title: Coding of reward risk by orbitofrontal neurons is mostly distinct from coding of reward value.
abstract: Risky decision-making is altered in humans and animals with damage to the orbitofrontal cortex. However, the cellular function of the intact orbitofrontal cortex in processing information relevant for risky decisions is unknown. We recorded responses of single orbitofrontal neurons while monkeys viewed visual cues representing the key decision parameters, reward risk and value. Risk was defined as the mathematical variance of binary symmetric probability distributions of reward magnitudes; value was defined as non-risky reward magnitude. Monkeys displayed graded behavioral preferences for risky outcomes, as they did for value. A population of orbitofrontal neurons showed a distinctive risk signal: their cues and reward responses covaried monotonically with the variance of the different reward distributions without monotonically coding reward value. Furthermore, a small but statistically significant fraction of risk responses also coded reward value. These risk signals may provide physiological correlates for the role of the orbitofrontal cortex in risk processing.
authors.affiliation: Department of Physiology, Development, and Neuroscience, University of Cambridge, Downing Street, Cambridge CB23DY, UK. mo293@cam.ac.uk
authors.forename: Martin
authors.initials: M
authors.lastname: O'Neill
authors.forename: Wolfram
authors.initials: W
authors.lastname: Schultz
mesh_terms: D000818:Animals; D003657:Decision Making / Q000502:physiology*; D008253:Macaca mulatta; D008297:Male; D009474:Neurons / Q000502:physiology*; D010775:Photic Stimulation / Q000379:methods; D017397:Prefrontal Cortex / Q000502:physiology*; D012201:Reward; D012309:Risk-Taking