Spectral analysis of visual potentials evoked by sine wave modulated light in migraine

Visual evoked potentials to unstructured sine wave-modulated light were measured in 30 common migraine patients and 23 controls. The fundamental and the second harmonic components of the response were analysed separately in the frequency domain by power spectrum estimation. The absolute and relative powers of the fundamental component were significantly larger in the patients at 16-22 Hz stimulation both initially, in the onset phase, and later, in the steady-state phase, whereas those of the 2nd harmonic component were smaller in the later stages of stimulation. Significant difference occurred in the dynamics of the 2nd harmonic response between patients and controls. No significant difference was observed at 10 Hz stimulation.