Journal: European Journal of Pain

Abbreviation

Eur J Pain

Publisher

Wiley

Journal Volumes

ISSN

1532-2149
1090-3801

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2025 - 20263
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Publications 1 - 3 of 3
  • What a Sham(e): Sham-Controlled Conditioned Pain Modulation Effects on Pressure but Not Heat Pain Thresholds in Healthy Volunteers
    Item type: Journal Article
    Hau, Madeleine; Sirucek, Laura; De Schoenmacker, Iara; et al. (2025)
    European Journal of Pain
    Background: Conditioned pain modulation (CPM) is a well-established experimental paradigm to study descending pain modulation in humans, measuring the pain modulatory effect of a painful conditioning stimulus (CS) on a painful test stimulus (TS). Control conditions using a non-painful CS accounting for modulatory effects not attributable to the painfulness of the CS are seldom included. Thus, this study aimed to differentiate CPM effects from perceived changes of the TS unrelated to the painfulness of the CS by comparing effects of a painful and a control CS on four different TS. Methods: Forty-nine healthy participants underwent a combined parallel and sequential CPM paradigm with a cold water bath (median NRS 8/10) as painful and an ambient-temperature sham water bath (median NRS 0/10) as non-painful control CS. TS were pressure and heat pain thresholds (PPT, HPT) (parallel and sequential) and temporal summation of pain (TSP, sequential) (pressure and heat). Larger TS changes with the painful compared to the control CS were interpreted as sham-controlled CPM effects. Results: A parallel sham-controlled CPM effect was only detected for PPT (significantly larger PPT increases during the painful compared to the control condition (p = 0.009)). HPT increased for both conditions without a significant difference between conditions (p = 0.152). TSP was successfully induced but not modulated by either CS (p > 0.05). Conclusion: This study demonstrates sham-controlled CPM effects on PPT, but not on HPT, most likely due to heat adaptation or habituation. This challenges the interpretation of prior studies using CPM paradigms with HPT as TS without a control condition. Significance: This study highlights the importance of including control conditions in CPM paradigms using HPT as TS. HPT increased similarly during a painful and a control condition, most likely due to adaptation and habituation. Although these are known effects, CPM studies rarely control for them. Pressure pain thresholds increased more during the painful than during the control condition, making it a more suitable TS, especially when a control condition is absent.
  • Differential Operant Conditioning of Emotional-Motivational and Sensory-Discriminative Pain Responses
    Item type: Journal Article
    Flury , Melissa L.; Löffler , Martin; Gour , Shaili; et al. (2026)
    European Journal of Pain
    Background The experience of pain consists of different components, including sensory-discriminative and emotional-motivational components. While these components are often well aligned, they can also dissociate. Operant conditioning may selectively modulate one component without affecting the other. However, evidence directly comparing operant conditioning effects on both emotional-motivational and sensory-discriminative components of pain is lacking. The aim of the present study was to test whether operant conditioning would differentially affect behavioral surrogate measures of emotional-motivational and sensory-discriminative pain responses. Methods 62 healthy participants performed in two testing sessions a pain avoidance task to assess emotional-motivational pain responses and a temperature discrimination task to assess sensory-discriminative pain responses (counterbalanced order). In the second half of each task, successful pain avoidance or accurate temperature discrimination was followed by monetary reinforcement. Results Contingent reinforcement selectively enhanced pain avoidance, evidenced by faster reaction times and increased success rates, while temperature discrimination performance remained unchanged, likely due to a ceiling effect in task difficulty. Operantly conditioned changes in pain behaviour did not generalize to self-reported pain intensity and unpleasantness ratings. Conclusions These findings indicate a modulation of emotional–motivational pain processing by operant conditioning, while effects on sensory–discriminative processing remain absent. These results support the idea that enhanced pain perception in chronic pain can be induced by operant learning, potentially through the specific learning of increased emotional–motivational pain responses. Significance Statement This study demonstrates that operant conditioning can enhance avoidance responses, serving as an indicator of emotional–motivational pain responses. In contrast, sensory–discriminative aspects of pain were not modulated by operant conditioning. These results confirm the important role of operant conditioning specifically in emotional–motivational pain processing. This insight may help explain how learning contributes to increased emotional–motivational pain processing in chronic pain.
  • Hypercapnia Reduces Perceived Heat Pain in Healthy Subjects
    Item type: Journal Article
    Guekos, Alexandros; Hau, M.; Grob, Sabina; et al. (2025)
    European Journal of Pain
    BackgroundDanger signals modulate pain perception. Both amplification and attenuation of perceived pain are observed in healthy subjects exposed to danger signals, such as transient threats of an imminent electrical shock. However, exposure to danger signals in real life typically is not transient but constant over minutes to hours. Here, this was experimentally achieved by administering hypercapnic air (7.5% CO2). The primary objective was to investigate whether perceived heat pain would be differentially modulated during this intervention compared to regular air administration. The secondary objective assessed the potential differences of such a modulation with respect to heat intensity level.MethodsThirty-eight participants (19 women) received two air mixtures (hypercapnic and regular air) for 13 min each, during which 18 (6 x 3) noxious heat stimuli of three different intensities were applied to the calf and rated on two scales (intensity and pleasantness/unpleasantness). Psychological and physiological states were compared between conditions using the body sensations questionnaire, self-assessment manikins, heart rate, and galvanic skin response. Statistical analyses were performed using Bayesian estimation testing.ResultsBetween-condition differences were statistically meaningful for all heat intensity levels, always showing reduced pain perception during hypercapnia compared to normocapnia. The magnitude of the observed hypoalgesia did not depend on heat intensity levels.ConclusionsThe presence of a continuous physiological danger signal results in hypoalgesia. Future studies need to determine whether the present results only hold for hypercapnia in healthy subjects or are generalisable to interactions between pain perception and continuous physiological danger signals in clinical pain populations.Significance StatementIt was shown that hypercapnia leads to reduced perception of noxious heat stimuli. If confirmed by neural data in future studies this could help to better understand the interaction of pain perception and continuous physiological danger signals in clinical pain conditions, potentially allowing for improved treatment of affected individuals.
Publications 1 - 3 of 3