van den Broeke, E. N. | Search bioRxiv

bioRxiv2025

Interindividual variations in peak alpha frequency do not predict the magnitude or extent of secondary hyperalgesia induced by high-frequency stimulation

BackgroundPrevious studies have shown an association between interindividual variations in the frequency of alpha-band EEG oscillations such as estimates of peak alpha frequency (PAF) and pain sensitivity. Whether differences in PAF also influence the susceptibility to develop central sensitization (CS) is unknown. ObjectiveThis study aimed to determine if the PAF of vision- and sensorimotor-related alpha-band activity is associated with the magnitude and extent of secondary mechanical hyperalgesia induced by high-frequency stimulation (HFS) of the skin, a surrogate marker of CS. MethodsThe EEG was recorded in 32 healthy participants at rest during eyes open and eyes closed conditions, and during bilateral finger movements. Two methods were used to isolate vision- and sensorimotor-related alpha-band activity based on sensitivity to eye closure and movement: one based on an independent component analysis, the other on spectral subtraction. PAF was assessed using a center-of-gravity approach or the Fitting Oscillations and One-Over-F (FOOOF) method, accounting for the aperiodic EEG component. HFS was applied to the right forearm, and pinprick sensitivity was assessed at both forearms, before and 40 minutes after HFS. ResultsNeither sensorimotor-nor vision-related PAF were significantly correlated with the magnitude or extent of HFS-induced secondary hyperalgesia. Interestingly, at the non-sensitized forearm, participants with a higher vision-related PAF exhibited greater habituation to pinprick stimuli, suggesting that variations in PAF may relate to variations in sensory habituation. ConclusionInterindividual variations of PAF were not significantly associated with the susceptibility to develop HFS-induced secondary hyperalgesia. New and NoteworthyUsing several methods to estimate vision- and sensorimotor-related peak alpha frequency (PAF) in the EEG frequency spectrum, we found no significant association between interindividual variations in PAF and the susceptibility to develop secondary hyperalgesia following high-frequency stimulation (HFS) of the skin in healthy participants.

neuroscience↗

bioRxiv2018

Central sensitization increases the pupil dilation elicited by mechanical pinprick stimulation

High frequency electrical stimulation (HFS) of skin nociceptors triggers central sensitization, manifested as increased pinprick sensitivity of the skin surrounding the site at which HFS was applied. The aim of the present study was to compare the effects of HFS on pupil dilation and brain responses elicited by pinprick stimulation delivered in the area of increased pinprick sensitivity. In fourteen healthy volunteers HFS was applied to one of the two forearms. Before and twenty minutes after applying HFS, mechanical pinprick stimuli (64 mN and 96 mN) were delivered to the area surrounding the site at which HFS was applied as well as the contralateral control arm. During pinprick stimulation both the pupil size and electroencephalogram were recorded. HFS induced a clear and comparable increase in pinprick sensitivity for both the 64 and 96 mN stimulation intensity. Both pinprick stimulation intensities elicited a greater pupil dilation response when delivered to the area of increased pinprick sensitivity. However, this greater pupil dilation response was larger for the 64 mN compared to the 96 mN stimulation intensity. A similar pattern was observed for the negative wave of the pinprick-evoked brain potentials (PEPs), however, the increase was not significant for the 96 mN and showed only a trend towards significance for the 64 mN. These results show that there is a correspondence between the increase in pupil dilation and the increase in PEPs, but that pupil size is a more sensitive measure for detecting the effects of central sensitization than PEPs.

neuroscience↗