Long-range inhibitory mechanisms in the visual system are impaired in migraine sufferers

BACKGROUND: After viewing dynamic noise surrounding a homogeneous grey patch (artificial scotoma), observers perceive a prolonged twinkling-noise after-image within the unstimulated area. It has been suggested that noise-stimulated neurons induce a long-range inhibition in neurons within the artificial scotoma, which generates a rebound signal perceived as twinkling noise following noise termination. We used this paradigm to test whether migraineurs have enhanced excitability or weakened inhibition. METHODS: Twinkling-noise duration was measured in 13 headache-free volunteers, 13 migraineurs with aura and 13 migraineurs without aura. RESULTS: The durations of the after-image were significantly shorter for both migraine groups compared to controls. DISCUSSION: Enhanced excitation of noise-activated neurons in migraineurs would produce stronger rebound activity and longer after-image durations, while weakened inhibitory mechanisms would diminish the rebound activity and shorten the after-image durations compared to control subjects. The results suggest that cortical inhibitory mechanisms might be impaired in migraineurs with and without aura.