Source Data for Published Study "Are changes in nociceptive withdrawal reflex magnitude a viable central sensitization proxy? Implications of a replication attempt"

Upload version NWR_v01_20230409

Authors: Alexandros Guekos, Alince Catrine Grata, Michèle Hubli, Martin Schubert, and Petra Schweinhardt

The present data was collected from August to October 2019 as part of a replication attempt of a previously published study (Ellrich, J., and R-D. Treede. "Convergence of nociceptive and non-nociceptive inputs onto spinal reflex pathways to the tibialis anterior muscle in humans." Acta physiologica scandinavica 163.4 (1998): 391-401, https://doi.org/10.1046/j.1365-201X.1998.t01-1-00392.x). 

The results of the replication study have been published under open access (Guekos, A., et al. "Are changes in nociceptive withdrawal reflex magnitude a viable central sensitization proxy? Implications of a replication attempt" Clinical Neurophysiology 145 (2023): 139-150, https://doi.org/10.1016/j.clinph.2022.09.011).

Details of the paradigm, the experimental setup, and the analysis can be found there.

In brief, 16 healthy adults (8 men and 8 women) underwent a single experimental session during which a tonic heat stimulus was applied on one leg to the foot sole and on the other to the calf muscle. Both legs were tested consecutively in pseudorandom order. Concurrently, subjects received transcutaneous electrical stimuli to elicit the nociceptive withdrawal reflex (NWR). The muscle responses were recorded via surface electromyography (sEMG) from the biceps femoris (BF), rectus femoris (RF), and tibialis anterior (TA).

The protocol consisisted of eight blocks per leg. During the first two blocks no temperature stimulation was applied. These two blocks served to identify the NWR threshold at the BF. For threshold determination, a single ascending staircase with either single electrical stimulations or triplets (at 2Hz) were used. From the triplets, only the muscle response to the third stimulation was analysed. The higher of the two obtained currents was used as the threshold. The following six blocks used six different temperatures (one per block) of 32, 36, 39, 42, 45 and 46 centigrade. During each block eight transcutaneous electrical stimuli were applied, either to the medial plantar nerve (MP) on the foot sole or to the retromalleolar pathway of the sural nerve (SU). The stimulations increased from -4 mA w.r.t. threshold to 200% threhold. Participants verbally rated perceived pain for every stimulation during these six blocks.

Every electrical stimulation consisted of a train of five rectangular stimuli of 1 ms duration delivered at 200 Hz. Muscle responses were recorded from 120 pre- to 380 ms post-stimulation. The recorded sEMG signals were sampled at 48 kHz and downsampled to 6 kHz, rectified, band-pass filtered from 10 Hz to 500 Hz and amplified up to 125 times. Between 120 ms pre- and 380 ms post-stimulation, traces for all applied stimulations were automatically saved into separate txt files.

Please consult the README.txt file for details on the structure of the uploaded data and for information w.r.t. potential instances of incompleteness or unusability.

The study was funded by the Swiss National Science Foundation as part of a grant to PS (grant number 320030_179191/1).