fMRI Study of tES in Major Depression

The purpose of this research study is to understand how a kind of brain stimulation, called transcranial electrical stimulation (tES), affects brain function in people with major depression. tES delivers low electrical current to the head using electrodes applied to the skin, and is described as a "neuromodulation" or "neurostimulation" technique. This study uses a specific kind of tES called "transcranial direct current stimulation", or tDCS, where a constant (unchanging) electrical current is passed between two electrodes on the head. Neuromodulation methods like tES have shown promise in changing brain function, as well as treating some brain disorders like major depression. Yet, how tES brain function remains unclear. To better understand how tES works, the investigators will use MRI (a type of brain scan) to measure brain function during tES in people with major depression.