Professor Adrian Owen uses functional magnetic resonance imaging (fMRI) scans to detect changes in the flow of the blood around the brain.
Scott, from Ontario, Canada, and British patient Alex Seaman both feature in a BBC1 Panorama programme on the groundbreaking approach to brain-injured patients tonight.
First, patients are asked to imagine they are playing tennis. This prompts an increase in blood-flow to an area at the front of the brain called the premotor cortex, which can be detected by the scan.
Patients are then told to picture themselves walking around different rooms in their house. This activates an entirely separate area of the brain, the parahippocampal gyrus, situated in the middle.
They are then asked a question and told to imagine they are playing tennis if the answer is no and if yes, to pretend they are walking round the house.
From the subsequent changes in blood flow, doctors can work out their answers.
The technique has been successfully used on a number of vegetative patients at Addenbrookes Hospital in Cambridge and at the Brain and Mind Institute of Western Ontario in London, Canada.
Scott is the first to have been able to answer whether he was in pain. On two occasions in the last six months he has told doctors 'no' by imagining he was playing tennis. Until then patients had responded to basic questions such as 'is your father's name Alexander?' or 'do you have a niece?'
Doctors hope that over the coming weeks Scott will be able to answer questions such as what time he prefers to be bathed or given his dinner.
His family also want to know whether he likes listening to ice hockey on the radio.
"Scott has been able to show he has a conscious, thinking mind," Professor Owen said.
"We have scanned him several times and his pattern of brain activity shows he is clearly choosing to answer our questions. We believe he knows who and where he is."
Professor Bryan Young of University Hospital in London, Ontario, who has been Scott's neurologist for a decade, said: "He had the clinical picture of a typical vegetative patient - no emotional response, no fixation or following with his eyes. He didn't have any spontaneous movements that looked meaningful and I was quite impressed and amazed that he was able to show these cognitive responses with fMRI."
Not all vegetative patients can respond using this technique as it requires so much concentration. Professor Owen says that about one in five who have scans can answer questions.
- DAILY MAIL