Although humans differ widely in how sensitive they are to painful stimuli, the neural correlates underlying such variability remains poorly understood. A better understanding of this is important given that baseline pain sensitivity scores relate closely to the risk of developing refractory, chronic pain. To address this, we used a matched perception paradigm which allowed us to control for individual variations in subjective experience. By measuring subjective pain, nociceptive flexion reflexes, and, somatosensory evoked brain potentials (with source localization analysis), we were able to map the brain's sequential response to pain while also investigating its relationship to pain sensitivity (i.e. change in the stimulation strength necessary to experience pain) and spinal cord activity. We found that pain sensitivity in healthy adults was closely tied to pain-evoked responses in the contralateral precuneus. Importantly, the precuneus did not contribute to the actual representation of pain in the brain, suggesting that pain sensitivity and pain representation depend on separate neuronal sub-systems.

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Our results further confirm that MDD is associated with decreased serotonin levels, but that serotonin levels are not altered in FM per se, and suggest that 5-Hydroxytryptamine is related to mood symptoms in these patient groups. Our results also suggest that the taking of antidepressant is a major confound to consider when studying serotonin functioning in FM. The long-term use of antidepressants in FM may lead to serotonin depletion. Conversely, serotonin depletion may be before the taking of antidepressants in FM.

These age differences clearly warn against consolidating the QOL or QOH scores of younger and older adults, and instead suggest that age at diagnosis is essential when considering patient perspective, and when establishing tailored support programs.