Subjective value: dopamine neurons

At choice indifference between a safe reward and a gamble, the subjective reward value is equal for the two options, even when the mean physical amounts differ (left). The dopamine response is also equal, even when the amounts differ (right: dotted vs. solid lines). Despite their same responses, the neurons are sensitive to reward value, as their response increases with increasing value (right: different colours). Data from Stauffer et al. 2014.

Dopamine neuronal response

Economic utility formalises the subjective nature of reward value mathematically. Meaningful reward neurons should code utility rather than physical amount. The dopamine reward prediction error (RPE) signal follows nonlinear utility with unpredicted reward (left) and gambles (right: stronger dopamine UPE response at steeper utility slope despite same physical RPE). View the report here (Stauffer et al. 2014).