tDCS mentioned only briefly in this in-depth article on vegetative state patients. How exciting that tDCS may prove to be a useful tool in determining brain state of patients.
The awareness network can be electrically roused. Laureys and his colleagues recently tested transcranial direct-current stimulation (tDCS), in which scalp electrodes are used to pass a weak direct current through the skull to alter the excitability of underlying brain tissue. The Liège team applied tDCS for 20 minutes to part of the mesocircuits of 55 people who were in a minimally conscious or vegetative state. They found that 15 showed glimmers of consciousness as a result. Some showed responses to commands, even though it was several years after they had been declared minimally conscious. Most dramatic, for two patients who had been declared minimally conscious a few months earlier, tDCS enabled them to nod or move their eyes in response to six questions.
The method offers a powerful way to probe which circuits have to be manipulated to awaken a silent brain. “In theory, at least, tDCS offers another way to reactivate circuits to help a damaged brain to recover some functionality, even several years after suffering severe damage,” Laureys explains.