Ride For Life

HANS-PETER SALZMANN wrote 265 words of this article. That contribution took him a surprisingly long time: something like 10 hours of intense concentration working a machine that is unimaginably difficult to control. Most people who try using it simply give up. And that's exactly why his voice -- and the voice of others in a similar situation -- needs to be heard.

Salzmann was 32 and working as a lawyer in Stuttgart when, in 1989, he was diagnosed with Lou Gehrig's disease, amyotrophic lateral sclerosis (ALS). This disease, which affects between 1.5 and 2 in 100,000 people, gradually destroys all voluntary movement, locking the intact mind into a paralysed body. Four years later, no longer able even to breathe for himself, Salzmann was fitted with an artificial respirator. He shows no self-pity. "It is bad luck that I got this illness," he says. "Like everybody else, I try to make the best of it, which isn't always easy and from time to time can be a real struggle. In spite of that, I try to have a good time, which I do quite successfully."

The key to this positive outlook, he says, is communication:it is his only freedom. But it doesn't come easy. Salzmann wrote the words above by using his brain's electrical activity to instruct a machine to spell. Known as the Thought Translation Device (TTD), the machine uses two electrodes stuck to his scalp to measure an electrical signal produced in the brain's cortex immediately before a thought or action. These signals are fed into a computer: by manipulating his thoughts to cause shifts in the signals' amplitude, Salzmann can move a cursor to select one of two halves of the alphabet, which appear successively in the bottom half of the screen. His cursor starts off in the top half. If he can see the letter he wants, he moves the cursor down to the lower half of the screen. If it doesn't contain the letter he wants, he must clear his thoughts to prevent the cursor moving, and thus reject the letters on offer. Each time he chooses, the bank of remaining letters divides again. Eventually, he is left with just the letter he wants.

It's a slow and difficult exercise, and requires immense control over his thoughts. "The process is divided into two phases," Salzmann says. "In the first phase, when the cursor cannot be moved, I try to build up tension with the help of certain images, like a bow being drawn or traffic lights changing from red to yellow. In the second phase, when the cursor can be moved, I try to use the tension built up in the first phase and kind of make it explode by imagining the arrow shooting from the bow or the traffic lights changing to green. When both phases are intensely represented in my head, the letter is chosen. When I want to not choose a letter, I try to empty my thoughts."

Salzmann began training with the TTD in 1996. First he practised on a simple computer game, trying to move the cursor towards fixed goals. After a few weeks, when he could hit the designated goal 80 per cent of the time, he graduated to the spelling programme. To begin with, his progress was agonisingly slow. It took him 16 hours to compose a message of 400 characters. Now, on a good day, he can do it in three. After two years, he wrote his first letter, thanking the scientists who built the device.

Salzmann was the first person to master the TTD. The machine, which is the brainchild of Niels Birbaumer, a medical psychologist at the University of T bingen in Germany, remains the brain-computer interface most widely tested in humans: 15 severely paralysed patients have worked with it. But it seems the TTD is not the final answer for locked-in patients. Of those 15 users who are still alive, a high proportion have failed to reach the threshold at which they are deemed proficient enough to use it for communication. Even a successful patient can perform erratically, taking anywhere between 20 seconds and six minutes to select a letter. Even Salzmann, who helped with the machine's development, still has days when he hits a mental trough; he doesn't know why this happens.

Finding technological fixes that could make using the TTD more intuitive and quicker to learn is not going to be easy, Birbaumer says. In any case it might be a a waste of effort: he has identified another, possibly more urgent problem for researchers to address. Last year Birbaumer and his colleagues issued a solemn warning to their peers. The field of brain-computer communication, they said, is "doomed to failure" unless researchers realise that psychological theory and experimentation are as important as the technical aspects of development (Psychological Bulletin, vol 127, p 358).

According to Birbaumer, the main stumbling block is that nobody has researched what paralysed patients use this form of communication for -- what rewards exist for them in their generally impoverished social environments. "You have to analyse, before you start, whether there is anybody around who is listening," he says. "If you are isolated, or the family is not really interested and the doctors are not interested, it doesn't make any sense to communicate."

Such a situation, he believes, will dictate whether an individual is willing to make the immense effort necessary to use a machine like the TTD. One of Birbaumer's terminally ill patients, for instance, gave up using the TTD. Having been locked-in for so long before learning to use it, he felt awkward contacting people with whom he had lost touch. "He communicated perfectly," says Birbaumer. "But after his wife left him and he had nobody to talk to, he stopped communicating. For one-and-a-half years now, he hasn't said a word."

A patient who has lost all family contact may still find socially rewarding activities, Birbaumer says, but these need to be planned so they have an incentive for learning to use the TTD. For one female patient they designed a project where she writes her biography and emails it to other patients, and gets feedback from them. "Not a lot, once or twice a month, but that is so rewarding that she decided to continue living," he says. Beforehand she hadn't seen any point. "Another male patient just likes to watch nude girls," he says. So they designed him an email-based programme whereby he can look at naked ladies as often as he likes. That, Birbaumer says, keeps him alive.

That's no exaggeration, he insists. The ability to interact with the world outside their bodies, in a way of their own choosing, is vital to locked-in patients . A sense of autonomy makes all the difference to how a patient perceives the quality of their life, and hence how they cope. A locked-in patient will always be dependent on someone to dress them, but with a communication device they can decide which clothes to wear. The first question one young woman asked when she had learned to use the TTD was, "Why do I wear such an ugly shirt?"

But communicating has to be rewarding for the patient: not too exhausting, restrictive or humiliating. Indeed, Birbaumer says, in this respect the TTD may not be ideal. It measures signals called the slow cortical potentials, a signal whose amplitude can be adjusted by mental effort. Birbaumer chose to use SCPs because they can be picked up from outside the skull and so there is no need for risky surgery. But the electrodes measure only the average activity of a large number of neurons that have different functions in the brain, and so you have to work up a technique for marshalling the thoughts that control those signals. That's a lot to ask. "You're taking a brain activity that you don't ordinarily command, and changing it into something that you can use to manipulate a computer cursor," says John Donoghue, a neuroscientist at Brown University in Rhode Island. "That's something you have to learn to do, like learning to play a musical instrument."

Another option, for some people at least, is exploiting residual muscle action. Something as tiny as the arching of an eyebrow or the direction of a glance can be roped in to control wheelchairs, household appliances or speech synthesisers. But this too has drawbacks. Partially paralysed patients who use their eyes to control such devices lose the freedom to look around. When your glance controls light switches, doors or your relationships with other people, you have to be careful. "Something that you ordinarily use in a natural way is now captured into this event," says Donoghue. "It's almost disabling."

Salzmann is aware of these issues: given another device to work with, he is able to communicate with his eyes, but it brings two big problems. "One is that my eye signs are difficult to read," he says. The other raises a less straightforward issue. "In this way, every word, every single letter becomes public. Despite the level of intimacy I have with the community workers and nurses, I feel the need to communicate some things without their knowing." This is where the TTD comes into its own. "The TTD is invaluable, as it enables me to write letters without anybody's help."

To make something like the TTD work for more people, Donoghue thinks the best option is to implant electrodes in the brain, a technique pioneered by Philip Kennedy at Emory University in Atlanta. Although brain surgery is risky, the implants can then pick up the impulses of individual neurons in the motor cortex where voluntary movements are generated. That means there's no need for a patient to learn an entirely new thought process or have one of their few freedoms restricted .

Birbaumer agrees that implantation of electrodes will ultimately be the only way to go with these brain-computer interfaces, but none of his patients are keen. "They say, 'well, I prefer sluggish, slow communication and no hole in my head'," he says.

And so, for the moment at least, Birbaumer's team are continuing to work on the TTD, but now only in close consultation with the users. They don't make any change, however useful it might seem to the developers, if it's not what the users want. The patients were offered the option of using their TTDs both for communication and to control their environment -- light switches and so on. But they all decided against it: for them, communication is paramount. The machine now incorporates a dictionary, a menu of frequently used phrases, and a specially adapted Web browser, complete with a secret password so that the user controls access.

This is of particular importance to Salzmann. "With the Internet I can read my favourite newspapers and search for books," he says. For him, privacy is everything. It might seem surprising for someone who has just escaped long years of silence to want to keep his thoughts private, but writing is something over which he has total control. It has become his greatest pleasure, and has perhaps contributed more than anything else to his remarkable attitude to a locked-in life. "In every extreme situation, you get to know yourself better," he says. "In my case, the moods have become more intense: the heights are higher, the lows are lower. Life is very fragile."

Clear thinking

Most brain-computer interfaces are so difficult to use because they involve directing brain activity that we normally have no control over. That's why John Donoghue, at Brown University in Rhode Island, is trying to tune into a more relevant brain signal. Evidence from studies using functional magnetic resonance imaging suggests that people use the same areas of their brain for imagining a movement as for making it. If a paralysed patient imagines moving their hand, the resulting activity could be used to move a cursor instead of a mouse or joystick.

Last year, Donoghue's group published its first results from trials on monkeys. They implanted 100 electrodes, each less than 2 millimetres long and a hair's breadth wide, into each monkey's motor cortex, which is where actions are planned. The signals were fed through an algorithm that translated them into cursor movements that were almost as fast and accurate as if the monkeys were controlling the cursor with their own hands. Ultimately, patients could use such a computer to control a prosthetic hand using the very neurons that guide hand movements in a healthy individual. Since it would be as natural as making the movement, says Donoghue, there would be no need for imagery or training.

This approach looks promising for humans, he says, even though the movements that can be translated through a robotic arm are still crude: they can just about manage the finger motion for picking up a cup without crushing it, say. More sophisticated demands, such as producing a piano chord, are some way off -- and direct communication even further. "To recreate speech from a speech area in the brain might be difficult," he says. "But one could imagine a way that you would type out the words and then have the computer produce the speech." Eventually, his aim is to read the activity of the brain's language areas and turn that directly into synthesised speech.

A life worth living

With improved life-support systems and intensive care, more and more patients are surviving life-threatening neurological onslaughts such as stroke and traumatic injury -- only to be left in a state of total or near total paralysis. For these patients, maintaining the will to live often depends on their ability to communicate.

"The day I started writing again professionally, my nurse was scared to death," wrote one contributor to a study on communications technology users with Lou Gehrig's disease. "Suddenly, my pulse was racing and my blood pressure was up. For the first year I was on the ventilator, all I did was watch TV. Being able to write again has given my life purpose, a reason to get up and get going every day."

With spinal cord injuries, a positive outlook can hasten a person's rehabilitation, says Paul Kennedy at Stoke Mandeville Hospital in Britain. "It is possible to manage the consequences reasonably well with appropriate support and a flexible frame of mind," he says. One of Kennedy's patients even says that being paralysed has improved his quality of life. He enrolled at university and went on to become a professor. "But for someone who is locked in, who can't communicate, it's a very, very difficult thing to overcome," Kennedy says.

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