A computational modelling study of transcranial direct current stimulation montages used in depression.

Transcranial direct current stimulation (tDCS) is a neuromodulatory technique which involves passing a mild electric current to the brain through electrodes placed on the scalp. Several clinical studies suggest that tDCS may have clinically meaningful efficacy in the treatment of depression. The objective of this study was to simulate and compare the effects of several tDCS montages either used in clinical trials or proposed, for the treatment of depression, in different high-resolution anatomically-accurate head models. Detailed segmented finite element head models of two subjects were presented, and a total of eleven tDCS electrode montages were simulated. Sensitivity analysis on the effects of changing the size of the anode, rotating both electrodes and displacing the anode was also conducted on selected montages. The F3-F8 and F3-F4 montages have been used in clinical trials reporting significant antidepressant effects and both result in relatively high electric fields in dorsolateral prefrontal cortices. Other montages using a fronto-extracephalic or fronto-occipital approach result in greater stimulation of central structures (e.g. anterior cingulate cortex) which may be advantageous in treating depression, but their efficacy has yet to be tested in randomised controlled trials. Results from sensitivity analysis suggest that electrode position and size may be adjusted slightly to accommodate other priorities, such as skin discomfort and damage.