The technique uses sonic stimulation to excite the neurons in the thalamus.
In a first, scientists in the US have used low-intensity ultrasound to successfully jump-start the brain of a 25-year-old man recovering from coma, an advance that may lead to a portable device that can non-invasively 'wake up' patients who are in vegetative state.
The technique uses sonic stimulation to excite the neurons in the thalamus, an egg-shaped structure that serves as the brain's central hub for processing information.
The patient has made remarkable progress following a treatment, researchers said.
"It's almost as if we were jump-starting the neurons back into function," said Martin Monti, from University of California, Los Angeles.
"Until now, the only way to achieve this was a risky surgical procedure known as deep brain stimulation, in which electrodes are implanted directly inside the thalamus," Martin Monti said.
"Our approach directly targets the thalamus but is noninvasive," he added.
Martin Monti cautioned that the procedure requires further study on patients before they determine whether it could be used consistently to help other people recovering from comas.
Researchers used a device about the size of a coffee cup saucer which creates a small sphere of acoustic energy that can be aimed at different regions of the brain to excite its tissue.
They placed it by the side of the man's head and activated it 10 times for 30 seconds each, in a 10-minute period.
Mr Monti said the device is safe because it emits only a small amount of energy - less than a conventional Doppler ultrasound.
Before the procedure began, the man showed only minimal signs of being conscious and of understanding speech - for example, he could perform small, limited movements when asked.
By the day after the treatment, his responses had improved measurably. Three days later, the patient had regained full consciousness and full language comprehension, and he could reliably communicate by nodding his head "yes" or shaking his head "no."
The technique targets the thalamus because, in people whose mental function is deeply impaired after a coma, thalamus performance is typically diminished.
Medications that are commonly prescribed to people who are coming out of a coma target the thalamus only indirectly.
The researchers plan to test the procedure on several more people.
If the technology helps other people recovering from coma, Mr Monti said, it could eventually be used to build a portable device - perhaps incorporated into a helmet - as a low-cost way to help "wake up" patients, perhaps even those who are in a vegetative or minimally conscious state.
Currently, there is almost no effective treatment for such patients, he said.
The research appears in the journal Brain Stimulation.