Background & Aims
Pain avoidance is a key element in the vicious circle of the Fear Avoidance Model (FAM) and maintains chronic pain1. Pain avoidance is a learned instrumental response towards a discrete pain stimulus: a specific action delays or even fully eliminates the pain stimulus. New information about pain can also passively be learned based on Pavlovian associations. Interestingly, both learning types have been shown to interact2,3. In so-called Pavlovian-to-Instrumental Transfer (PIT) paradigms, reward-associated cues enhanced behaviors that previously produced rewards without the action and cue being coupled before. Testing whether this type of modulation holds in an aversive pain context would help understanding what drives pain avoidance. Such knowledge is critical in eventually breaking the FAM loop and improving the quality of life of chronic pain patients. We expect that Pavlovian learned environmental cues that predict pain will invigorate instrumentally learned pain avoidance behavior.
Methods
This PIT-PAIN study (n=62) comprised three phases. In the instrumental learning phase, participants learned to avoid electrocutaneous pain stimuli by pressing a hand dynamometer (grip) above an individually calibrated threshold. They used two grips to avoid pain on either a hand or a foot respectively. If the grip threshold was not met, pain was delivered to the respective area. In the Pavlovian learning phase pain could not be avoided. Three visual cues were conditioned: one color predicted pain on the hand, another predicted pain on the foot and a third predicted no pain. After a brief instrumental reminder phase, the final transfer phase combined both previous learning phases. The grips could be used again, now in the presence of the Pavlovian cues. Grip strength during the transfer phase was used as measure of the vigor with which pain was avoided. A linear mixed effects model was used to compare the avoidance vigor (grip strength) in the presence of cues predicting pain or safety.
Results
In the instrumental phase, participants successfully learned to avoid the pain stimuli. The average number of received painful stimulations per trial decreased over the course of three instrumental learning blocks, suggesting successful learning of i) which grip to use for which location and ii) pressing this grip hard enough to avoid the pain stimulus. Also, in the Pavlovian phase, participants successfully learned which color predicted pain on either of the two body parts and which color predicted safety. Pain expectancy ratings were higher for cues predicting pain on the hand and the foot, while pain expectancy ratings were lower for the cue predicting no pain. Thus, with our experimental paradigm, the conditions were successfully established to test the modulation between these two types of learning in the context of pain. Of main interest, at transfer, grip strength was significantly larger during trials in which Pavlovian cues predicted pain compared to trials in which Pavlovian cues predicted safety. More specifically, grip strength was the strongest when Pavlovian information about pain also corresponded to the pain location site (pain vs safe st.beta=0.76) compared to Pavlovian information about pain and the pain location being incongruent (pain vs safe st.beta=0.17).
Conclusions
This study successfully demonstrated that Pavlovian-to-Instrumental Transfer holds under aversive pain conditions. Pain avoidance behavior is invigorated by cues predictive of pain, even though cues and pain avoidance behavior were never coupled before. In addition, using dynamometers measuring grip strength as an index for avoidance behavior proved to be an efficient tool to implicitly measure the motivation of individuals to avoid pain. They nicely mirror realistic scenarios in which avoiding pain also requires some effort. This study paves to way for future studies, that could focus for example on the role of the threat value of pain as another potentially modulating factor of the demonstrated PIT-PAIN effect. It is expected that that high threat value of pain modulates the interaction between instrumental and Pavlovian learning, enhances the PIT-PAIN effect, and invigorate avoidance behavior at transfer.
References
1.Vlaeyen, J. W. S., Crombez, G., & Linton, S. J. (2016). The fear-avoidance model of pain. Pain, 157(8), 1588-1589. https://doi.org/10.1097/j.pain.0000000000000574
2.Cartoni, E., Balleine, B., & Baldassarre, G. (2016). Appetitive Pavlovian-instrumental Transfer: A review. Neurosci Biobehav Rev, 71, 829-848. https://doi.org/10.1016/j.neubiorev.2016.09.020
3.Krypotos, A. M., Sjouwerman, R., Teppers, M., & Vlaeyen, J. W. (2024). Pavlovian-to-instrumental transfer in individuals with chronic pain. Behaviour Research and Therapy, 104491.
Presenting Author
Rachel Sjouwerman
Poster Authors
Rachel Sjouwerman
PhD
Department of Experimental Health Psychology, Maastricht University, The Netherlands
Lead Author
Angelos Krypotos
Department of Clinical Psychology, Utrecht University, The Netherlands
Lead Author
Linda Vancleef
Department of Experimental Health Psychology, Maastricht University, The Netherlands
Lead Author
Johan Vlaeyen
Department of Experimental Health Psychology, Maastricht University, The Netherlands
Lead Author
Topics
- Mechanisms: Psychosocial and Biopsychosocial