Thermonociceptive interaction: interchannel pain modulation occurs before intrachannel convergence of warmth

Cataldo, A. and Ferrè, Elisa Raffaella and Haggard, P. (2019) Thermonociceptive interaction: interchannel pain modulation occurs before intrachannel convergence of warmth. Journal of Neurophysiology 121 (5), pp. 1798-1808. ISSN 0022-3077.

Abstract

Nonnoxious warmth reduces both perceived pain intensity and the amplitude of EEG markers of pain. However, the spatial properties of thermonociceptive interaction, and the level of sensory processing at which it occurs, remain unclear. We investigated whether interchannel warmth-pain interactions occur before or after intrachannel spatial summation of warmth. Warm stimuli were applied to the fingers of the right hand. Their number and location were manipulated in different conditions. A concomitant noxious test pulse was delivered to the middle finger using a CO2 laser. We replicated the classical suppressive effect of warmth on both perceived pain intensity and EEG markers. Importantly, inhibition of pain was not affected by the location and the number of thermal stimuli, even though they increased the perceived intensity of warmth. Our results therefore suggest that the inhibitory effect of warmth on pain is not somatotopically organized. The results also rule out the possibility that warmth affects nociceptive processing after intrachannel warmth summation.

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