Abstract
BackgroundClassical conditioning has frequently been shown to be capable of evoking fear of pain and avoidance behavior in the context of chronic pain. However, whether pain itself can be conditioned has rarely been investigated and remains a matter of debate. Therefore, the present study investigated whether pain threshold ratings can be modified by the presence of conditioned non-nociceptive sensory stimuli in healthy participant.MethodsIn 51 healthy volunteers, pain threshold to electrocutaneous stimuli was determined prior to participation in a simultaneous conditioning paradigm. Participants underwent an acquisition phase in which one non-painful vibrotactile stimulus (CS+) was repeatedly paired with a painful electrocutaneous stimulus, whereas a second vibrotactile stimulus of the same quality and intensity (CS−) was paired with a non-painful electrocutaneous stimulus. Stimulation was provided on the lower back with close proximity between the conditioned stimulus and the unconditioned stimulus. In the test phase, electrocutaneous stimuli at the individually-set threshold intensity were simultaneously delivered together with either a CS+ or CS−. Pain intensity ratings were obtained after each trial; expectancy ratings were obtained after each block. The primary outcome was the percentage of test stimuli that were rated as painful.ResultsTest stimuli were more likely to be rated as painful when they were paired with the CS+ than when they were paired with the CS−. This effect was not influenced by contingency awareness, nor by expectancies or mood states.DiscussionThe findings support the notion that the judgement of an event being painful or non-painful can be influenced by classical conditioning and corroborate the possible role of associative learning in the development and maintenance of chronic pain.
Highlights
The development of chronic pain, that is, the persistence of pain long after tissue healing, is not well understood
It is assumed that during acute pain, nociceptive signaling serves as the unconditioned stimulus (US), and occurs alongside non-nociceptive signaling such as touch, proprioception and haptic perception, which serves as the conditioned stimulus (CS), such that the association of both stimuli is stored in memory
This study provides evidence that ratings of at-pain-threshold electrocutaneous stimuli can be modified through classical conditioning
Summary
The development of chronic pain, that is, the persistence of pain long after tissue healing, is not well understood. It is assumed that during acute pain, nociceptive signaling serves as the unconditioned stimulus (US), and occurs alongside non-nociceptive signaling such as touch, proprioception and haptic perception, which serves as the conditioned stimulus (CS), such that the association of both stimuli is stored in memory. According to this model, the CS carries information about the occurrence of the US: a stimulus repeatedly paired with pain (CS+) indicates danger and elicits the expectancy of pain, while a stimulus paired with non-painful sensations (CS-) indicates safety (Domjan, 2005). Discussion: The findings support the notion that the judgement of an event being painful or non-painful can be influenced by classical conditioning and corroborate the possible role of associative learning in the development and maintenance of chronic pain
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