Figure 1.

Task and recording locations. A, Structure of an individual trial in the three-arm bandit task where monkeys indicated their choice by making a saccade to one of three options. Following each choice, the monkeys received either a fixed amount of juice reward with a probability conditioned on the stimulus or no reward. B, Each block of 650 trials began with the presentation of three novel images. This set, s, of visual choice options was repeatedly presented to the monkey for a series of 10–30 trials. On a randomly selected trial between 10 and 30 one of the existing options was randomly selected and replaced with a novel image. This formed a new set of options that were presented for a series of 10–30 trials. Novel options were randomly assigned their own reward probabilities (0.2, 0.5, 0.8). Configurations in which all three options had the same reward probability were not allowed. This process of introducing a novel option to create a new set was repeated 32 times within a block. C, MRI guided reconstruction of recording locations. Coronal T1-weighted MRI of electrodes lowered to specific depths for neuroimaging, were used to verify the trajectories and placement of the recording electrodes in each monkey. The number of cells recorded in the OFC at each site were projected on to template views from a standard macaque brain atlas.