In order to determine those brain areas that covaried with the SPE, we pooled across both sessions and found significant effects bilaterally in the posterior intraparietal sulcus (pIPS) reaching on the left side into the superior parietal lobule and on the right side into the angular gyrus, and in the lateral prefrontal cortex (latPFC) (dorsal bank of the posterior inferior frontal gyrus (pIFG), see circled areas in Figure 3a and 3b and Table 2). Other effects visible in Figure 3a (e.g. inferior temporal gyrus) did not meet our statistical threshold for whole-brain correction and are not further discussed. The graphs show the average percent signal change (PSC) in BOLD activation across subjects for both prediction error signals on trials in which that error signal was either low, medium or high (bins defined at 33rd, 66th, and 100th percentile, see Experimental Procedures for details). This reveals a linear increase in BOLD activation across trials with increasing SPEs, except for the left IPS, in which the increase in BOLD activation occurs only for trials with the highest SPE. In contrast, there is no such systematic relationship between BOLD activation and the RPE.
