After undergoing transcranial direct current stimulation, patients in a minimally conscious state exhibited signs of increased awareness and even the ability to communicate. The effect didn't last long — but the insights gleaned could lead to more effective interventions.
Patients who are in a coma cannot move or respond to their environment. But a so-called vegetative state is a bit different; it's a type of coma in which people cannot fully emerge from unconsciousness. They often give the impression that they're pulling out from a coma, but they still lack true or full awareness. That said, brain scans show that some of these people have an inner life and are able to respond to their environment.
Unfortunately, doctors have had very little success trying to pull people out of such states. But in some cases, patients who were thought to be in an unrecoverable vegetative state were awakened after being administered a $5 over-the-counter sleeping pill called zolpidem. This pill seems to be invigorating brain cells that were once thought to be dead. But it now appears that low-level currents can do something similar.
Thanks to an experiment conducted at the University of Liège in Belgium, there may be hope in the form of mild electric shocks — or more accurately, transcranial direct current stimulation. Also known as tDCS, it's a form of neurostimulation that administers constant, low currents directly to the brain via small electrodes. It's typically used to help patients with brain injuries such as strokes. It can even improve math skills.
For the experiment, the researchers worked with 55 people who had experienced a traumatic brain injury or lack of oxygen to the brain. All were in a minimally conscious or vegetative state — some for as long as years.
During the 20 minute sessions of tDCS — which were aimed at areas responsible for memory, decision-making and awareness (i.e. the left dorsolateral prefrontal cortex) — 15 patients showed signs of increased awareness, including the ability to move their hands or follow instructions with their eyes. Remarkably, two patients were able to answer questions for two hours before drifting back into their previous state.
Indeed, for all patients, the effects lasted for just a couple of hours. And for most, the treatments yielded only moderate results.
"I don't want to give people false hope – these people weren't getting up and walking around – but it shows there is potential for the brain to recover functionality, even several years after damage," said Steven Laureys in a New Scientist article.
The researchers aren't exactly sure why it works, but they theorize that the stimulation boosts previously dormant brain activity over a threshold, thus enhancing processes involved in attention and working memory.
The team is now trying to figure out a way to prolong the effects.
Much more at New Scientist. The results of the experiment are set to appear in an issue of Functional Neurology.