Abnormal functional connectivity under somatosensory stimulation in migraine: a multi-frequency magnetoencephalography study

BACKGROUND: Although altered neural networks have been demonstrated in recent MEG (magnetoencephalography) research in migraine patients during resting state, it is unknown whether this alteration can be detected in task-related networks. The present study aimed to investigate the abnormalities of the frequency-specific somatosensory-related network in migraine patients by using MEG. METHODS: Twenty-two migraineurs in the interictal phase and twenty-two sex- and age-matched healthy volunteers were studied using a whole-head magnetoencephalography (MEG) system. Electrical stimuli were delivered alternately to the median nerve on the right wrists of all subjects. MEG data were analyzed in a frequency range of 1–1000 Hz in multiple bands. RESULTS: The brain network patterns revealed that the patients with migraine exhibited remarkably increased functional connectivity in the high-frequency (250–1000 Hz) band between the sensory cortex and the frontal lobe. The results of quantitative analysis of graph theory showed that the patients had (1) an increased degree of connectivity in the theta (4–8 Hz), beta (13–30 Hz) and gamma (30–80 Hz) bands; (2) an increased connectivity strength in the beta (13–30 Hz) and gamma (30–80 Hz) bands; (3) an increased path length in the beta (13–30 Hz), gamma (30–80 Hz) and ripple (80–250 Hz) bands; and (4) an increased clustering coefficient in the theta (4–8 Hz), beta (13–30 Hz) and gamma (30–80 Hz) bands. CONCLUSIONS: The results indicate that migraine is associated with aberrant connections from the somatosensory cortex to the frontal lobe. The frequency-specific increases in connectivity in terms of strength, path length and clustering coefficients support the notion that migraineurs have elevated cortical networks. This alteration in functional connectivity may be involved in somatosensory processing in migraine patients and may contribute to understanding migraine pathophysiology and to providing convincing evidence for a spatially targeted migraine therapy.