Direct current brain polarization

The transcranial application of weak direct current (DC) to the brain is an effective neuromodulation technique that has had more than a century of experimental and therapeutic use. Focal DC brain polarization is now undergoing renewed interest, because of the wide acceptance of TMS as a research tool and candidate treatment for brain disorders. The effects of static electrical fields on cortical neurons in vivo have been known since the advent of intracellular recording. These effects are highly selective for neurons oriented longitudinally in the plane of the electric field. DC can enhance cognitive processes occurring in the treated area. The earliest clinical application of DC polarization was in the field of mood disorders. However, due to lack of temporal and spatial resolution, this technique does not appear particularly useful for exploring neurophysiological mechanisms.