Primate anterior insular cortex represents economic decision variables postulated by Prospect theory

In humans, risk attitude is highly context-dependent, varying with wealth levels or for different potential outcomes, such as gains or losses. These behavioral effects are well described by Prospect Theory, with the key assumption that humans represent the value of each available option asymmetrically as gain or loss relative to a reference point. However, it remains unknown how these computations are implemented at the neuronal level. Using a new token gambling task, we found that macaques, like humans, change their risk attitude across wealth levels and gain/loss contexts. Neurons in their anterior insular cortex (AIC) encode the reference point (i.e. the current wealth level of the monkey) and the asymmetric value function (i.e. option value signals are more sensitive to change in the loss than in the gain context) as postulated by Prospect Theory. In addition, changes in the activity of a subgroup of AIC neurons are correlated with the inter-trial fluctuations in choice and risk attitude. Taken together, we find that the role of primate AIC in risky decision-making is to monitor contextual information used to guide the animals willingness to accept risk.