A man who spent more than six years in a near-vegetative state after a horrific assault has made a dramatic recovery following a pioneering treatment to stimulate his brain with electrical pulses.

The 38-year-old American suffered devastating brain damage during a street robbery in 1999, leaving him almost completely unconscious and in need of round-the-clock care. Doctors who performed emergency surgery on the man told his parents that if he survived the operation, his chances of recovery were zero.

The man, who was confined to a bed in a specialised nursing home, very rarely opened his eyes, occasionally tried to mouth words and move his head, but was otherwise unable to communicate and had to be fed through a tube. Following the new treatment the patient, who cannot be named, is able to recognise and talk to his doctors and family, eat and drink normally and perform basic movements, such as brushing his hair.

It is the first time the technique, called deep brain stimulation, has been used to treat a patient in what neuroscientists refer to as a minimally conscious state. It is also the first clear sign that it may be possible to rehabilitate people with such severe brain damage that they have previously been considered untreatable by modern medicine. "He was beaten and kicked around his head, his skull was completely crushed and he was left for dead," the man's mother told a press conference by telephone. "The doctors said if your son pulls out of this in the next 72 hours, and we don't know if he will, he will be a vegetable for the rest of his life. You need to make a decision about what you want to do." The patient spent five years in a nursing home and his parents gave permission for him not to be resuscitated should his condition suddenly deteriorate.

In August 2005, a team of doctors from three hospitals in the US asked the family if they wished their son to join an experimental study to test the new technique, which involves implanting 1mm-wide electrodes into the two regions of the brain closely linked to consciousness. The technique is already used to stimulate other areas of the brain to control tremors in people with Parkinson's disease. Several trials are under way to test its effectiveness at treating severe depression, obsessive compulsive disorder, and epilepsy.

With the parents' agreement, the man was fitted with brain electrodes that fed into twin regions of the central thalamus and hooked up to a pacemaker implanted under the skin of the chest during a 10-hour operation. He was then treated with electrical pulses for 480 days.

The surgeons hoped that the electrical pulses might kickstart activity in his brain and reawaken intact brain circuits. The results, reported in the journal Nature, were rapid and astonishing.

"After deep brain stimulation, we immediately saw some changes, literally within the first day," said neurophysiologist Joseph Giacino, who led the post surgical team at the JFK Johnson Rehabilitation Institute in Edison, New Jersey.

At first, the man opened his eyes and was able to track people as they moved around the room. Later, he regained the ability to speak a few words at a time and make careful, intentional limb movements. He is now fitted with implants that stimulate his brain every 12 hours.

"My son can now speak, watch a movie without falling asleep, drink from a cup, express pain, he can cry and laugh ... He can say 'I love you mum'. I still cry every time I see my son, but they're tears of joy," his mother said.

Doctors expect to see continuing improvements in his recovery.

Ali Rezai, a neurosurgeon at the Cleveland Clinic Foundation, who led the team to place the electrodes, said: "When we first activated the pacemakers ... we looked at each other, the team humbled in many ways, but at the same time excited about the prospects and the potential of what can be done for these patients."

The team emphasise that the treatment might not work for all patients in a minimally conscious state. Estimates suggest up to 280,000 brain-damaged people may be in minimally conscious states in the US alone. Adrian Owen, who has studied patients in a vegetative state at the MRC cognition and brain sciences unit in Cambridge, said the case study was a "major step" toward treatment for others. "Clearly this suggests a possible treatment for some patients with MCS," he said.