Pain
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This study tested the hypothesis that distraction from a painful stimulus is best achieved by concurrent presentation of a similar stimulus. Specifically, it was hypothesized that pain perception would be interfered with, and thus reduced, when a stimulus similar to the sensory features of a painful stimulus was delivered concurrently. Subjects matched aversiveness thresholds for electrocutaneous or auditory stimulation so that both forms of stimulation could be judged to be subjectively of similar affective value. ⋯ Magnitude estimation ratings of the aversiveness of counterstimulation were provided concurrently with cold pressor pain ratings, every 30 sec. The results indicated that, as predicted, subjects exposed to concurrent electrical stimulation produced lower pain ratings than subjects exposed to auditory stimulation and controls. In addition, a mutual interference effect between the cold pressor and the tactile counterstimulation was found: subjects also rated electrical stimulation as a less aversive than auditory stimulation over the duration of the cold pressor test.
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The Descriptor Differential Scale (DDS) applies psychophysical principles to clinical pain assessment. It contains 12 descriptor items for each pain dimension assessed. For each item, subjects indicate if their pain either is equal in magnitude to that implied by the anchoring descriptor, or how much greater or lesser on a 10-point graphic scale. ⋯ Ninety-one patients completed the sensory intensity and unpleasantness forms of the DDS at both 1 and 2 h after surgical extraction of a lower third molar. Results show that the DDS satisfies standard psychometric criteria for reliability, objectivity and item homogeneity. The coefficients found satisfy standard psychometric criteria and improve after elimination of inconsistent profiles.
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Inoculation of the right hind paw with Mycobacterium butyricum rapidly led to swelling and inflammation. The afflicted limb showed an enhanced sensitivity to noxious pressure (hyperalgesia) and a reduced sensitivity to noxious heat 24 h following treatment. Both naloxone and MR 2266 (which has greater activity at kappa-opioid receptors) further increased the sensitivity to pressure (that is, potentiated the hyperalgesia) but did not affect the response to heat. ⋯ The effect is specific to DYN as compared to ME and LE. The density of mu-, delta-, or kappa-receptors in the lumbar spinal cord is unmodified. (2) The altered response to opioid agonists and antagonists shown by rats with an inflamed limb may be selective to the injured tissue. (3) Alterations in opioid systems associated with unilateral hind limb inflammation may not be exclusively chronic in nature: they appear very rapidly (within 24 h) of the induction of pain. With time, the contralateral limb becomes affected and, eventually, the effects resemble those seen with generalized polyarthritis.
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Self-hypnosis was taught to 5 highly hypnotisable patients referred to Auckland Hospital Pain Clinic. Evaluation included the Illness Self-Concept Repertory Grid (ISCRG) and follow-up was at 1 and 6 months post treatment. Consensus grids indicated the subjects initially identified with physical illness but this association decreased over the course of the study. ⋯ An association between pain reduction and self-concepts is thus noted. This study does not identify whether self-concepts merely reflect therapeutic change or whether strong self-identification with physical illness indicates a poor prognosis for pain relief. This is a question which deserves further study.
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Randomized Controlled Trial Clinical Trial
Biofeedback of somatosensory event-related potentials: can individual pain sensations be modified by biofeedback-induced self-control of event-related potentials?
This study investigates the effects of biofeedback based upon event-related brain potentials evoked by nociceptive electrical stimuli. In a visual and monetary feedback paradigm, 10 subjects received positive feedback within one training session when systematically showing two different behavior patterns: one pattern correlated with a decrease (down-training) and one with an increase (up-training) of the peak-to-peak size of the N150-P260 complex, respectively. ⋯ Furthermore, the individual pain report measured with a visual analogue scale was altered in accordance with the biofeedback-induced behavioral modifications. A decrease in subjective pain report was achieved after down-training while an increase was observed after the up-training.