Background & Aims

In everyday life, there are many situations in which a painful event must be overcome in order to receive a positive outcome. While prior studies have shown an influence of pain on decision-making [1,2], as well as effects of reward on pain [3], the role of motivation to obtain reward on pain perception has so far been insufficiently investigated. In this study, we employ a novel motivation-decision-task with the aim to systematically examine mechanisms behind how motivation, and the decision to engage in a painful action, modulate the experience of pain [4]. Here, we present behavioral data, which will be applied in an fMRI setting in the future.

Methods

A total of 22 individuals (12 female) participated in this study. At the beginning of each trial, subjects were presented a monetary offer (low, medium, or high), followed by a noxious heat stimulus of moderate or high intensity. After rating the stimulus intensity, subjects decided to accept or decline the offer. Following this decision, subjects received a second painful stimulus. During the first three seconds of the ongoing stimulus, subjects had to successfully perform a grip force task in half of the trials in order to obtain the reward. The demand of the task was to exert at least 30% of their maximal grip force for at least half of the task duration. If the offer was accepted, a stimulus of the same intensity was applied. Declining the offer led to a reduction of intensity of the second stimulus (high to moderate, moderate to low), but no reward. After cessation of the second stimulus, intensity was rated and the outcome was presented.

Results

Results showed that participants perceived less pain when they succeedingly accepted an offer than when they declined an offer of the same amount. Furthermore, a moderately painful stimulus applied after the decision was rated as less painful after accepting than after declining an offer. For the moderate pain intensities, the extent of pain reduction induced by deciding to engage in action was dependent on the amount offered, as only medium or high, but not low offers, led to significantly reduced ratings for the stimulus applied after the decision compared to ratings of the stimulus before the decision.

Conclusions

Our data provide evidence for the existence of an effect of motivation on pain processing. More specifically, our results indicate that the combination of two components evoke mechanisms of motivated hypoalgesia: i) the decision to engage in a painful action and ii) moderate to high reward expectation. Our next aim is to corroborate and extend these findings in a double-blind pharmacological intervention fMRI study using the mu-opioid receptor antagonist naloxone. Therein, we will examine the involvement of central regions of the descending pain modulatory system and the putative mediating role of the endogenous opioid system in the observed effects.

References

[1] Talmi, D., Dayan, P., Kiebel, S. J., Frith, C. D., & Dolan, R. J. (2009). How humans integrate the prospects of pain and reward during choice. Journal of Neuroscience, 29(46), 14617-14626.
[2] Slimani, H., Rainville, P., & Roy, M. (2022). The aversive value of pain in human decision?making. European Journal of Pain, 26(3), 668-679.
[3] Becker, S., Gandhi, W., & Schweinhardt, P. (2012). Cerebral interactions of pain and reward and their relevance for chronic pain. Neuroscience letters, 520(2), 182-187.
[4]Fields, H. L. (2006). A motivation-decision model of pain: the role of opioids. In Proceedings of the 11th world congress on pain (pp. 449-459). Seattle: IASP press.

Presenting Author

Leonard Asan

Poster Authors

Leonard Asan

Msc

University Medical Center Hamburg-Eppendorf

Lead Author

E-mail

Topics

  • Models: Acute Pain