A comprehensive approach to understanding tDCS neurophysiological mechanisms

Transcranial direct current stimulation (tDCS) is a noninvasive neuromodulation method in which direct current is passed through scalp electrodes. Current flows through the scalp, skull and CSF before creating a weak electric field in the brain and causing membrane polarization in cortical neurons. Over the last 20 years, thousands of studies have highlighted wide ranging tDCS effects in healthy volunteers. tDCS is now under investigation as a potential treatment for addiction, depression and cognitive decline. However, the tDCS neurophysiological mechanism remains unknown. The aim of this project is to investigate and understand potential mechanisms which may be driving the tDCS effects observed in healthy volunteers. In addition to the neuromodulatory effects caused by direct polarization of cortical neurons, tDCS stimulates cranial and cervical nerves in the scalp that give input to the brain. Potential effects from this indirect tDCS neuromodulatory route have been overlooked. This project will combine healthy volunteer and animal experiments to investigate a range of tDCS mechanisms. Healthy volunteer experiments will use careful controls, such as pharmacological blockers, to probe and dissect the potential tDCS mechanisms. Animal electrophysiology experiments will investigate the validity of, and to provide insight into, the different potential mechanisms. The improved understanding of the tDCS mechanism will significantly advance the neuromodulation field.