Márcia da-Silva, Ana Rita Pereira, Adriana Sampaio, Joana Coutinho and Alberto J. González-Villar published the article “The effects of C-tactile stimulation on temporal summation of second pain: A study of the central and peripheral neural correlates” in the Brain Research journal.
The study shows that affective touch, mediated by specialized receptors known as C-tactile afferents (CT), may have a significant impact in the way we understand pain. These afferents are sensitive to gentle and slow touches, and although we already know that their activation may help reduce subjective pain, little has been explored about how these influence the central sensitization of pain.
The research included 37 participants that underwent a Temporal Summation of Second Pain (TSSP) protocol, a phenomenon in which the pain perception is intensified due to repeated noxious stimuli. During the study, the participants were submitted to three different conditions: TSSP alone, TSSP during vibrotactile stimulation and TSSP during CT stimulation, administered with a brush mounted on a robot arm.
Participants reported a significantly lower increase of pain during CT stimulation compared to vibrotactile stimulation, but not to TSSP alone. In addition, the response to pain was reduced when the CT stimulation was applied to the same side of the body in which the pain was felt, in comparison to other types of stimulation. Other data also show that the participants’ attention towards noxious stimuli, the electrical activity in the brain (measured by the N2-P2 complex), and heart rate were also reduced during CT stimulation.
The results suggest that activation of CT receptors may decrease the sensitization of pain, possibly because it diverts attention from noxious pain. Therefore, affective touch may be a promising tool to relieve pain.