In a forested campus south of Liège, Steven Laureys studies vegetative patients in research that dates back decades. Working there as part of the Cyclotron Research Centre in the 1990s, he was surprised when PET brain scans revealed that the patients could respond to a mention of their own name: meaningful sounds produced a change in blood flow within the auditory primary cortices. Meanwhile, on the other side of the Atlantic, Nicholas Schiff was finding that within catastrophically injured brains lay partially working regions, clusters of remnant neural activity. What did it all mean?

At that time, doctors thought they already knew the answers: no patient in a persistent vegetative state was conscious. Never mind that staring at images made the brain light up, they carped: you can do that in a sedated monkey. Based on previous experience, a brain starved of oxygen as a result of a heart attack or a stroke was unlikely to recover if it didn’t in the first few months. These patients had suffered a fate that many people regarded as worse than death itself: they were functionally brainless. Undead. Doctors, with the best intentions, thought it was perfectly acceptable to end the life of a vegetative patient by starvation and the withdrawal of water. This was the age of what Laureys calls “therapeutic nihilism”.

What Owen, Laureys and Schiff were proposing was a rethink of some of the patients who were considered vegetative. A few of them could even be classed as being fully conscious and locked-in. The establishment was doggedly opposed. “You cannot imagine the environment in the late 1990s,” says Schiff. “The hostility we encountered went well beyond simple scepticism.” Looking back, Laureys pauses and smiles thinly: “Medical doctors do not like to be told they are wrong.” Schiff, Laureys and Owen cut lonely and isolated figures at academic conferences, desperately trying to explain their findings to their peers, who remained unconvinced, even antagonistic. The trio’s ideas were condemned as a waste of time.

Then came 2006. Owen and Laureys were trying to find a reliable way to communicate with patients in a vegetative state, including Gillian*. In July 2005, this 23-year-old had been crossing a road, chatting on her mobile phone. She was struck by two cars. Yet, though she had been diagnosed as vegetative, there was something about her that caught the attention of Martin Coleman of the University of Cambridge Impaired Consciousness Research Group, who submitted her for study by Owen.

Five months later, a strange stroke of serendipity allowed Gillian to unlock her box. The key arose from a systematic study Owen started with Laureys in 2005. They had asked healthy volunteers to imagine doing different things, such as singing songs or conjuring up the face of their mother. Then Owen had another idea. “I just had a hunch,” he says. “I asked a healthy control to imagine playing tennis. Then I asked her to imagine walking through the rooms of her house.” Imagining tennis activates part of the cortex, called the supplementary motor area, involved in the mental simulation of movements. But imagining walking around the house activates the parahippocampal gyrus in the core of the brain, the posterior parietal lobe, and the lateral premotor cortex. The two patterns of activity were as distinct as a ‘yes’ and a ‘no’. So, if people were asked to imagine tennis for ‘yes’ and walking around the house for ‘no’, they could answer questions via fMRI.

Gazing into Gillian’s ‘vegetative’ brain with the brain scanner, he asked her to imagine the same things – and saw strikingly similar activation patterns to the healthy volunteers. It was an electric moment. Owen could read her mind.

Gillian’s case, published in the journal Science in 2006, made front-page headlines around the world. The result provoked wonder and, of course, disbelief. “Broadly speaking, I received two types of email from my peers,” says Owen. “They either said ‘This is amazing – well done!’ or ‘How could you possibly say this woman is conscious?’”

As the old saw goes, extraordinary claims require extraordinary evidence. The sceptics countered that it was wrong to make these ‘radical inferences’ when there could be a more straightforward interpretation. Daniel Greenberg, a psychologist at the University of California, Los Angeles, suggested that “the brain activity was unconsciously triggered by the last word of the instructions, which always referred to the item to be imagined”.

Parashkev Nachev, a neurologist now at University College London, says he objected to Owen’s 2006 paper not on grounds of implausibility or a flawed statistical analysis but because of “errors of inference”. Although a conscious brain, when imagining tennis, triggers a certain pattern of activation, it does not necessarily mean that the same pattern of activation signifies consciousness. The same brain area can be activated in many circumstances, Nachev says, with or without any conscious correlate. Moreover, he argues that Gillian was not really offered a true choice to think about playing tennis. Just as a lack of response could be because of an inability to respond or a decision not to cooperate, a direct response to a simple instruction could be a conscious decision or a reflex. Nachev says that he is weary of stating, as he has time and again to the media, that profound conceptual issues with the techniques used to redefine this penumbra of consciousness remain unresolved.

What is needed is less philosophising and more data, says Owen. A follow-up study published in 2010 by Owen, Laureys and colleagues tested 54 patients with a clinical diagnosis of being in a vegetative state or a minimally conscious state; five responded in the same way as Gillian. Four of them were supposedly in a vegetative state at admission. Owen, Schiff and Laureys have explored alternative explanations of what they observed and, for example, acknowledge that the brain areas they study when they interrogate patients can be activated in other ways. But the 2010 paper ruled out such automatic behaviours as an explanation, they say: the activations persist too long to signify anything other than intent. Owen is grateful to his critics. They spurred him on, for instance to develop a method for asking patients questions that only they would know how to answer. “You cannot communicate unconsciously – it is just not possible,” he says. “We have won that argument.”

Since Owen’s 2006 Science paper, studies in Belgium, the UK, the USA and Canada suggest that a significant proportion of patients who were classified as vegetative in recent years have been misdiagnosed – Owen estimates perhaps as many as 20 per cent. Schiff, who weighs up the extent of misdiagnosis a different way, goes further. Based on recent studies, he says around 40 per cent of patients thought to be vegetative are, when examined more closely, partly aware. Among this group of supposedly vegetative patients are those who are revealed by scanners to be able to communicate and should be diagnosed as locked-in, if they are fully conscious, or minimally conscious, if their abilities wax and wane. But Schiff believes the remainder will have to be defined another way altogether, since being aware does not necessarily mean being able to use mental imagery. Nor does being aware enough to follow a command mean possessing the ability to communicate.

In 2009, Laureys’s team asked one of the original group of 54 patients that he and Owen had studied – patient 23 – a series of yes-or-no questions. It was the usual drill: imagine playing tennis for yes, navigating the house for no. The Liège patient, who had been in a vegetative state for five years, was able to answer five of six questions about his earlier life – and all of those were correct. Had he been on holiday to a certain place prior to his injury? Was such-and-such his father’s name? It was an exciting moment, said Laureys. “We were stunned,” adds Owen, who helped independently score the tests. “By showing us that he was conscious and aware, patient 23 moved himself from the ‘do not resuscitate’ category to the ‘not allowed to die’ category. Did we save his life? No. He saved his own life.”