integrating reinforcement over time.
• This suggests a potential neural basis for altered reward processing in bipolar disorder.