Transcranial direct current stimulation

From Wikipedia, the free encyclopedia

Transcranial direct current stimulation (tDCS) is the application of weak electrical currents (1-2 mA) to modulate the activity of neurons in the brain. Several generations of neurophysiological experiments have shown that neurons respond to static (DC) electrical fields by altering their firing rates. Firing increases when the positive pole or electrode (anode) is located near the cell body or dendrites and decrease when the field is reversed. However, when the electrodes are placed on the scalp, the current density produced in the brain is exceedingly small, changing membrane potentials only by a fraction of a millivolt. It is still under debate whether such small currents can cause noticeable effects.

In the 1960s, a few reasonably well-controlled experiments suggested that electrodes placed on the forehead can produce noticeable psychological changes that were dependent on the direction of the field. Recently, Michael A. Nitsche and colleagues at the University of Göttingen claimed that anodal polarization of the motor cortex increased the motor response of transcranial magnetic stimulation of the same area; reduction of this response was observed with cathodal polarization. Moreover, these effects were reported to last for an appreciable amount of time after exposure. Investigators are currently testing the validity of these claims and the effects of tDCS on other brain areas and functions.

DC brain polarization is not "stimulation" in the same sense as transcranial magnetic stimulation or the stimulation of the brain and nerves with conventional electrical techniques. It does not appear to cause nerve cell firing on its own and does not produce discrete effects such as the muscle twitches associated with classical stimulation. It is also important to distinguish it from electroconvulsive therapy, which is used to treat mental illnesses such as major depression by passing pulses of approximately 1 ampere into the brain in order to provoke an epileptic seizure. Currently tDCS is being studied for the treatment of a number of conditions including major depression.[1]


[edit] See also

tDCS is a weak electrical current of 1 or 2 m Ampere is applied to the head with an electrode. The electrode is a non-metalic conductive rubber electrode, covered completely by saline soaked sponges.It is a noninvasive brain stimulation technique that utilizes low amplitude direct currents applied via scalp electrodes to inject currents in the brain and thus modulates the level of excitability. It doesn't elicit seizures and it doesn't require anesthesia

[edit] References