210 Figure 4. LRTC of beta and gamma oscillations differentiate nocebo pain from high pain at baseline. Spatial topographies show the mean difference NoceboEvocation - BaselineHighPain for all subjects (n = 33; a-d) Relative power of alpha oscillations was significantly higher, whereas relative power of gamma oscillations was significantly lower, during nocebo pain, compared to high pain at baseline. (e-h) DFA of alpha oscillations was significantly higher above frontal and parietal areas. DFA of beta and gamma oscillations – in particular above frontal regions – was significantly lower during nocebo pain compared to high pain at baseline. Open white circles show statistical significance at P < .05. Closed white circles indicate significance after correcting for multiple comparisons (FDR) with q = 0.05, per topography. All boxplots show the mean across all electrodes. Table 1. Summary of statistics for differences in EEG parameters (nocebo/control) conditioning (Figure 2). EEG parameter Electrode MdnCONT MdnNOC Z p Relative power alpha WBA 17.2 ± 1.77 17.04 ± 1.58 1.75 0.08 PO3 24.88 ± 2.36 19.53 ± 2.12 2.73 0.0064 Relative power beta WBA 17.86 ± 1.13 18.55 ± 1.07 -0.20 0.84 Cz 15.42 ± 1.60 14.6 ± 1.56 3.05 0.0023 Relative power gamma WBA 6.99 ± 0.75 7.33 ± 0.70 -1.53 0.13 DFA alpha WBA 0.69 ± 0.01 0.68 ± 0.01 -0.35 0.73 DFA beta WBA 0.68 ± 0.01 0.69 ± 0.01 -0.79 0.43 DFA gamma WBA 0.69 ± 0.01 0.69 ± 0.01 -1.43 0.15 Note: Rows show EEG parameters, columns show the median whole-brain average value across subjects for control and nocebo trials, Z- and P-value corresponding to the signedrank test. The median EEG parameter value for each group is reported with the SE.
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