We investigated whether the central pain symptoms in fibromyalgia syndrome (FM) are related to defective top-down sensorimotor regulation. The pain matrix was activated in a top-down manner by presenting pictures of painful situations while recording brain activity using magnetoencephalography (MEG). We investigated alpha desynchronisation in FM patients and healthy controls in response to pictures depicting pain.
19 FM patients and 14 age-matched healthy controls (age 20-60) were recruited. Participants were shown photographs of right hands and feet in situations depicting pain or of control situations with no depiction of pain. MEG was recorded in a whole-head 248-sensor system as subjects laid supine.
In healthy controls exposure to pictures depicting painful situations elicited a decrease in alpha activity (10Hz) at 100-500ms post-stimulus, which was significantly more pronounced than the one elicited by non-painful content mostly on sensors above the right sensorimotor cortex. However, FM patients did not show significant differences in alpha activity between responses to pain and no-pain pictures.
Consistent with previous findings, healthy participants displayed stronger alpha desynchronisation for pain pictures, indicating automatic disinhibition of the sensorimotor cortices in response to the observation of pain in others. We found evidence for a deficient modulation of sensorimotor cortex in FM patients. The lack of differential response suggests that they perceived relatively neutral pictures as potentially painful, at least in this setting. Our findings suggest that defective top-down regulation may play a role in the pathogenesis of FM.