Central nervous activity during implicit processing of emotional face expressions in fibromyalgia syndrome

Fibromyalgia syndrome (FMS) is characterized by chronic widespread pain accompanied by symptoms like fatigue, insomnia, depression, anxiety and cognitive impairments. In addition to central nervous pain sensitization, emotional dysregulation may be involved in FMS pathogenesis. This study investigated central nervous correlates of affective and attentional processing in FMS using an implicit task.

Event-related potentials (ERPs) of the EEG were recorded in 25 FMS patients and 37 healthy controls while they had to name the frame color of pictures displaying emotional expressions (angry, painful, happy, neutral). The actual picture had to be ingored. Symptoms of pain, depression and anxiety were also assessed.

Patients exhibited smaller P2 and late positive potential (LPP) amplitudes, and a greater N250 amplitude, than controls. The N250 amplitude varied according to the emotional expressions displayed in patients, but not in controls. No group differences arose for the P1 or N170 amplitudes. Patients had longer reaction times and made more errors on the task; task performance was more closely related to pain severity than to other symptoms.

The reduced P2 and LPP amplitudes indicate deficient short-term mobilization of attentional resources and sustained attention in FMS; the greater N250 amplitude may reflect greater engagement in the decoding of complex facial features, which is necessary to compensate for attentional impairments. Affective modulation of the N250 suggests that the neural mechanisms underlying complex visual processes are particularly susceptible to emotional influences in FMS. The behavioral data confirm attentional deficits in the disorder and implicate clinical pain therein.