Figure 4.

Stimulus–reward encoding within OFC and MFC during learning. A, Spike-density function and raster plot depicting the activity of a neuron recorded from OFC. The neuron exhibits the highest firing rate for stimuli associated with the greatest amount of reward and the lowest firing rate for stimuli associated with smallest amount of reward. Raster plots are sorted and color coded by the amount of reward associated with each stimulus. B, Mean (±SEM) activity of the neuron in A to the three different stimuli during the S1 and S2 periods relative to the start of the testing session. Mean responses are based on a running average of five trials. Yellow dots mark bins in which p < 0.05, FDR corrected. Inset shows trial-by-trial reward amounts associated with the three stimuli estimated from a reinforcement learning model fit to the data. C, Percentage of neurons classified by a sliding hierarchical ANOVA as encoding a factor during either the reference period (“Ref”, 1.0 s before the onset of the first stimulus), the S1 period (the initial 1.0 s after the onset of the first stimulus), or the S2 period (the initial 1.0 s after the onset of the second stimulus). D, Time course of encoding: mean (±SEM) percentage explained variance for neurons classified as encoding stimulus–reward associations in OFC (S1: dark blue; S2: cyan) and MFC (S1: red; S2: orange). Data are plotted relative to the onset of S1.