Fig 1.
Participants were informed that the cue just preceding the pain was predictive of the upcoming pain. However, they were not informed about the occurrence or intensity of the ambiguous stimulus. All stimuli were followed by a numerical pain scale that was displayed for 6 seconds.
Fig 2.
The pain scale.
Fig 3.
Pain ratings for medium-intensity stimuli were the highest in the negative expectancy condition and lowest in the positive expectancy condition. Pain ratings in the prior expectancy condition were slightly lower than the control condition. *** p<0.001.
Table 1.
Post hoc comparisons for the different expectancy conditions.
Fig 4.
N2 magnitude differences between positive and prior negative expectancy conditions.
Averaged LEP peak amplitude across all participants are displayed. Nine electrodes (FC1, FCz, FC2, C1, Cz, C2, CP1, CPz, CP2) were pooled around the central Cz to produce an average for each of the N2 and P2 peak potentials. The LEP in the positive expectancy condition is displayed in black. The LEP in the prior negative expectancy condition is displayed in red.
Fig 5.
Source analysis contrasts following a paired t-test of N2 peak between the prior negative expectancy condition and the positive expectancy condition revealed activation of MCC at corrected significance threshold of p < 0.05.
Fig 6.
Scatterplot and linear least-squares line showing the correlation between the prior negative expectancy effect on N2 amplitude (prior negative expectancy condition minus positive expectancy condition) and the scores of the Fear of Pain Questionnaire (FPQ).