Value coding by primate amygdala neurons complies with the continuity axiom of economic choice theory

The primate amygdala contributes to decision-making by encoding the subjective value of rewards, but whether these signals align with principles of economic theory remains unclear. Here, we tested compliance of amygdala value coding with the continuity axiom of expected utility theory (EUT), which posits a trade-off between reward probability and magnitude, in two male macaques. Given three ranked gambles, axiom-compliance was assessed via the monkeys' behavioral indifference between the intermediate gamble and a probabilistic combination of the other two. Choices reflected probability-magnitude integration to scalar subjective values consistent with the axiom. In a nonchoice task, amygdala neurons showed graded responses to probability and magnitude cues that reflected these individual preferences, equalizing at subjective indifference. During choice, amygdala neurons directly integrated these value components and translated them into chosen-value and choice signals. These findings demonstrate that amygdala neurons represent behaviorally relevant, preference-based values in accordance with EUT's continuity axiom, and contribute to translating these values into economic decisions.<b>NEW & NOTEWORTHY</b> The amygdala-long associated with emotional responses-has recently been implicated in economic decision-making. Here, we show that primate amygdala neurons respond to visual cues indicating reward probability and magnitude in a manner that reflects the integration of these variables into subjective values. These value signals complied with the notion that decision makers maximize the value of rewards, formalized by key axioms of economic theory. Beyond valuation, some neurons processed subjective values into choice-predictive signals.