Representation of the trial outcome ramped up following receipt of outcome information (Figure 3E), accompanied by an initially equally strong representation of the interaction between trial outcome and second-step state. This interaction indicates that the representation of trial outcome depended strongly on the state in which the outcome was received, and individual neurons which differentiated between reward and non-reward tended to do so only in one of the two second-step states (Figure S5). To assess this in more detail, we ran a version of the regression analysis with separate predictors for outcomes received at the left and right ports, and plotted the left and right outcome regression weights 250 ms after outcome against each other (Figure 3H). Representations of trial outcome obtained at the left and right ports were orthogonal (R2 = 0.0024), indicating that although ACC carried information about reward, reward representations were specific to the state where the reward was received.
