Abnormal affective modulation of somatosensory brain processing among patients with fibromyalgia

Objective: It is well established that subjective pain perception can be modulated by negative mood states and that patients with chronic pain are characterized by high levels of depression and anxiety. Nevertheless, very little is known about the effects of negative mood induction on brain processing of somatosensory information in fibromyalgia. The objective of the present study was to examine the influence of two emotional states (pleasant and unpleasant) on brain activity of patients with fibromyalgia (FM; n = 27) and with musculoskeletal (MSK) pain resulting from identifiable somatic lesions (n = 16). Methods: For this purpose, somatosensory-evoked potentials (SEPs) elicited by nonpainful pneumatic stimuli, delivered to the right and left hand following an oddball paradigm, were recorded when patients were viewing affective slides. Results: As compared with patients with MSK pain, patients with FM displayed overall larger P50 amplitude to tactile stimuli. In addition, significantly larger P50 and smaller N80 amplitudes were found within patients with FM when they were viewing the unpleasant rather than the pleasant slides. Conclusion: Our data suggest an abnormal processing of nonpainful somatosensory information in FM, especially when somatic signals are arising from the body within an aversive stimulus context. These findings provide further support for the use of biopsychosocial models for understanding FM and other chronic pain states. Key words: emotions, cognition, somatosensory processing, fibromyalgia, chronic pain, brain.