Transcranial direct-current stimulation
Transcranial direct current stimulation (tDCS) is a form of neuromodulation that uses constant, low-intensity DC electricity delivered via electrodes placed along on the scalp. This type of neurotherapy was originally developed to help patients with brain injuries or neuropsychiatric conditions such as major depressive disorder.
Source: Wikipedia — Transcranial direct-current stimulation (CC BY-SA 4.0)