Pain
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The important role of operant learning in the development and maintenance of chronic pain is widely recognized. A specific type of reinforcement based on the reduction of painful stimulation when a person's perception changes in the desired direction has been termed intrinsic reinforcement of pain. In the present study, the role of intrinsic operant learning in chronic pain was tested in fibromyalgia (FM) patients with and without comorbid irritable bowel syndrome (IBS) compared with healthy persons. ⋯ Whereas healthy persons learned perceptual changes according the experimental protocol, both patient groups failed to show normal operant perceptual learning: FM patients without IBS demonstrated sensitization learning comparable to that in healthy persons, but unexpectedly these patients learned even more pronounced sensitization in the habituation learning condition, contradicting the experimental protocol; FM patients with IBS demonstrated neither learning of enhanced sensitization nor enhanced habituation; no signs of differential operant learning were observable. Thus, operant perceptual learning was impaired in FM patients; whether learning of both enhanced perceptual sensitization and habituation was impaired depended on the presence of comorbid IBS and could not be explained by other clinical characteristics of the patients such as pain threshold, duration of pain, depressive symptoms, or anxiety. While healthy participants learned sensitization and habituation according to an operant task, FM patients without IBS showed enhanced sensitization and FM with IBS no learning.
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The ability to determine precisely the location of sensory stimuli is fundamental to how we interact with the world; indeed, to our survival. Crossing the hands over the body midline impairs this ability to localize tactile stimuli. We hypothesized that crossing the arms would modulate the intensity of pain evoked by noxious stimulation of the hand. ⋯ Besides studies showing relief of phantom limb pain using mirrors, this is the first evidence that impeding the processes by which the brain localises a noxious stimulus can reduce pain, and that this effect reflects modulation of multimodal neural activities. By showing that the neural mechanisms by which pain emerges from nociception represent a possible target for analgesia, we raise the possibility of novel approaches to the treatment of painful clinical conditions. Crossing the arms over the midline impairs multimodal processing of somatosensory stimuli and induces significant analgesia to noxious hand stimulation.
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No validated screening tasks exist to distinguish children who can accurately use self-report pain measures from those who cannot. Children aged 3-7 years (n=108), each with a parent, provided data before and after day surgery. Parents rated how well they thought their child could understand the Faces Pain Scale-Revised (FPS-R), and children completed 4 screening tasks in counterbalanced order, such as rating pain in vignettes and selecting a middle-sized cup. ⋯ We failed to identify a screening tool that was better than chronological age in identifying which children could accurately self-report pain using the FPS-R. Future research should explore other screening tasks, training methods, and simplified approaches to pain assessment for young children. The ability to use self-report pain scales usually develops from age 3 to 7 years, but no valid screening method exists to identify this achievement.