A completely locked-in state is a condition that turns a person's body into their prison. They can't move any of their muscles -- even blink an eye, or lift a fingertip -- yet they remain completely mentally active.
Their memories, emotions, and cognitive abilities are unchanged, but without the ability to speak, move their eyelids, or use sign language, they can no longer communicate to the outside world. They must live inside their heads, trapped in an unresponsive, paralysed body.
A similar condition, locked-in syndrome, was made famous by the film The Diving Bell and the Butterfly, the memoir of a journalist who was left only able to move one of his eyelids after a massive stroke. The movement in his one eye allowed him to dictate the book the film is based on, and since then, eye-tracking technology has developed to the extent that those with locked-in syndrome can spell out words and phrases by moving their eyes from one letter to another displayed on a screen.
Until recently, those with completely locked-in syndrome were denied the same ability to communicate. Without eye movement, they couldn't use the tracking technology. But thanks to the work of a Swiss research institute, the Wyss Center, those with completely locked-in syndrome are beginning to express themselves to others.
The Wyss Center has developed a brain-computer interface that allows someone with completely locked-in syndrome to respond to the questions they are asked just by using their thoughts.
So how does the system work? The individual with completely locked-in syndrome wears a cap covered in NIRS optodes -- sensors that use lasers to measure the metabolic activity of the brain. When they're asked a question that requires a yes or no answer, the bit of their brain associated with that answer will work harder, demanding more oxygen from their blood, and blood flow and oxygen delivery to that region will increase.
The system measures how much blood is being delivered to one area compared to another using functional near-infrared spectroscopy (fNIRS), and turns it into an image which researchers and medical staff can understand. By asking someone in the completely locked-in state a question while they're wearing the sensor cap and then watching which areas of their brain light up, researchers know whether the individual is saying yes or no.
The Wyss Center system was piloted on four people with amyotrophic lateral sclerosis (ALS), a condition also known as motor neurone disease or Lou Gehrig's disease, which causes people to progressively lose the ability to move muscles until they reach a completely locked-in state. The ALS patients were asked a series of yes/no questions and instructed to think of the correct answer -- for example, 'Is Paris the capital of the US?' -- so researchers could delineate the area of the brain corresponding to a positive or negative response.
While the yes/no areas are found in the same part of the brain for each person, the homegrown analytics package developed by the Wyss Center can be trained to recognise the signature shape of area that each patient has.
The software "first decides whether the difference in the shape of the 'yes' and the 'no' response in the brain is clearly different, and only if it's clearly significantly different then the computer gives you a message that this is reliable 'yes' or a reliable 'no'," Professor Niels Birbaumer, the Wyss Center's lead researcher on the project, told ZDNet."
"However, it is different for each patient. When I think a 'yes' and when you think a 'yes', the shape of that thought is very different for each of us," he explained.
Once the system is adapted to the individual that will go on to use it, friends, carers, and medical professionals can ask the user closed yes/no questions and get a response. Some of the key questions that medical professionals asked were whether the ALS patients were happy and whether they wished their medical treatment to continue -- and received some unexpected answers.
"What is always surprising for us and for the family is that the quality of life in these people is very high, and there's no reason to assume that this disease and this state is causing depression and it's not worth living with such a disease. Our patients teach us this is not the case," Birbaumer said.
The system is been shrunk down to a manageable 5 to 7kg, and can be used for patients at home to be able to communicate their wishes; it's already being funded by health insurance companies in Germany.
The ability to answer yes/no questions opens up a massive set of possibilities for those in a completely locked-in state, but a more rich way to communicate -- responding to open-ended questions with more than a simple 'yes' or 'no' -- would be more beneficial still for such patients.
Reaching that stage of communication using brain-computer interfaces might, however, be more than a matter of better technical and medical knowledge: it may be a question of the nature of human thought itself.
It's been suggested that much of human thinking is goal-orientated: go here, do this, speak to that person, like this. But for somebody that's completely paralysed, finding such goals is all but impossible, and their cognition will change accordingly. That means researchers may have to recalibrate their ideas of which areas of the brain are the right ones to express the kind of more detailed ideas and responses someone may wish to communicate.
"If you have thought 100 times, 'I want to have something to eat' or 'I want to see this person' and you cannot achieve this, you stop that and you look for an alternative," Birbaumer said.
"It is possible the completely locked-in state abolishes voluntary complicated, goal-directed thinking and it needs a much stronger attentional force to think a goal-directed thought than a reflexive thought where you can give a quick answer... maybe you give up this goal-directed thinking. That doesn't mean you completely give up thinking, but you think in a non-voluntary manner. That's why it's so difficult to communicate in a non-voluntary way, but we hope we can change this."
One day, that richer communication may be possible through a hybrid system that combines both metabolic and electrical information, and one which can measure the periods when the user's attention is at its highest. In future, researchers may also seek to amplify communication signals in those in a completely locked-in state by implanting electrodes directly into user's brains, something that the Wyss Center has so far avoided due to the increased risk of infection that surgery poses to paralysed patients.
There's also hope that the system could be adapted to be used by patients with other conditions that impair communication, such as brain damage, to allow them to express their wishes once again -- because, said Birbauer, "a life without communication is not a real life".