Pain
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Previous studies using a primary task procedure have demonstrated that an experimental pain stimulus interrupts ongoing task performance in healthy volunteers and patients, and that this interruption is intensified by catastrophic thinking about pain and the perceived threat value of the pain stimulus. However, no studies have investigated the interruption of attention by relevant threatening stimuli in specific patient samples. ⋯ The patients showed a more pronounced deterioration of performance compared to controls when the neck rotation and extension fixations were introduced. Within the groups, neither catastrophic thinking nor fear predicted the magnitude of the performance deterioration.
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The contribution of the amygdala to neuropathic pain processing in animals has not been clearly acknowledged. To assess the relative contribution of amygdala GABA-A receptors in mediating sensory-discriminative and affective-motivational pain components, the GABA-A receptor agonist muscimol and the antagonist bicuculline (both 10-25 ng/microl) were administered by acute bilateral injection directly into the central amygdala in rats with a chronic constriction injury (CCI). Escape/avoidance behaviour reflecting the affective-motivational dimension of pain was measured using a light/dark chamber in combination with suprathreshold nociceptive stimulation, and was defined as a shift from the 'non-aversive' dark area of the chamber to the 'aversive' light area. ⋯ Motility behaviour was unaffected by injection of either drug as determined in the open field test. Thus, amygdala GABA-A receptors appear to play an important role in sensory and especially affective pain processing in neuropathic rats. Furthermore, after nerve injury reflex nociceptive behaviours appear to be under tonic control by descending inputs, which originate from or are modulated within the amygdala.