Pain
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Comparative Study
Inward currents in primary nociceptive neurons of the rat and pain sensations in humans elicited by infrared diode laser pulses.
Radiant heat is often used to study nociception in vivo. We now used infrared radiation generated by a diode laser stimulator (wavelength 980 nm) to investigate transduction mechanisms for noxious heat stimuli in acutely dissociated dorsal root ganglion (DRG) neurons of rats in vitro. The laser stimulator offered the unique opportunity to test whether the same stimuli also elicit pain sensations in humans. ⋯ No significant differences were seen between the pain thresholds in hairy and in glabrous skin, probably due to the deep penetration of this laser radiation. The mean pain threshold for stimuli > or =200 ms in humans was 2.5 +/- 0.2 J mm(-2) (n = 11), and did not differ from the thresholds for the induction of I(heat) in vitro. Our results indicate that I(heat) in primary sensory neurons can be activated by infrared laser pulses that are painful in humans.
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Facial expression of pain has rarely been researched in the context of facial expression of negative emotions with which it may occur. The main aim of the study was to investigate how pain expression resembled or differed from that of other negative emotions (fear, anger, sadness, surprise, disgust and embarrassment), using multidimensional scaling, a dimensional approach to understanding relationships among emotions. As possible misidentification of facial expressions by participants could distort those results, a judgement study as a categorical approach was conducted to examine the accuracy of identification of pain and negative emotion facial expressions. ⋯ Confidence in ratings approximated accuracy of identification. Multidimensional scaling revealed two dimensions: the first distinguished embarrassment from all other emotion expressions; the second separated pain, sadness and anger from fear, surprise and disgust. Possible explanations for these findings were sought in patterns of facial action units, and in the messages conveyed by the expressions according to Fridlund's Behavioural Ecology View.
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The aim of the present study was to examine the association between pain catastrophizing and general health status in a Dutch adult community sample, including various subgroups of people with musculoskeletal pain in the analyses. For exploratory reasons this study partly replicated previous studies of the factor structure, reliability, and validity of the Pain Catastrophizing Scale (PCS). Results demonstrated that across different pain subgroups, catastrophizing uniquely contributed variance to the prediction of the various aspects of general health status beyond the variance explained by pain intensity, age, gender, and chronicity. ⋯ This implies that a one-factor model might be justifiable as well, at least in the general community. Across various pain subgroups the reliability of the PCS total and subscales was adequate. Additional evidence for the concurrent validity of the PCS was found as well.
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To obtain parents' identification and description of the behaviors, health care procedures and daily living situations associated with pain in children with cerebral palsy (CP), surveys were sent to parents of children with CP recruited via a clinic case list and a parents' newsletter. Forty-three parents completed the survey. Results indicated that children's ability to communicate pain verbally did not influence whether or not their parent reported observing pain. ⋯ Range of motion manipulation was the therapy most frequently identified as painful by parents (58%), and the one with the highest mean intensity. Parents are able to observe pain in their children with CP regardless of the child's verbal fluency. Knowledge of behaviors and painful situations identified by parents can facilitate management of pain in children with CP.
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Laser evoked potentials (LEPs) are brain responses to activation of skin nociceptors by laser heat stimuli. LEPs consist of three components: N1, N2, and P2. Previous reports have suggested that in contrast to earlier activities (N1), LEPs responses after 230-250 ms (N2-P2) are modulated by attention to painful laser stimuli. ⋯ Conversely, processes underlying P2 (400 ms) were not affected by spatial attention, but by the probability of the stimulus. This probability effect was not due to P3b-related processes that were observed at a later latency (600 ms). Indeed, P600 could be seen as a P3b evoked by conscious detection of rare targets.