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Papers of the Week

Papers: 16 Jan 2021 - 22 Jan 2021

Human Studies

2021 Jan 16

J Pain

A better touch: C-tactile fibres related activity is associated to pain reduction during temporal summation of second pain.


C tactile (CT) fibres, responsible for the so-called "affective" touch (AT), have drawn a fair amount of attention within the scientific community for their marked social dimension. However, while the pain-relieving potential of discriminative touch (DT) has been documented, proofs of the analgesic properties of AT are still scarce. Additionally, no study has so far tested its possible pain-relieving effect on a clinically-relevant model. Temporal summation of second pain (TSSP), otherwise referred to as 'wind-up', relies on repetitive stimulation of C-nociceptors and it is thought to reflect central sensitization, a process linked to many chronic pain conditions. In the present experimental, within participants, design we induced TSSP trough trains of ascending and descending repetitive heat stimulation. Forty-two healthy participants' pain was measured during two different tactile stimulations (stroking velocities AT: 10 cm/s; DT: 0.3 cm/s) or without concomitant tactile input. Since measures of pleasantness of the tactile stimulation have been found to strongly correlate with C-tactile fibres' firing rate, these, together with participants' body awareness, were also taken into account. Our results show that AT brought about a decrease of our participants' pain as opposed to both DT and no touch, while DT did not produce any significant pain reduction. Thus, only AT successfully modulated wind-up. As expected, AT was perceived more pleasant than DT, while a clear relationship between body awareness and pain was found only during DT. Targeting CT fibres could pave the way to new treatments for chronic pain conditions whose aetiology depend on abnormal C-nociceptors' physiology.