TY - JOUR T1 - Single-Cell and Population Coding of Expected Reward Probability in the Orbitofrontal Cortex of the Rat JF - The Journal of Neuroscience JO - J. Neurosci. SP - 8965 LP - 8976 DO - 10.1523/JNEUROSCI.0005-09.2009 VL - 29 IS - 28 AU - Esther van Duuren AU - Geoffrey van der Plasse AU - Jan Lankelma AU - Ruud N. J. M. A. Joosten AU - Matthijs G. P. Feenstra AU - Cyriel M. A. Pennartz Y1 - 2009/07/15 UR - http://www.jneurosci.org/content/29/28/8965.abstract N2 - The orbitofrontal cortex (OFC) has been implicated in decision-making under uncertainty, but it is unknown how information about the probability or uncertainty of future reward is coded by single orbitofrontal neurons and ensembles. We recorded neuronal ensembles in rat OFC during an olfactory discrimination task in which different odor stimuli predicted different reward probabilities. Single-unit firing patterns correlated to the expected reward probability primarily within an immobile waiting period before reward delivery but also when the rat executed movements toward the reward site. During these pre-reward periods, a subset of OFC neurons was sensitive to differences in probability but only very rarely discriminated on the basis of reward uncertainty. In the reward period, neurons responded during presentation or omission of reward or during both types of outcome. At the population level, neurons were characterized by a wide divergence in firing-rate variability attributable to expected probability. A population analysis using template matching as reconstruction method indicated that OFC generates a distributed representation of reward probability with a weak dependence on neuronal group size. The analysis furthermore confirmed that predictive information coded by OFC populations was quantitatively related to reward probability, but not to uncertainty. ER -