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. 2020 Jan 22;105(2):370–384.e8. doi: 10.1016/j.neuron.2019.10.030

Figure 6.

Figure 6

Mediation Analysis Can Explain the Relationship between Reward Magnitude and actTime

(A) Mediation occurs when the direct effect of contextual factors on actTime (path c) can be explained by an indirect pathway through a brain area (path a × b).

(B) The ACC mediated the quadratic relationship between reward magnitude and actTime. This was not the case for plBF or amBF or between other elements among contextual factors. However, after controlling for the effect of reward magnitude on the current trial, we found a small mediation effect of the ACC for the influence of past reward on actTime (bootstrapped p = 0.06). The numbers are the coefficients of each path. Significant paths are displayed with thick arrows.

(C) PPI analysis between the BOLD signal in the ACC and plBF (top panel) and amBF (bottom panel), with quadratic reward magnitude as the psychological factor. Trial-by-trial variation in the activity in the ACC was more strongly related with trial-by-trial variation in the activity in the plBF as a function of reward magnitude compared with the amBF (Wilcoxon signed-rank test; Z = 2.11, p = 0.035, r = 0.22).