Altered psychophysiological responses to the view of others' pain and anger faces in fibromyalgia patients

Facial expression provides information for an accurate estimation of others' pain. Nevertheless, little is known about psychophysiological responses to pain faces in chronic pain. Event-related potentials and brain oscillations, corrugator activity, and heart rate were recorded in 20 fibromyalgia patients and 20 pain-free controls when viewing pain, anger, happy, and neutral faces. Pain and anger faces elicited greater unpleasantness and arousal than happy and neutral faces, and pain faces evoked greater corrugator response than the rest of faces in all participants. Fibromyalgia patients displayed greater cardiac deceleration to all facial expressions than pain-free controls, and enhanced N100 amplitudes to pain and anger faces in comparison with neutral faces. Pain-free controls were characterized by enhanced N100 amplitudes to happy faces as compared to patients, and by more positive event-related potential amplitudes to happy than to other faces in the time window of 200 to 300 ms. Fibromyalgia patients showed greater theta power in response to pain and anger faces, as well as more reduced alpha power than pain-free controls to all faces. These findings suggest that information processing in fibromyalgia might be characterized by enhanced defensive reactions and increased mobilization of attention resources to pain and anger faces, and by reduced allocation of attention to happy faces. Perspective: Our findings suggest that brain and cardiac activity elicited by viewing facial expressions of pain and anger in others is altered in fibromyalgia patients. This cognitive bias toward negative emotions could be used in clinical settings as a psychobiological marker during the assessment and treatment of fibromyalgia.