208 power varying across frequency. Long-range temporal correlations were quantified using Detrended Fluctuation Analysis (DFA), which measures autocorrelations within a signal over time. (b) Power spectral density (PSD) was computed using Welch’s method with a Hamming window and a frequency resolution of 0.125 Hz. Frequency bands were defined as alpha (8–13 Hz), beta (13–30 Hz) and gamma (30–45 Hz). (c) Mean PSD of control (grey line, n = 34) and nocebo trials (blue line, n = 34) plotted in log-log scale. Wilcoxon signed-rank test was used to test for statistical significance between control and nocebo trials, per frequency bin. Black bars indicate frequency bins with P < .05. Shaded areas indicate standard error of the mean. (d-f) Difference in relative power alpha (d), beta (e) and gamma band (f) for nocebo minus control trials, mean of all subjects. 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. (g) Boxplots for relative power alpha. (h-j) Difference in DFA (h), beta (i) and gamma band (j) for nocebo minus control, mean of all subjects. (k) Boxplots for DFA. LRTC and alpha power differentiate nocebo pain from pain at baseline Our next question was whether these differences in and associations with LRTC of beta and gamma oscillations were present only during rest or if they also reflected nocebo hyperalgesia. To this end, Wilcoxon signed-rank tests were used to compare power and DFA of high pain at baseline EEG measurement with nocebo trials during the evocation phase. (Fig. 4, Table 2). Compared to baseline high pain, relative power within the alpha band was significantly higher during nocebo pain (Z = -3.5, p = 0.0004) (Fig. 4a). Relative power of gamma oscillations was lower during nocebo pain than during baseline high pain (Z = 3.3, p = 0.001) (Fig. 4c). Relative power within the beta band was not significantly different between nocebo during evocation and baseline high pain (Z = 0.5, p = 0.61) (Fig. 4b). DFA was higher during nocebo pain than during baseline high pain for alpha oscillations above frontal and parietal regions, however, not significant after FDR-correction and not significant for the whole-brain average (Z = -1.31, p = 0.19) (Fig. 4g). DFA was lower during nocebo pain than during baseline high pain for beta (Z = 3.14, p = 0.002) and gamma band (Z = 3.76, p = 0.0002) (Fig. 4h-i). These results indicate that power within the alpha band was
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