Figure 7.

Comparison of reward encoding by individual neurons across tasks with familiar and novel stimuli. A, B, Spike-density functions, waveform plots, and raster plots depicting the activity of two neurons recorded within OFC in a familiar (top; Rudebeck et al., 2013a) and novel task (bottom; present study). The neuron in A increases its firing rate to stimuli associated with greater amount of reward in the familiar task, but a similar modulation by stimulus reward amount is not apparent in the task in which novel stimulus–reward associations have to be learned. The neuron in B has a higher firing rate when the monkey expects and then receives smaller amounts of reward in the familiar task, but has the opposite encoding in the novel task, where higher firing rates are associated with larger amounts of expected and received reward. C, Percentage of neurons that encode the amount of reward associated with S1, S2, expected, and received reward in the familiar task (blue) and the proportion of those neurons that also signal the same task factors in the novel task (red). Only neurons recorded in both tasks contributed to these plots and numbers in yellow give the overall percentages that encoded in both tasks relative to the familiar task.