Fig. 4

Global spectrograms of MEG data recorded from a representative chronic migraine subject, an acute migraine subject and a control during left finger movements. The spectrograms in 5–100 Hz show delayed spectral components in acute and chronic migraines (light green arrows indicate component 1, dark green arrows indicate component 2) as compared with controls. Spectral components around 70–80 Hz (white arrows) appear to be strong in chronic migraine, to be weak in acute migraine, and are not identifiable in the control. The spectrograms in 100–1000 Hz and 1000–2880 Hz reveal later components (cyan arrows) in chronic and acute migraine, but not in the controls. The vertical axis contains the frequency range (i.e., the minimum frequency at the bottom; maximum on the top). The horizontal axis contains the time window (from 10 ms to 270 ms). Below the spectrograms are bar graphs showing the spectral power of neuromagnetic activation elicited by right finger movements in chronic migraine subjects, acute migraine subjects and healthy controls. The bars show the mean and standard error of the spectral power of each group of subjects. “**” indicates p < 0.001; “*” indicates p < 0.01