EEG-based sensory testing reveals altered nociceptive processing in elite endurance athletes

Figures

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  Fig. 1. Raw EEG data and spectral changes of the pinprick-evoked potentials in the controls and elite endurance athletes at electrode Cz. Upper row: event-related potential (ERP). Original EEG data in the amplitude-time spectrum after pinprick stimulation for both the controls and the elite endurance athletes. Traces are the means across all 12 trials per participant and all 26 participants. The shaded area indicates the standard deviations of the 26 participants. Middle row: Average event-related spectral perturbation (ERSP), i.e., the spectral changes over time. The white arrow indicates the N2P2 response, while the black arrow indicates a response not visible in the ERP analysis. Lower row: inter-trial coherence (ITC) or phase locking factor (PLF), i.e., the spectral synchronization among the trials

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  Fig. 2. Elite endurance athletes show stronger pinprick-evoked potentials at electrode Cz, compared to controls. Panel 1 shows the event-related spectral perturbation of the controls, likewise, panel 2 shows that of the elite endurance athletes. Third panel: The statistical comparison includes both a common non-parametric statistical testing with a cluster-based correction for multiple comparisons, and the AUROC effect size. Pixels that are significantly different are colored red/orange or blue, according to the c-axis next to the image, which indicates the AUROC effect size of the comparison. The gray-shaded area in the statistics image indicates that the accompanying pixel in the ERSP in either one of the groups exceeds a [2 dB; − 2 dB] range; areas of interest for further analysis are highlighted in panel 1 with a white (early low-frequency response) and black arrow (late high-frequency response). The fourth panel shows the average ITC calculated for all 52 participants to help the reader to identify the area where the N2P2 component is commonly found

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  Fig. 3. Elite endurance athletes show stronger contact-heat-evoked potentials at electrode location Cz, compared to controls. Panel 1 shows the event-related spectral perturbation of the controls, likewise, panel 2 shows that of the elite endurance athletes. Third panel: The statistical comparison includes both a common non-parametric statistical testing with a cluster-based correction for multiple comparisons, and the AUROC effect size. Pixels that are significantly different are colored red/orange or blue, according to the c-axis next to the image, which indicates the AUROC effect size of the comparison. The gray-shaded area in the statistics image indicates that the accompanying pixel in the ERSP in either one of the groups exceeds a [2 dB; − 2 dB] range. The fourth panel shows the average ITC calculated for all 52 participants to help the reader to identify the area where the N2P2 component is commonly found

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  Fig. 4. The conditioning stimulus during conditioned pain modulation testing affects the N2P2 component only in the elite endurance athletes, but not in the controls. A noxious cold water bath at 8 °C was used as the conditioning stimulus (CS). The event-related spectral perturbation (ERSP) of pinprick-evoked Potentials (PEP as the test stimulus) plotted before, during and after the conditioning stimulus for the controls (A, B and C) as well as for the elite endurance athletes (D, E and F). The right panels show a statistical comparison between the conditions before vs. during and during vs. after for both groups; the bottom panel shows a group comparison between the groups for each condition. The gray-shaded area in the statistics image indicates that the accompanying pixel in the ERSP in either one of the groups, or conditions, exceeds a [2 dB; − 2 dB] range, and is considered an EEG response to the stimulus. Furthermore, our areas of interest are highlighted in panel 1 with a white and black arrow (white arrow for the early low-frequency response, black arrow for the late high-frequency response). The statistical comparison includes both a common non-parametric statistical testing…

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  Fig. 5. Study flow for each participant