The study by Tobler, Fiorillo, and Schultz investigates how dopamine neurons adapt to the information provided by reward-predicting stimuli, which is crucial for animals to accurately estimate reward values. They found that midbrain dopamine neurons rapidly adjust their responses to align with the expected reward value and to the variance of reward values, maintaining their sensitivity over a wide range of reward values. This adaptation helps in discriminating between more likely and less likely reward outcomes efficiently. The neurons' responses to reward-predicting stimuli increase monotonically with the expected reward value, and they also show sensitivity to both the magnitude and probability of rewards. In experiments with monkeys, dopamine neurons' activity increased with the reward value of unpredicted liquids, similar to responses to reward-predicting stimuli. The neurons' sensitivity or gain adapts to the discrepancy between actual and expected rewards, ensuring that they can robustly discriminate between the most probable outcomes regardless of their absolute difference in magnitude. This adaptation allows the brain to efficiently represent reward values by focusing on probable values while discarding improbable ones, enhancing the efficiency and accuracy of neural coding.The study by Tobler, Fiorillo, and Schultz investigates how dopamine neurons adapt to the information provided by reward-predicting stimuli, which is crucial for animals to accurately estimate reward values. They found that midbrain dopamine neurons rapidly adjust their responses to align with the expected reward value and to the variance of reward values, maintaining their sensitivity over a wide range of reward values. This adaptation helps in discriminating between more likely and less likely reward outcomes efficiently. The neurons' responses to reward-predicting stimuli increase monotonically with the expected reward value, and they also show sensitivity to both the magnitude and probability of rewards. In experiments with monkeys, dopamine neurons' activity increased with the reward value of unpredicted liquids, similar to responses to reward-predicting stimuli. The neurons' sensitivity or gain adapts to the discrepancy between actual and expected rewards, ensuring that they can robustly discriminate between the most probable outcomes regardless of their absolute difference in magnitude. This adaptation allows the brain to efficiently represent reward values by focusing on probable values while discarding improbable ones, enhancing the efficiency and accuracy of neural coding.