On 8 March 1969, an extraordinary experiment was reported in the pages of Nature, Europe's leading science journal. It involved a group of people who took turns to sit in an old dentist's chair and describe the room around them. They commented on the presence of a phone on the table, a nearby vase, people's expressions and how they wore their hair. It was remarkable because all were completely blind.

The scientific establishment took a dim view of the work and, for the most part, dismissed it as implausible. But today it stands as one of the first, and most striking, demonstrations of neuroplasticity, the brain's ability to adapt. The blind people had learned to "see" through the sensation of touch.

Here's what happened. The back of the chair had been fitted with hundreds of tiny stimulators that were hooked up to a video camera. As the camera panned the room, those in the chair felt tiny vibrations that seemed to dance across their skin as the image moved. With practice, the blind volunteers' brains learned to turn these vibrations into a mental picture of the room. Some became so good at it that they ducked when a ball was tossed at the camera.

What was regarded as fringe science 40 years ago is currently at the cutting edge of neuroscience. With the right training, scientists now know the brain can reshape itself to work around dead and damaged areas, often with dramatic benefits. Therapies that exploit the brain's power to adapt have helped people overcome damage caused by strokes, depression, anxiety and learning disabilities, and may one day replace drugs for some of these conditions. Some studies suggest therapies that tap into the brain's neuroplasticity are already making a big difference. Children with language difficulties have been shown to make significant progress using computer training tools that are the equivalent of cerebral cross-training. Work is underway to investigate whether it is possible to stave off a loss of brain plasticity in older age, which might help to address memory problems linked to Alzheimer's disease. Some psychoanalysts are adopting techniques to help people overcome relationship troubles, obsessions, worries and bad habits.

The idea of brain plasticity has been discovered and forgotten many times over the centuries. The ancient Greeks accepted the idea, with Socrates believing that people could train their brains the way gymnasts train their bodies. Around the time of Galileo, the idea fell out of favour, as scientists began to see the world mechanistically, with each object, organ and even parts of an organ being attributed well-defined, unchanging roles. It was these ideas that led to the notion of our brains being "hardwired", an idea that today is steadily being overturned.

Norman Doidge, a psychiatrist at the University of Toronto and author of the New York Times bestseller, The Brain That Changes Itself, says our ongoing belief that our brains are hardwired has held up medical progress. "Our best and brightest neuroscientists thought our brains were structured like complex machines, with each part performing one function in one location, and that had implications. If you were born with a part that was defective, and say it gave you a learning disorder, it meant there was nothing you could do, you had to learn to live with it. If you sustained a brain injury or had a stroke and part of your brain broke down, there was nothing you could do. Brain exercises made no sense, and even more fundamentally, human nature was as fixed as the brain from which it emerged," he says.

Neuroplasticity does not see the different regions of the brain as completely versatile and certainly not interchangeable. But it recognises that if part of the brain is damaged, it can be possible to train other areas to take on, at least to some extent, the job of the lost brain matter.

One of Doidge's case studies, Cheryl Schiltz, demonstrates how brain plasticity can transform a damaged life. Her story began in 1997, when, at the age of 39, she picked up an infection after a routine operation. To clear it up, she was given a course of the antibiotic, gentamicin. When used in excess, the drug can sometimes destroy cells in the inner ear, causing hearing loss, but it is cheap and effective, so is widely used. In Schiltz's case, gentamicin destroyed her vestibulary system, the looping canals of the inner ear that allow us to tell up from down. Tests showed she had only 2% of her vestibulary function left.

What happens to a person who cannot balance is striking. Schiltz felt as if she was constantly falling, and as a result, she usually did. When she hit the floor, the feeling didn't go away. Sometimes, it was as if a trapdoor had opened and she was free-falling into an abyss.

Her doctor found an ingenious way to treat her. He fitted her with a bizarre-looking helmet fitted with motion sensors. These fed signals to a metal strip that she placed in her mouth. Now, as she tipped forward, she felt a tingle ripple to the tip of her tongue. As her head moved to the side, the tingle rolled sideways.

The first time Schiltz put the device on she began to cry. The wobbles subsided. She felt safe. She could stand up. Over time, her brain learned to turn the feeling in her tongue into a sense of balance. After prolonged training sessions, Schiltz needed the helmet less and less. Her doctor thinks her brain tuned into the tiny signals coming from what remained of her vestibulary system, and recruited other brain nerves to help out.

There is a darker side to brain plasticity that Doidge has seen in some of his own patients. He has treated several men whose relationships were in tatters because of what Doidge calls an "epidemic" of internet porn addiction. The men had spent so much time viewing pornographic images, they had become impotent with their partners, and some developed extreme sexual tastes. Doidge believes that neuroplasticity was at work here, with the men's brains altered by an almost limitless supply of pictures, available any time at the click of a mouse. Most of the men recovered after being banned from using their computers and going cold turkey.

Some psychiatrists suspect that a common technique called cognitive behaviour therapy, which helps people to change their perspective on events in their lives, may work because of the brain's plasticity.

In his book, Doidge uses ideas of neuro-plasticity to promote ways of overcoming conditions such as obsessive-compulsive disorder, and other common problems, such as persistent worries and anxieties. In some instances, he suggests that people force themselves to do a rewarding task as soon as they get the urge to worry or check whether the stove is off for the seventh time. "You have a real civil war for four to six weeks, because your brain is pulling you one way and you are pushing in another, but when it works, it is very powerful," he says.

Doidge says he is not anti-medication, but wonders if therapies that tap into neuro-plasticity will soon replace drug treatments for certain conditions. "We can change our brains by sensing, imagining and acting in the world. It's economical and mostly low-tech, and I'm very, very hopeful".



The Brain That Changes Itself by Norman Doidge is published by Penguin.