Neurobiological Bases of Economic Choice Behavior

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Economic choice is the behavior observed when individuals make choices solely based on subjective preferences¿for example out of a restaurant menu. Choice behavior is a traditional focus in economics and psychology. However, economic choice is also critically important from a medical perspective, as choice deficits are often observed in patients with neurological disorders of the frontal lobe and in addiction. Behaviorally, evidence indicates that economic choice entails assigning values to the available options¿for example, to different items on the menu. The underlying neurobiological mechanisms remain, however, poorly understood. Evidence from lesions, functional imaging and electrophysiology suggest that the orbitofrontal cortex (OFC) may play an important role in economic choice. The overarching goal of this proposal is to examine the contribution of this cortical area in detail. This will be achieved by recording the activity of individual neurons in awake monkeys while they engage in economic choice tasks. In our experiments, monkeys choose between different beverages offered in variable amounts. Their choices provide a behavioral measure for the relative value of the two juices. Our preliminary studies indicate that neurons in OFC encode the value monkeys assign to offered and chosen juices, suggesting that choices are based upon the activity of this neuronal population. This observation raises several critical questions that will be addressed in the experiments proposed here. First, does the neuronal representation of value vary depending on the behavioral context? For example, the neuronal valuation system might adapt to the contextual value range to exploit maximal discriminatory power, in a way similar to how the visual system adapts to ambient light. Second, do OFC neurons encode economic utility or pure value? Choices are often made between options that involve risks and costs, both reflected in the expected utility. If choices are based on the activity of OFC, we expect neurons in this area to encode economic utility, as distinguished from pure value. Finally, in spite of a substantial literature on the anatomy of the frontal lobe, what areas receive anatomical projections from value-encoding neurons remains unclear. To address this issue, we will combine anatomical tracings with neurophysiological recordings. This study will also provide the PI an opportunity to learn histological and anatomical techniques that will complement his portfolio of expertise.