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Altered Dynamic of EEG Oscillations in Fibromyalgia Patients at Rest.

OBJECTIVE
Previous fMRI findings have shown that chronic pain patients display an altered activation and functional connectivity of the pain network. The aim of the present study was to analyze EEG dynamics in fibromyalgia patients (n = 20) and pain-free controls (n = 18) at rest.


METHODS
Spectral power density, source current density, and intra- and inter-hemispheric coherence were analyzed from 64 EEG channels during 5-minutes eyes-closed rest.


RESULTS
Results indicated that fibromyalgia patients displayed reduced power density of the delta EEG band (2-4 Hz) over right insula, right superior and middle temporal gyri as compared with pain-free controls. Fibromyalgia patients also exhibited greater power density than pain-free controls in two segments of the beta band (16-23 Hz and 23-30 Hz) over right middle frontal lobe and midcingulate gyrus. Pain duration in fibromyalgia patients was negatively correlated with delta power from right insula. Greater centro-parietal intra-hemispheric coherence was observed at the left hemisphere on theta (4-8 Hz), and beta-3 (23-30 Hz) frequency bands in fibromyalgia patients than in pain-free controls. Individual differences in depression, anxiety or negative affect did not account for these findings.


CONCLUSIONS
Fibromyalgia leads to an altered dynamic of the brain network involved in the processing of pain even at rest. Furthermore ,: our results provide further support for the feasibility of resting-state EEG analyses as a clinical biomarker for the characterization of chronic pain states.