Manic and Depressive Phases: During manic phases, individuals with bipolar disorder exhibit inflexible and excessive seeking of rewards. Conversely, during depressive phases, they show a marked insensitivity to rewards. This suggests that the striatum's dysfunction contributes to the extreme fluctuations in reward-seeking behavior observed in bipolar disorder.

Circuitry and Adaptation: A neural circuit involving the prefrontal cortex, striatum, and amygdala is crucial for adapting to changing reward contingencies. Some researchers propose that abnormalities in this circuit lead to inflexible responses to rewards in individuals with bipolar disorder. This inflexibility can manifest as excessive reward-seeking during mania and a lack of reward-seeking during depression.