238 Figure 3. Mean pain ratings are shown in pre-conditioning (Pre) baseline (Basel), nocebo induction (Indu), and extinction (Ext) including the first two extinction trials (Evocation) where behavioral nocebo effects were measured. D-cycloserine (DCS) administration did not significantly affect the magnitude of nocebo responses. The slight group difference in ratings observed indicates a minor average difference in individually calibrated pain intensities and had no significant effects on outcomes. fMRI results Increased activity in evocation nocebo trials compared to baseline high pain was found in the right operculum (Table 2, Figure 4A). During the acquisition phase, we detected an increased BOLD response during nocebo trials in bilateral ACC, bilateral amygdala, bilateral insula, and bilateral vlPFC (all clusters from a priori analyses are presented in Table 2, Figure 4B, Figure 5A-C). No clusters reached the threshold for significance in the evocation (first 10 extinction trials) control and nocebo contrast initially, but notably, in exploratory analyses of the evocation phase with no minimum cluster size, we detected an increased BOLD response during nocebo trials in the left insula (all clusters from exploratory findings in Table 3, Figure 4C), albeit this did not reach significance. Exploratory analysis of the remaining 18 extinction trials detected increased BOLD signal during
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