This study investigates the role of dopamine in human reward-seeking behavior, focusing on how dopamine-dependent prediction errors in the striatum influence decision-making. The research used a combination of behavioral, pharmacological, computational, and functional magnetic resonance imaging (fMRI) techniques to examine the effects of dopamine-modulating drugs on brain activity and behavior in healthy subjects. The results show that during instrumental learning, the magnitude of reward prediction errors expressed in the striatum is modulated by the administration of drugs that enhance (L-DOPA) or reduce (haloperidol) dopaminergic function. Subjects treated with L-DOPA showed a greater tendency to choose the most rewarding action compared to those treated with haloperidol. Furthermore, incorporating the magnitude of prediction errors into a standard action-value learning algorithm accurately reproduced subjects' behavioral choices under different drug conditions. The study also found that dopamine-dependent modulation of striatal activity is crucial for how the human brain uses reward prediction errors to improve future decisions. Dopamine is closely associated with reward-seeking behaviors, such as approach, consummation, and addiction. The research demonstrates that dopamine neurons encode reward prediction errors, which are essential for learning and decision-making. The findings suggest that dopamine modulates the apparent value of rewards as represented in the striatum, and that this process is critical for reward-seeking behavior. The study also highlights the distinct roles of different striatal regions in reward and aversive prediction errors, and provides insights into the mechanisms underlying dopamine's role in reward and aversive learning. The results have implications for understanding clinical disorders where dopamine is implicated, such as Parkinson's disease and schizophrenia.This study investigates the role of dopamine in human reward-seeking behavior, focusing on how dopamine-dependent prediction errors in the striatum influence decision-making. The research used a combination of behavioral, pharmacological, computational, and functional magnetic resonance imaging (fMRI) techniques to examine the effects of dopamine-modulating drugs on brain activity and behavior in healthy subjects. The results show that during instrumental learning, the magnitude of reward prediction errors expressed in the striatum is modulated by the administration of drugs that enhance (L-DOPA) or reduce (haloperidol) dopaminergic function. Subjects treated with L-DOPA showed a greater tendency to choose the most rewarding action compared to those treated with haloperidol. Furthermore, incorporating the magnitude of prediction errors into a standard action-value learning algorithm accurately reproduced subjects' behavioral choices under different drug conditions. The study also found that dopamine-dependent modulation of striatal activity is crucial for how the human brain uses reward prediction errors to improve future decisions. Dopamine is closely associated with reward-seeking behaviors, such as approach, consummation, and addiction. The research demonstrates that dopamine neurons encode reward prediction errors, which are essential for learning and decision-making. The findings suggest that dopamine modulates the apparent value of rewards as represented in the striatum, and that this process is critical for reward-seeking behavior. The study also highlights the distinct roles of different striatal regions in reward and aversive prediction errors, and provides insights into the mechanisms underlying dopamine's role in reward and aversive learning. The results have implications for understanding clinical disorders where dopamine is implicated, such as Parkinson's disease and schizophrenia.