Researchers in Belgium have developed a technique that allows coma patients that are in a minimally-conscious state to become aware enough to communicate — for up to a week — using mild electrical stimulation to their brains.

Building on the results of a 2014 study that showed that electrical stimulation of the brain could briefly help raise the state of awareness in coma patients, a research team from Belgium’s University of Liège performed a similar experiment using longer sessions, where 16 participants, either in a minimally conscious or vegetative state, were given 20-minute treatments for five days.

Coma patients that show signs of arousal, but lack apparent awareness, are said to be in a vegetative state, while those that show some signs of awareness but aren’t able to communicate are classified as minimally conscious.

In the previous experiment, the effects only lasted for a few hours, before the participants that responded lapsed back into their uncommunicative state; in the new study, nine of the participants responded to the stimulation, and were able to respond to commands, recognize objects, and even exhibit voluntary motor control. And, the effects lasted for a minimum of a week, as opposed to just a few hours, as had been the case in the previous study.

The technique uses what is called transcranial direct current stimulation (tDCS), meaning that the electrodes are simply placed on the scalp, rather than having to interact directly with the brain itself. Unlike electro-convulsive therapy, tDCS uses a mild current of just a few milliamps, to encourage the affected neurons to fire. In each of the patients, the stimulation was applied to the prefrontal cortex, an area involved in consciousness, but perhaps more importantly it is also linked to other vital centers, like the thalamus, an area that helps propagate electrical impulses to other areas of the brain.

Two of the participants were even able to respond to direct questions: "They couldn’t speak but we could ask questions, such as "is your name David?" and they answered yes or no by moving a part of their body, like their tongue or their foot," explains Aurore Thibaut, who led the study. "They correctly answered all of the questions we asked."

"This is an encouraging development," explains John Whyte, director of the Moss Rehabilitation Research Institute in Pennsylvania. "The study suggests that longer treatment intervals lead to more sustained improvements in consciousness." While more research is needed to determine the long-term effectiveness of the treatment, if successful, the lack of invasiveness involved in such a treatment means that it could be applied to coma patients receiving home care by their families, using comparatively inexpensive equipment.