The experimental group received tDCS to the occipital cortex in 12 sessions, 3 days per week.

The control group received sham stimulation to the occipital cortex in 12 sessions, 3 days per week.

This group was submitted to one evaluation session of cortical excitability.

tDCS involves application of very low amplitude direct current via surface scalp electrodes. The applied current modifies the transmembrane neuronal potential and thus influences the level of excitability. Depending on the polarity of active electrodes tDCS can increase or decrease the cortical excitability. The cathodal tDCS decrease the excitability, in this study a constant current of 2 mA intensity was applied for 20 min.

A 10-cm circular coil was used that has giving a peak magnetic field strength of 2 tesla. Subjects were asked to wear a blindfold, sit comfortably in a chair and to close their eyes to diminish ambient light.In sagittal line, three points were scored: 2, 3 and 4 cm above the inion. The single pulse transcranial magnetic stimulation was applied to one of the points scored and the subject was asked to report the presence or absence of a phosphene immediately after stimulation. The stimulation was repeated ten times at each intensity with a maximum frequency of 0.2 Hz, stimulation was initially applied to 60% of the maximum intensity of the stimulator. The intensity of stimulation was changed into blocks of 5% to minimum intensity that the subject can perceive the phosphene certainly, five times ten, then this value was set as the PT for migraineurs and controls.

Electroencephalography was performed by digital EEG equipment, the sampling rate of 500 Hz, 0.5 Hz high pass filter and low pass 35 Hz to capture brain electrical activity through 23 electrodes on the scalp according to the International 10-20 system.After positioning the electrodes, the subject remained comfortably seated and relaxed, but awake, with eyes closed 30 cm from the photic stimulator and, without any stimulation, EEG was collected for 1 minute (baseline).After the baseline, was collected a sequence of 1 minute record without stimulation followed by 3 seconds to 9 Hz photic stimulation. This sequence is repeated 4 times. After this procedure, the subject received trains of visual stimuli, 20 seconds each, at frequencies of 3, 9, 15, 21 and 27 Hz, 1 minute spaced from each other and totaling 12 minutes evaluation.