I am a
Home I AM A Search Login

Papers of the Week

Papers: 18 Nov 2023 - 24 Nov 2023

2023 Nov 21

J Pain


Temporal summation of the thermal grill illusion is comparable to that observed following noxious heat.


Horing B, Kerkemeyer M, Büchel C


The thermal grill illusion (TGI) describes a peculiar or even painful percept caused by non-noxious, interlaced warm and cold stimuli. It involves the glutamatergic system and is affected in putatively nociplastic syndromes such as fibromyalgia. The glutamatergic system is also involved in wind-up, that is, the increased activation of spinal neurons following repeated noxious stimulation leading to a temporal summation of perceived stimulus intensity. Here we combined both stimulation methods to further investigate whether non-noxious stimuli as employed in the TGI can lead to a similar summation of perceived stimulus intensity. In an experiment using a full crossover within-subjects design, 35 healthy volunteers received repeated stimuli, either in a thermal grill configuration, or simply noxious heat. Both modalities were presented as sequences of 1 lead-in contact, followed by 11 consecutive contacts (each between 1.5 and 3s), with either fast repetition (“wind-up” condition), or two slow-repeating control conditions. Main analyses concerned the relative pre-to-post sequence changes to quantify putatively wind-up-related effects. Pain ratings and skin conductance level (SCL) increased more strongly in “wind-up” than control conditions. Interestingly, wind-up-related effects were of the same magnitude in TGI as compared to the pain control modality. Further, contact-by-contact SCL tracked how the effect emerged over time. These results indicate that although TGI does not involve noxious stimuli it is amenable to temporal summation and wind-up-like processes. Since both phenomena involve the glutamatergic system, the combination of wind-up with the TGI could yield a promising tool for the investigation of chronic pain conditions. PERSPECTIVE: Using thermal stimuli in an experimental protocol to combine a) the thermal grill illusion (painful or peculiar percept from simultaneous cold/warm stimulation) and b) wind-up (increase in stimulus intensity after repeated exposure) holds promise to investigate pain and thermoceptive mechanisms, and chronic pain conditions.