Transcranial direct current stimulation (tDCS) is a non‑invasive method of electrical stimulation of the brain using a weak direct current applied to the scalp through electrodes. The aim is to modify cortical excitability and activity in the brain areas under the scalp electrodes. It is thought to work by the depolarisation and hyperpolarisation of cortical neurons.
The patient, who remains awake and alert during the procedure, is usually seated while a portable battery‑operated stimulator delivers a constant low‑strength direct current to 2 saline‑soaked sponge electrodes placed on the scalp. Treatment sessions typically last for about 20–30 minutes, and are repeated daily for several weeks. Treatment is usually delivered by a trained clinician, but it can also be self-administered by the patient. tDCS may be used alone or in addition to other treatments for depression.