Brain That Changes Itself: into the abyss
Added: Sun, 27 Jul 2008 23:00:00 UTC
Thanks to SPS for the link.
Brain That Changes Itself: into the abyss
Can a damaged brain change its own structure and learn to replace lost functions? Conventional neuroscience once said no, but pioneers in the field have achieved miraculous transformations. From his investigation of their work, Norman Doidge tells the story of the perpetually falling woman
Cheryl Schiltz feels like she is perpetually falling. And because she feels like she is falling, she falls. When she stands up without support, she looks as if she were on a precipice, about to plummet. First her head wobbles and tilts to one side and her arms reach out to try to stabilise her stance. Soon her whole body is moving chaotically back and forth, like a person walking a tightrope in that frantic see-saw moment before losing his balance - except that both her feet are firmly planted on the ground, wide apart. When she tries to walk she has to hold on to a wall, and still she staggers like a drunk.
For Cheryl there is no peace, even after she has fallen to the floor. I ask her, does the sense of falling go away once she has landed? 'There have been times,' Cheryl says, 'when I literally lose the sense of the feeling of the floor and an imaginary trapdoor opens up and swallows me.' Even when she has fallen, she feels that she is still falling, perpetually, into an infinite abyss.
Cheryl's problem is that her vestibular apparatus, the sensory organ for the balance system, does not work. Soon after her problem began, she lost her job as an international sales representative and now lives on a disability allowance of $1,000 a month. She has a new-found fear of growing old. And she has a rare form of anxiety that has no name.
An unspoken and yet profound aspect of our well-being is based on having a normally functioning sense of balance. The balance system gives us our sense of orientation in space. Its vestibular apparatus consists of three semi-circular canals in the inner ear that tell us when we are upright and how gravity is affecting our bodies by detecting motion in three-dimensional space. One canal detects movement in the horizontal plane, another in the vertical plane, and another when we are moving forwards or backwards. The signals from the vestibular apparatus go along a nerve to a specialised clump of neurons in the brain, the vestibular nuclei, which process them, then send commands to our muscles to adjust themselves.
I am with Cheryl, and Paul Bach-y-Rita, a leading pioneer in understanding brain 'plasticity', and his team at a lab in the University of Wisconsin Medical School. Yuri Danilov, a biophysicist, analyses data they are gathering. He says, 'Cheryl has lost her vestibular system - 95 to 100 per cent.'
By any conventional standard, Cheryl's case is hopeless. The conventional view sees the brain as made up of a group of specialised processing modules, genetically hard-wired to perform specific functions. Once one of them is this damaged, it cannot be replaced. Now that her vestibular system is affected, Cheryl has as much chance of regaining her balance as a person whose retina has been damaged has of seeing again.
But today all that is about to be challenged. She is wearing a construction hat with holes in the side and a device inside called an accelerometer. Cheryl licks a thin plastic strip with small electrodes on it, and places it on her tongue. The accelerometer and the tongue strip are connected to a computer. This machine, a bizarre-looking Bach-y-Rita prototype, will replace Cheryl's vestibular apparatus by sending balance signals to her brain from her tongue. It could end her nightmare.
In 1997, after a hysterectomy, Cheryl, then 39, contracted a post-operative infection and was given the antibiotic gentamicin. Excessive use of gentamicin is known to poison the inner ear structures and can be responsible for hearing loss (which Cheryl does not have), ringing in the ears (which she does), and devastation to the balance system. But because gentamicin is cheap and effective, it is still prescribed, though usually for only a brief time. Cheryl says she was given the drug way beyond the limit. And so she became one of a small tribe of gentamicin's casualties, known among themselves as Wobblers.
Suddenly one day she discovered that she could not stand without falling. She would turn her head, and the whole room would move. Finally she got to her feet by hanging on to a wall and reached for the phone to call her doctor. Hospital doctors did various tests - they poured freezing-cold and warm water into her ears and tilted her on a table. When they asked her to stand with her eyes closed, she fell over. It was then that a doctor told her, 'You have no vestibular function.' Tests showed she had about two per cent of the function left. 'He was,' Cheryl says, 'so nonchalant. "It looks like a side-effect of the gentamicin." Why in the world wasn't I told about that? "It's permanent," he said.'
Because the link between Cheryl's vestibular apparatus and her visual system is damaged, her eyes cannot follow movement smoothly. 'Everything I see bounces like a bad amateur video,' she says. Although she cannot track moving objects with her eyes, her vision is all she has to tell her that she is upright. Our eyes help us know where we are in space by fixing on horizontal lines. Once, when the lights went out, Cheryl immediately fell to the floor. But vision proves an unreliable crutch for her, because any kind of movement in front of her - even a person reaching out to her - exacerbates the falling feeling. Even zigzags on a carpet can topple her by initiating a burst of false messages that make her think she is standing crookedly.
'Let's begin,' Danilov says, adjusting the controls. Cheryl puts on the hat and closes her eyes. She leans back from the table, keeping two fingers on it for contact. She does not fall. She lifts her fingers from the table - and starts to cry. The sense of perpetual falling has left her for the first time in five years. Her goal today is to stand, free, for 20 minutes, with the hat on, trying to keep centred.
The jerking has stopped, and her brain is decoding signals from her artificial vestibular apparatus. For her these moments of peace are a miracle - a neuroplastic miracle, because somehow these tingling sensations on her tongue are making their way, through a novel pathway in the brain, to the area that processes balance.
'We are now working on getting this device small enough so that it is hidden in the mouth, like an orthodontist's mouth retainer,' Bach-y-Rita says. 'Then someone like Cheryl should be able to wear the apparatus, talk and eat without anyone knowing she has it.'
'It's time,' Danilov says, turning off the machine. Cheryl removes the tongue device and takes off the hat. She gives a big grin, stands free with her eyes closed, and does not fall. Then she opens her eyes and, still not touching the table, lifts one foot off the ground, so she is balancing on the other.
'I love this guy,' she says, and goes over and gives Bach-y-Rita a hug. 'I feel anchored and solid. I don't have to think where my muscles are. I can actually think of other things.' She returns to Danilov and gives him a kiss.
The first time they tried the hat, Cheryl wore it for only a minute. They noticed that after she took it off, there was a 'residual effect' that lasted about 20 seconds, a third of the time she wore the device. Then Cheryl wore the hat for two minutes and the residual effect lasted about 40 seconds. Then they went up to about 20 minutes, expecting a residual effect of just under seven minutes. But instead it lasted triple the time, a full hour.
Cheryl starts clowning and showing off. 'I can walk like a woman again. That's probably not important to most people, but it means a lot that I don't have to walk with my feet wide apart now.' 'What is amazing,' Danilov says, 'is that after some time on the device, she behaves almost normally. It is the recovery of the vestibular function.'
A few days later an email for Bach-y-Rita arrives from Cheryl, her report from home about how long the residual time lasted. 'Total residual time was: three hours, 20 minutes The wobbling begins in my head - just like usual I am having trouble finding words Swimming feeling in my head. Tired, exhausted Depressed.' On the other hand, three hours and 20 minutes after only 20 minutes on the machine is a residual time 10 times greater than the time on the device. She is the first Wobbler ever to have been treated, and even if the residual time never grows longer, she could now wear the device briefly four times a day and have a normal life. But there is good reason to expect more, since each session seems to be training her brain to extend the residual time. If this keeps up
It did keep up. Over the next year Cheryl wore the device more frequently to get relief and build up her residual effect, which progressed to multiple hours, to days, and then to four months. Now she does not use the device at all and no longer considers herself a Wobbler.
In 1969 the science journal Nature published a short article that had a distinctly sci-fi feel about it. Its lead author, Paul Bach-y-Rita, described a device that enabled people who had been blind from birth to see. All had damaged retinas and had been considered untreatable. The Nature article was reported in the New York Times, Newsweek and Life, but perhaps because the claim seemed so implausible, the device and its inventor soon slipped into relative obscurity. Accompanying the article was a picture of a machine - an old dentist's chair with a vibrating back, a tangle of wires and bulky computers. The whole contraption weighed 400lb.
A congenitally blind person - someone who had never had any experience of sight - sat in the chair, behind a large camera. He 'scanned' a scene in front of him by turning hand cranks to move the camera, which sent electrical signals of the image to a computer that processed and then conveyed them to 400 vibrating stimulators on a metal plate in the chair back resting against the blind subject's skin. The stimulators functioned like pixels, vibrating for the dark part of a scene and holding still for the brighter shades. This 'tactile-vision device', as it was called, enabled blind subjects to make out faces and shadows, and distinguish between objects that were close and far away.
Everyone who used the clunky machine had a remarkable perceptual experience, as they went from having tactile sensations to 'seeing' people and objects. With a little practice, the blind subjects began to experience the space in front of them as three-dimensional. It was one of the first and boldest applications of neuroplasticity - using one sense to replace another - and it worked.
Yet it was ignored because the scientific mind-set at the time assumed that the brain's structure is fixed, and that our senses, the avenues by which experience gets into our minds, are hardwired. This idea, which still has many adherents, is called 'localisationism'. Almost alone among his colleagues, Bach-y-Rita rejected localisationism. Our senses have an unexpectedly plastic nature, he discovered: if one is damaged another can sometimes take over in what he calls 'sensory substitution'. By discovering that the nervous system can adapt to seeing with cameras instead of retinas, Bach-y-Rita laid the foundation for retinal implants that can be surgically inserted into the eye.
Unlike most scientists, who stick to one field, Bach-y-Rita became an expert in many - medicine, psychopharmacology, ocular neurophysiology (the study of eye muscles), visual neurophysiology (the study of sight and the nervous system) and biomedical engineering. He speaks five languages and has lived in Italy, Germany, France, Mexico, Sweden and throughout the United States. After becoming a physician, he gave up medicine and switched to basic research. He asked questions that seemed to defy common sense, such as, are eyes necessary for vision, or ears for hearing? When he was 44 years old, he returned to medicine and began a residency in rehabilitation.
Unassuming and cerebral, Paul Bach-y-Rita is of Spanish and Jewish ancestry and grew up in the Bronx. He was 4ft 10in when he entered high school because of a mysterious disease that stunted his growth, and was twice given a preliminary diagnosis of leukaemia. He was bullied, and developed a high pain threshold. When he was 12 his appendix burst and the mysterious disease, a rare form of chronic appendicitis, was properly diagnosed. He grew eight inches and won his first fight.
Speaking at home in Madison, Wisconsin, he told me, 'I can connect anything to anything. We see with our brains, not with our eyes. When a blind man uses a cane he sweeps it back and forth, and has only one point, the tip, feeding him information through the skin receptors in the hand. Yet this sweeping allows him to sort out where the doorjamb is, or the chair, or distinguish a foot when he hits it, because it will give a little. Then he uses this information to guide himself to the chair to sit down. Though his hand sensors are where he gets the information and where the cane "interfaces" with him, what he perceives is not the cane's pressure on his hand but the layout of the room: chairs, walls, feet, the three-dimensional space. The receptor surface in the hand becomes merely a relay for information, a data port. The receptor surface loses its identity in the process.'
Bach-y-Rita determined that skin and its touch receptors could substitute for a retina, because both the skin and the retina are two-dimensional sheets, covered with sensory receptors that allow a 'picture' to form on them.
It is one thing to find a new data port, or way of getting sensations to the brain, but another for the brain to decode these skin sensations and turn them into pictures. To do that, the brain has to learn something new. This adaptability implies that the brain is plastic, in the sense that it can reorganise its sensory perceptual system.
If the brain can reorganise itself, simple localisationism cannot be a correct image of the brain. Serious localisationism was first proposed in 1861 when Paul Broca, a surgeon, had a stroke patient who lost the ability to speak and could utter only one word. No matter what he was asked, the poor man responded, 'Tan, tan.' When he died, Broca dissected his brain and found damaged tissue in the left frontal lobe. Sceptics doubted that speech could be localised to a single part of the brain until Broca showed them the injured tissue, then reported on other patients who had lost the ability to speak and had damage in the same location. That place came to be called 'Broca's area' and was presumed to coordinate the movements of the muscles of the lips and tongue. Soon afterwards another physician, Carl Wernicke, connected damage in another brain area further back to a different problem: the inability to understand language. Over the next 100 years localisationism became more specific as new research refined the brain map.
Bach-y-Rita came to doubt localisationism while in Germany in the early 1960s. He had joined a team that was studying how vision worked by measuring with electrodes electrical discharges from the visual processing area of a cat's brain. The team fully expected that when they showed the cat an image, the electrode in its visual processing area would send off an electric spike, showing it was processing that image. And it did. But when the cat's paw was accidentally stroked, the visual area also fired. And they found that the visual area was also active when the cat heard sounds.
Bach-y-Rita began to think that the localisationist idea of 'one function, one location' could not be right. The 'visual' part of the cat's brain was processing at least two other functions, touch and sound. He began to conceive of much of the brain as 'polysensory' - that its sensory areas were able to process signals from more than one sense.
Over the next few years Bach-y-Rita began to study all the exceptions to localisationism and began to argue that 'a large body of evidence indicates that the brain demonstrates both motor and sensory plasticity.' One of his papers was rejected for publication six times by journals, not because the evidence was disputed but because he dared to put the word 'plasticity' in the title. Yet Bach-y-Rita persisted and began, in a series of books and several hundred articles, to lay out the evidence for brain plasticity and to develop a theory to explain how it might work.
The origin of Bach-y-Rita's understanding of brain rehabilitation lies in the dramatic recovery of his own father, the Catalan poet and scholar Pedro Bach-y-Rita, after a disabling stroke. In 1959 Pedro, then a 65-year-old widower, had a stroke that paralysed his face and half of his body and left him unable to speak. Paul's brother George, now a psychiatrist in California, was told that his father had no hope of recovery and would have to go into an institution. George, then a medical student in Mexico, brought his paralysed father from New York, where he lived, back to Mexico to live with him. At first he arranged rehabilitation for his father at the American British Hospital, which offered a typical four-week rehab. After four weeks his father was still helpless and needed to be lifted on and off the lavatory and showered. 'Fortunately, he was a little man, 118lb, and we could manage him,' George says.
George knew nothing about rehabilitation, and his ignorance turned out to be a godsend, because he succeeded by breaking all its rules. 'I decided that instead of teaching my father to walk, I was going to teach him first to crawl. We got kneepads for him. At first we held him on all fours, but his arms and legs didn't hold him very well, so it was a struggle.' As soon as Pedro could support himself somewhat, George got him to crawl with his weak shoulder and arm supported by a wall. 'That crawling beside the wall went on for months. The only model I had was how babies learn. So we played games on the floor, with me rolling marbles and him having to catch them. Everything we tried involved turning normal life experiences into exercises. We turned washing up into an exercise. He'd hold a pot with his good hand and make his weak hand - it had little control and made jerking movements - go round and round, 15 minutes clockwise, 15 minutes anticlockwise.' The circumference of the pot kept his hand contained. The regime took many hours every day, but gradually Pedro went from crawling to moving on his knees, to standing, to walking.
Pedro struggled with his speech on his own, and after about three months there were signs it too was coming back. After a number of months he wanted to resume writing. He would sit in front of the typewriter, his middle finger over the desired key, then drop his whole arm to strike it. Eventually he learnt to type normally again.
At the end of a year his recovery was complete enough for Pedro to start full-time teaching again at City College in New York, working there until he retired at 70. Then he got another teaching job at San Francisco State, remarried, and kept working, hiking and travelling. He was active for seven more years after his stroke. On a visit to friends in Bogotá, Colombia, he went climbing high in the mountains. At 9,000 feet he had a heart attack and died shortly after. He was 72.
I asked George if he understood how unusual this recovery was so long after his father's stroke and whether he thought at the time that the recovery might have been the result of brain plasticity. 'I just saw it in terms of taking care of Papa. But Paul, in subsequent years, talked about it in terms of neuroplasticity.'
Pedro's body was brought to San Francisco, where Paul Bach-y-Rita was working. In those days, before brain scans, post-mortems were routine because they were one way doctors could learn about brain diseases, and about why a patient died. Paul asked Dr Mary Jane Aguilar to perform the autopsy. 'A few days later Mary Jane called me and said, "Paul, come down. I've got something to show you." There, spread out on the table, were slices of my father's brain on slides.
'I was feeling revulsion, but I could also see Mary Jane's excitement, because what the slides showed was that my father had had a huge lesion from his stroke and that it had never healed, even though he recovered all those functions. I was thinking, "Look at all this damage." And she said, "How can you recover with all this damage?"?'
When he looked closely, Bach-y-Rita saw that his father's seven-year-old lesion was mainly in the brain stem - the part of the brain closest to the spinal cord - and that other major brain centres in the cortex that control movement had been destroyed by the stroke as well. Ninety-seven per cent of the nerves that run from the cerebral cortex to the spine were destroyed - catastrophic damage that had caused his paralysis.
'I knew that meant that somehow his brain had totally reorganised itself with the work he did with George. We didn't know how remarkable his recovery was until that moment, because we had no idea of the extent of his lesion, since there were no brain scans in those days. When people did recover, we tended to assume that there really hadn't been much damage in the first place.'
His father's story was first-hand evidence that a 'late' recovery could occur even with a massive lesion in an elderly person. His father's 'late recovery' triggered a career change for Bach-y-Rita. He turned his attention to treating strokes, focusing on late rehabilitation, helping people overcome major neurological problems years after they had begun, and developing computer video games to train stroke patients to move their arms again. And he began to integrate what he knew about plasticity into exercise design. Traditional rehabilitation exercises typically ended after a few weeks when a patient stopped improving, or 'plateaued'. But Bach-y-Rita, based on his knowledge of nerve growth, began to argue that these learning plateaus were temporary - part of a plasticity-based learning cycle in which stages of learning are followed by periods of consolidation. Though there was no apparent progress in the consolidation stage, biological changes were happening internally, as new skills became more automatic and refined.
Bach-y-Rita developed a programme for people with damaged facial motor nerves, who could not move their facial muscles and so could not close their eyes, speak properly or express emotion. He had one of the 'extra' nerves that normally goes to the tongue surgically attached to a patient's facial muscles. Then he developed a programme of brain exercises to train the 'tongue nerve' (and particularly the part of the brain that controls it) to act like a facial nerve.
These patients learnt to express normal facial emotions, speak and close their eyes. Thirty-three years after Bach-y-Rita's Nature article, scientists using the small modern version of his tactile-vision machine have put patients under brain scans and confirmed that the tactile images that enter patients through their tongues are indeed processed in their brains' visual cortex.
Cheryl Schiltz has not been the only one to benefit from Paul Bach-y-Rita's strange hat. The team has since used the device to train 50 more patients to improve their balance and walking. Some had the same damage Cheryl had; others have had brain trauma, stroke or Parkinson's disease. Bach-y-Rita's importance lies in his being the first of his generation of neuroscientists both to understand that the brain is plastic and to apply this knowledge in a practical way to ease human suffering.
When Cheryl's brain developed a renewed vestibular sense - or blind subjects' brains developed new paths as they learnt to recognise objects, perspective or movement - these changes were not the mysterious exception to the rule but the rule: the sensory cortex is plastic and adaptable. But our brains also restructure themselves in response to input from the simplest tools, too, such as a blind man's cane. The brain is a far more open system than we ever imagined, and nature has gone very far to help us perceive and take in the world around us. It has given us a brain that survives in a changing world by changing itself.
# Extracted from 'The Brain That Changes Itself', by Norman Doidge (Penguin), published on August 12 and available for £9.99 from Telegraph Books (0870-428 4112; books.telegraph.co.uk)
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