Figure 1.

Illustration of the measurement used for transcranial direct current stimulation (tDCS) electrode placement over the first dorsal interosseous muscle (FDI) hotspot, as determined by functional magnetic resonance imaging (fMRI). The antero-posterior distance of the M1 representation from the nasion was first measured after the subject's skull on the midline. The lateral component of the electrodes was then measured from the midline on each side. These measures were used to position the tDCS electrodes on the subject.