Overview of available datasets for each EEG session. Numbers reflect relevant datasets for Visit 1 / Visit 2.

Overview of the experimental paradigm and naming conventions throughout the paper. At Testing Visits 1 and 2, participants completed the progression of experimental sessions. Prior to Pain-Free 2 & 3, an icepack was applied to the stimulated forearm for three minutes (not shown in figure). Representative data reflects the average Visit 1 pain ratings from participants who responded to capsaicin (average CHP pain > 10). Instances where EEG sessions were separated into distinct datasets are denoted by the presence of different colors within the same panel. Naming conventions for all datasets are provided in the table and, where an EEG session was divided into multiple datasets, shading color in the table has been matched to the color provided in the data panels.

Peak Alpha Frequency (PAF) is slowed during two models of Prolonged Pain. A. Topoplot of the estimated effect of PHPOn on PAF. Cooler colors reflect that PAF decreased from Pain-free 1 to PHPOn while warmer colors indicate that PAF became faster. PHPOn PAF was found to be significantly slower than PAF recorded during Pain-Free 1 and from PAF recorded during PHPOff and Pain-free 2 with this effect being observed maximally at a left, frontocentral cluster (black dots with white outlines). B. Topoplot of the estimated effect of Visit 2 on PAF during PHP. Cooler colors reflect that PAF was slower during Visit 2 than during Visit 1. Visit 2 PAF was found to be significantly slower, which was maximally observed over (1) and left (3) occipital clusters as well as a right frontal cluster. C. Line plot (mean +/- SEM) depicting PAF estimates recorded from the C3 channel during Phasic Heat Pain. For ease of visualization, PAF estimates are presented as relative to Pain-Free 1. D. Topoplot of the average estimated effect of CHP, Pain-Free 3, and CHP Rekindle on PAF. PAF was found to be significantly slower during all three sessions at a bilateral maximally observed over a frontocentral cluster. E. Topoplot of the estimated effect of Visit 2 on PAF during CHP. No significant clusters associated with the effect of Visit were identified. F. Line plot (mean +/- SEM) depicting PAF estimates recorded from the C3 channel during Capsaicin Heat Pain. Estimates are shown as relative to Pain-Free 2. White dots outlined with black reflect channels belonging to a significant cluster. Red numbers are used to denote instances where multiple, significant clusters were identified. If no numbers are present within a panel, all outlined channels belong to the same cluster.

Alpha Power (AP) is decreased during two models of Prolonged Pain. A. Topoplot of the estimated effect of PHPOn on AP. PHPOn AP was found to be significantly less than Pain-Free 1 AP and significantly less than PHPOff and Pain-free 2 AP, here maximally observed over a bilateral, frontocentral cluster (1). In contrast, AP was significantly enhanced at a left, parietal cluster (2) during PHPOn relative to Pain-Free 1 and relative to PHPOff and Pain-Free 2. B. Topoplot of the estimated effect of Visit 2 on PHP AP. PHP AP was found to be significantly smaller during Visit 2 than during Visit 1 at a left (1) and right (2) posterior cluster. C. Line plot (mean +/- SEM) depicting AP estimates recorded from the C3 channel during Phasic Heat Pain. For ease of visualization, estimates are presented as relative to Pain-Free 1. D. Topoplot of the average estimated effect of CHP and CHP Rekindle on AP. AP was significantly decreased during CHP and CHP Rekindle at a left, frontocentral cluster. E. Topoplot of the estimated effect of Visit 2 on PHP AP. AP was significantly decreased during Visit 2 at a cluster extending over posterior and temporal channels on both sides of the head. F. Line plot (mean +/- SEM) depicting AP estimates recorded from the C3 channel during Capsaicin Heat Pain. Estimates are shown as relative to Pain-Free 2. For all topoplots, black dots reflect sensor-level effects surpassing the initial cluster formation threshold but not belonging to a significant cluster (see Statistics section for specific details on cluster formation for PHP and CHP analyses). White dots outlined with black reflect channels belonging to a significant cluster. Red numbers are used to denote instances where multiple, significant clusters were identified. If no numbers are present within a panel, all outlined channels belong to the same cluster.

Peak Alpha Frequency (PAF) is consistently slowed and Alpha Power (AP) is reliably decreased during both Phasic Heat Pain (PHP) and Capsaicin Heat Pain (CHP). A. Channels denoted with a black dot in the topoplot contributed to significant clusters for both PHP and CHP PAF analyses. B – C. Average, z-scored spectra from the C3 sensor during PHP-related sessions at Visits 1 and 2. Increases in 8-10 Hz AP and decreases in 10-12 Hz AP can be seen at both visits (compare blue and orange spectra). D. Channels denoted with a black dot in the topoplot contributed to significant clusters for both PHP and CHP Alpha Power analyses. E – F. Same as in B-C but for CHP-relation sessions. Decreases in 8-12 Hz power are evident throughout CHP and CHP Rekindle (compare dark blue spectra to purple and and light blue spectra).

Slowing of PAF reflects focal decreases in “fast” 10-12 Hz AP during Phasic Heat Pain (A-C), Capsaicin Heat Pain (D-F), and Capsaicin Rekindle (G-I). A. Differences between PHPOn and Pain-Free 1 spectra at Visit 1 (Black) and Visit 2 (Blue). Data is taken from the C3 channel and shaded regions reflect the 95th confidence interval. B. Same as in A., but with each row representing one of the 63 EEG channels. Increasingly warmer colors indicate greater power increases while increasingly cooler colors indicate greater power decreases. Power increases in the “fast” range are exclusive to parietal and occipital channels. C. Correlation between Pain-Free 1 PAF and power changes (PHPOn – Pain-Free 1) throughout the 8-12 Hz range for each EEG channel. Increasingly warmer colors indicate a greater positive correlation while increasingly cooler colors indicate a greater negative correlation; for ease of visualization, figures represent correlation values averaged across Visits 1 and 2. A patch of negative correlation can be seen that overlaps with the location of “fast” power decreases seen in B. D-F. Same as in A-C, except with spectral differences between CHP and Pain-Free 2. G-I. Same as in A-C, except with spectral differences between CHP Rekindle and Pain-Free 2.

For all prolonged pain tests, decreases in “fast” 10-12 Hz AP occur predominantly in individuals with PAF greater than 10 Hz. For all panels, data from the C3 channel is shown. Participants were split based on whether their Pain-Free 1 PAF from the relevant visit was above and or below 10 Hz. Bars reflect the mean +/- 1 standard deviation.

Single (A. – C.) and multiple (D. – F.) oscillator mechanisms for slowing peak alpha frequency and reducing alpha power. A. – C. In the case where a single oscillator (A) both reduces its speed and power (B), the pattern of differences will represent a sigmoid and the sum of differences will equal 0. D. – F. Two oscillators (D, red and blue denote each oscillator while the black represents their summed representation) can produce PAF and power changes without changing their frequency location (E). In this instance, spectral changes will present a focal reduction and the sum differences will not be equal to 0. Data from Figures 5 and 6 appear to more closely follow a multi-oscillator scheme.