A Canadian crash victim, who was thought to have been in a vegetative state for more than a decade, has told scientists through the power of thought that he is not in pain.
Scott Routley proved he is concious and aware of his surroundings after he communicated with researchers through a brain scan.
It is the first time a severely brain damaged patient has been able to provide clinically relevant information to doctors.
British neuroscientist Professor Adrian Owen, who leads the research team at the Brain and Mind Institute of Western Ontario, told a BBC Panorama programme to be broadcast tonight:
Mr Routley, from London, Ontario, suffered traumatic brain injuries when his car collided with a police vehicle - he was assumed to have been in a vegetative state for more than 12 years.
Vegetative state patients are not aware of their surroundings or capable of conscious thought.
Neurologist Professor Bryan Young, from University Hospital in London, Ontario, who has cared for Mr Routley for 10 years said the findings overturned previous assessments of the crash victim's condition.
Another of Prof Owen's patients - road accident victim Steven Graham - was asked whether he knew about his two-year-old niece Ceili.
Mr Graham answered "yes" to the question which showed he was able to create and store memories as she was born after his accident.
Prof Owen has previously shown that nearly one in five vegetative patients may in fact be conscious.
The programme, "The Mind Reader: Unlocking My Voice", airs tonight at 10.35pm on BBC One.
How scientists communicate with vegetative patients:
Prof Owen's team uses functional magnetic resonance imaging (fMRI) brain scans to detect hidden awareness in patients.
The scans produce images of "active" regions of the brain.
Patients are asked to imagine walking around their home or playing tennis - two thought processes that produce distinct patterns of activity in different parts of the brain.
By monitoring the activity on the brain scanner, the researchers can ask yes or no questions - one type of brain activity is taken as "yes" the other as "no".