Abstract
Pain is evolutionarily hardwired to signal potential danger and threat. It has been proposed that altered pain-related associative learning processes, i.e., emotional or fear conditioning, might contribute to the development and maintenance of chronic pain. Pain in or near the face plays a special role in pain perception and processing, especially with regard to increased pain-related fear and unpleasantness. However, differences in pain-related learning mechanisms between the face and other body parts have not yet been investigated. Here, we examined body-site specific differences in associative emotional conditioning using electrical stimuli applied to the face and the hand. Acquisition, extinction, and reinstatement of cue-pain associations were assessed in a 2-day emotional conditioning paradigm using a within-subject design. Data of 34 healthy subjects revealed higher fear of face pain as compared to hand pain. During acquisition, face pain (as compared to hand pain) led to a steeper increase in pain-related negative emotions in response to conditioned stimuli (CS) as assessed using valence ratings. While no significant differences between both conditions were observed during the extinction phase, a reinstatement effect for face but not for hand pain was revealed on the descriptive level and contingency awareness was higher for face pain compared to hand pain. Our results indicate a stronger propensity to acquire cue-pain-associations for face compared to hand pain, which might also be reinstated more easily. These differences in learning and resultant pain-related emotions might play an important role in the chronification and high prevalence of chronic facial pain and stress the evolutionary significance of pain in the head and face.
Highlights
IntroductionLearning about signals or situations that predict pain is a highly adaptive response as it allows to prepare for upcoming pain and to effectively cope with it, for instance by initiating protective behavior [1,2,3]
Pain is evolutionarily hardwired to signal potential danger and threat
Regarding a spontaneous recovery of previously extinguished emotional responses, we observed a significant increase in negative valence for the conditioned stimuli (CS)+Face (β: 4.26 ± 1.84, t(390.19) = 2.31, p = 0.02, d = 0.23) and an increase in negative valence at trend level for the CS+Hand (β: 3.22 ± 1.84, t(390.24) = 1.75, p = 0.08, d = 0.24) indicating spontaneous recovery with comparable, small effect sizes for both CS+
Summary
Learning about signals or situations that predict pain is a highly adaptive response as it allows to prepare for upcoming pain and to effectively cope with it, for instance by initiating protective behavior [1,2,3]. Pain signals might initiate maladaptive responses such as increased negative emotions, e.g. fear of pain [4] as described in the fear-avoidance model of chronic pain [2, 5]. These anticipatory negative emotions might lead to an aggravation of pain experiences [6, 7].
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