Figure 4.

dACC effects on reward rate mediated by self-report motivation ratings. A, Within-subjects mediation analysis of dACC. Three linear mixed-effects models were conducted to confirm the effects of incentive conditions in dACC, reward rate, and motivation ratings (see red dashed lines). The models revealed that incentive conditions significantly predicted dACC bundled β, reward rate, and motivation ratings. Next, a Bayesian multilevel within-subjects mediation analysis was conducted to test for a relationship between these three variables. The mediation analyses revealed that the relationship between within-subjects variability in dACC and reward rate was mediated by within-subjects variability in motivation ratings (see blue lines). Inclusion of motivation ratings partially mediated the association between dACC and reward rate proportion mediated effect = 0.42, CI₉₀ = (0.06, 1.10); 90% credible intervals are used as the range of the posterior distribution for each of the path parameters. ***p < 0.001. For parameter estimates, see Extended Data Figures 4-1 and 4-2. B, Between-subjects correlations of dACC. Left, Scatterplot of z-scored averaged dACC β estimates and reward rate by subject revealed an association between dACC and reward rate (though beneath threshold for statistical significance). Right, Scatterplot of z-scored averaged dACC β estimates and self-report motivation ratings also revealed association between dACC and motivation ratings.