Participants receive 40 minutes of DC polarization or sham polarization in each of two separate sessions. (No current is applied in the sham treatment). During the polarization, the patient rests quietly. Sponge pads that have been soaked in water are put on the left side of the head and above the right eye, and are held in place with elastic netting. Before the polarization and after about 20 minutes of polarization, patients undergo the following tests: