Friday, July 26, 2019

Delayed effects of attention on pain sensitivity and Conditioned Pain Modulation

Abstract

Background

Efficacy of pain modulation is assessed as the difference in pain sensitivity during a painful conditioning, compared to before (conditioning pain modulation, CPM). Attention can be assessed with the Stroop‐task, in which participants report the number of words on a screen; either congruent or incongruent with the value of the words. Attention away from painful stimuli during CPM enhances the CPM‐effect. However, it is unknown if attention influences CPM‐effects when the two are done in sequence.

Methods

Healthy men (n=25) underwent cuff‐algometry CPM‐assessment where the pressure‐pain detection and tolerance thresholds (PTT) were recorded on one leg with and without contralateral conditioning. Two identical sessions of four test‐stimuli equal to PTT (5s, 1‐min interval, scored on a visual analogue scale, VAS) with a painful conditioning from the second to the last test‐stimulus were performed. Stroop‐sessions were followed by test‐stimuli with or without painful conditioning.

Results

The VAS scores in the first two sessions showed excellent reliability (ICC=0.92). VAS scores were lower in sessions with Stroop compared to sessions without Stroop (p=0.05) indicating an analgesic effect of Stroop. Participants were sub‐grouped into CPM‐responders and CPM‐non‐responders according to CPM‐effects in the first two sessions. CPM‐non‐responders (n=13) showed facilitation to repeated noxious stimuli in all sessions with no effect of conditioning or Stroop (p=0.02).

Conclusion

Attention and CPM both modulate pain in healthy men. Attention‐induced analgesia works in CPM‐non‐responders. Results indicate that attention and CPM are not the same and that they do not demonstrate additive effects when applied in sequence.

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