On tickling brains to investigate minds.

Stimulating the brain by either direct or eddy electrical currents for medical and research purposes has a long history. One of the first records dates back to 43AD and is attributed to Scribonius Largus, physician of the Roman Empire, who reported the treatment of migraines and headache through application of electrical currents with the torpedo fish. In the 15th century, Paracelsus suggested that magnetic forces can promote self-healing, and in the 18th century French physician Charles Le Roy started to experiment with electricity as a means to influence psychological function. Although he did not succeed in restoring vision to a blind patient by winding conducting wires around the patient’s head, he did manage to make him perceive vivid flashes of light (phosphenes). Noninvasive electrical stimulation, however, was associated with painful sensations and continued to be the main stimulation device for experimental and medical treatments even after the discovery, in the first half of the 19th century by Michael Faraday, that a changing magnetic field can induce an electric current in a conducting means. It was only with JacquesArsène d’Arsonval, at the end of the 19th century, and Silvanus Thompson at the beginning of the 20th, that the idea of using magnetic stimulation to induce eddy currents in the brain came to light, its majestic progression made possible by Anthony Barker and collaborators who, in 1976, started to develop the first reliable magnetic stimulator. In 1985 it was formally introduced as a modulator of brain function. Magnetic stimulators have now become widely available in both clinical as well as research institutions. Transient side effects may include headache, neck ache and mild discomfort, but these are secondary effects not directly related to the cortical stimulation itself. A more serious concern is the