Adam Gazzaley in his laboratory in San Francisco, wearing an electroencephalogram cap, linked to an Oculus Rift. This allows a therapeutic VR game to respond in real time to brain activity, stimulating areas that need developing

Chris Crisman

One day in January 2007, a US federal government construction contractor called Doug Reitmeyer arrived at the offices of a brain-fitness software company called Posit Science, in downtown San Francisco. Reitmeyer's son, Ryan, had had a devastating boat accident two years earlier. At about 9.45pm, four of Ryan's friends had asked him to take them back to their car across the lake. Ryan, 29, was driving the small Sea Ray boat across lake Travis, a reservoir on the Colorado River in Texas, when it collided with a ten-metre black Carver cabin cruiser that had no lights on. The Sea Ray's five occupants went overboard and Ryan's head was crushed between the two boats. Surgery to remove the shattered bone that had pierced his brain lasted several hours and he was in a coma for two weeks. Surgeons had to remove part of his brain's frontal lobes, leaving him with an indentation in his head, where parts of his brain and skull were missing. When Doug Reitmeyer asked the surgeon if he could save his son's life, the surgeon said that he could, but that Ryan would probably never be able to speak or live independently again. Reitmeyer was willing to prove the medics wrong, so he took early retirement and dedicated his life to helping his son make a full recovery. He researched brain-damage therapies and attended conferences and seminars, until he came upon the work of Michael Merzenich, a neuroscientist at the University of California, San Francisco, and founder of Posit Science, a company pioneering brain-fitness software to improve memory and processing speed in older adults. Reitmeyer scheduled a meeting.

Merzenich has silver hair and exudes bonhomie. He talks with the confidence of someone who believes he's usually right. One of his mantras is to hear, feel and taste as if he were a child again. Every day he goes for walks and, comically, he varies his pace and the length of his stride, as a way of exercising his brain. He drives a Fiat 500 and refuses to use a GPS, or indeed any other technology that may act as a substitute for his brain. At the weekend he usually repairs to his villa in Santa Rosa, a 60-minute car journey north of San Francisco, where he tends to a small vegetable garden and vineyards. (His wife calls him "the farmer and the farmer's wife".) He is a member of the US National Academy of Sciences and, despite not being a medical doctor, is also a member of the Institute of Medicine, making him one of the few to have been elected to both academies.

Merzenich listened as Reitmeyer described the challenges facing his son Ryan, whose daily schedule at the time included sessions of neurofeedback, speech, physical and occupational therapies. Ryan had made some progress recovering his speech and movement but his memory and cognitive control remained deficient: Reitmeyer could take Ryan to a restaurant and his son would ask him when they were going to eat right after they'd had a meal. Merzenich reviewed Ryan's brain scans and medical records. Ryan was highly cognitively impaired, "down in the first few percentiles in cognitive ability". He had very restricted syntactic ability. He couldn't hold much of a conversation. He couldn't sustain attention and couldn't memorise something for more than a couple of minutes. Merzenich's software had been tested on patients with traumatic brain injury, but this case was so severe that Merzenich didn't even know if Ryan would be able to initiate the exercises. But when Reitmeyer asked Merzenich if he could help his son, the doctor said of course he could.

Merzenich tailored a programme of regimented brain-fitness training for Ryan. It was heavily focused on redeveloping language and auditory abilities, with further emphasis on other skills, such as cognitive control and visual-processing. Ryan had spent more than 50 hours completing Posit Science's brain-fitness exercises when he came to see Merzenich some months later.

"They came to thank us and to show how well Ryan was doing," Merzenich recalls. Ryan had recovered his memory and had made astonishing progress with his language and ability to control his attention. He could also hold a conversation and even use wit in his responses. Merzenich recalls Reitmeyer asking Ryan to pick something from a local drug store a couple of blocks away, a neighbourhood where Ryan had never been before. "And he did it. That would have been impossible a few months ago. They were so thankful. They knew that Ryan had come back into real life from such a deep hole," Merzenich says.

Merzenich keeps in touch with the Reitmeyers. Last time he spoke to Ryan, he was driving again, playing the guitar, had a job and was talking about getting married. "I choose not to talk about these things publicly, because I don't want people to think that if you have 30 per cent of your frontal lobes removed you can expect this kind of recovery," Merzenich says. "One thing is clear though. Ryan would have never have recovered from such an injury if the human brain didn't have a remarkable capacity to change."

Merzenich is one of the few scientists and doctors who, in the past 30 years, have transformed the field of neurology by overturning the dogma that our mental abilities are immutable and fixed early in life. Cognitive impairment associated with neurological maladies, such as schizophrenia, strokes, autism and traumatic brain injury, were considered largely untreatable. Normal age-related cognitive decline was considered unavoidable. The capacity to train and improve the diverse mental abilities that make up our intelligence was not considered possible. But Merzenich and other researchers have shown that the brain is what they call "plastic" -- it can physically remodel itself. The notion that the brain we are born with is not a fixed structure with a set of weaknesses and strengths, but a mutable organ that is adaptable and can be trained to overcome its deficiencies, has profound implications for how we perceive our brain and its associated capacities. Not only can brain plasticity be manipulated in ways that treat and prevent neuronal disease that was deemed permanent, but it can also keep our brains fit and resilient. "It means you're not stuck with it," Merzenich says. "We can improve and often fix it, whether you're 90 or when you're nine."

In 1968, Merzenich made his first breakthrough. He was a recent neuroscience graduate, studying at the University of Wisconsin-Madison under the supervision of a neurophysiologist called Clinton Woolsey. Merzenich was an expert in a technique called "micromapping", a precise but time-consuming way of finding which parts of the brain responded to external stimuli, using extremely small electrodes that measure the electrical activity of a single neuron. Merzenich used macaque monkeys, measuring neuronal activity as he tapped different parts of the monkey's hand, in order to see which areas of it stimulated electrical activity in the monitored part of the brain. Mapping a whole hand using this method could take between 20 and 40 hours.

When he arrived at Madison, Woolsey asked Merzenich to supervise two young neurosurgeons, Ron Paul and Herbert Goodman, and the three set out to find what happened in the brain of adult macaque monkeys after a severe hand injury. The mainstream view at the time was that the brain reached a fixed state after just one year of existence. If, for instance, one of the main nerves in the hand were cut, then the corresponding area in the brain was supposed to be rendered silent and unused from the lack of sensorial input. Merzenich, Paul and Goodman, however, found that this wasn't the case. After the injury, neighbouring areas in the brain would expand into the vacant territory. Later, as the nerve regenerated, its corresponding brain connections would reclaim much of its original neurological real estate. This dynamic remodelling of the brain that Merzenich and his colleagues observed was completely at odds with the conventional view that the structure of a brain was immutable. In their scientific report, they wrote a lengthy discussion section about what these observations implied. Woolsey thought it was too conjectural and deleted it.

Michael Merzenich, cofounder and CSO of Posit Science, a San Francisco-based firm that creates brain-training and rehabilitation software

Chris Crisman

When, in 1971, Merzenich moved to the University of California, San Francisco, he continued his experiments at the department of otolaryngology, and showed again and again that adult brains remained plastic. The scientific establishment, however, was slow to accept it. Early reviews of his scientific papers often came back with sarcastic comments, and at conferences he was subjected to insults. That didn't bother him. He was sure that the scientific truth always wins in the end.

"What irritated me is that I was also arguing that this discovery could be used for all sorts of therapies," Merzenich says. "I became a sort of missionary going to people and saying, 'Listen, you should take this research seriously, it can help people.'" It took a couple of decades. In the late 80s, he met a neuroscientist from Rutgers University in New Jersey, called Paula Tallal. Tallal was interested in children who had difficulties reading and speaking, such as dyslexics. Her studies showed that children with dyslexia had something wrong with their brains. At the time, scientists believed that dyslexics had a deficiency with their eyes, but Tallal suspected that instead their brains were too slow in processing sound. "People thought dyslexia had something to do with seeing letters backwards," says Tallal. "However, words are made of smaller units of sound represented by letters. It was becoming clear that the majority of dyslexic children find it difficult to be aware that words can be broken down into sounds. This in turn will affect their reading ability, because reading stands on the shoulders of spoken language. And because learning to read requires matching symbols to sounds, the child will be affected in understanding words and speech."

At the time, Merzenich had been conducting experiments with adult macaque monkeys that showed how radically their brains rewired after they learned new skills, such as being able to distinguish sounds in shorter and shorter periods of time. "We would progressively train them to an extent that their initially sluggish brains were fast and accurate," Merzenich says. When Tallal told him about her findings, Merzenich wondered if he could train these kids who lacked the necessary neurological circuitry to process sounds at speed. "Paula, if these kids were monkeys, I'm almost certain I could fix them," he told her.

Tallal and Merzenich decided to collaborate. In six months, with the help of a team of language specialists, neuroscientists and computer scientists, they developed language-training software called Fast ForWord. Fast ForWord consisted of games that used acoustically enhanced speech, which initially made very rapid acoustic changes longer and louder and then would slowly revert back into a normal speech range. For a month during the summer of 1994, seven dyslexic children came to Tallal's lab in Newark, New Jersey, to exercise their brains with the software. "At the time, the software was still very limited," Merzenich says. "The difference it made on the children, however, was amazing."

He remembers a quiet five-year-old boy who had the language abilities of a 30-month-old. "He was very limited, but when we returned to Newark after the tests he was a confident chatterbox. His tests indicated that his language ability was now normal after a month," Merzenich says.

Tallal and Merzenich decided to conduct a larger-scale controlled trial with improved software and more children, the results of which were later published in the journal Science. Within days of the report coming out, Merzenich and Tallal received thousands of messages from parents and therapists desperate to try the new treatment on their children. In 1996, Tallal and Merzenich, along with two other neuroscientists, founded the Scientific Learning Corporation, a company that produces Fast ForWord today. It was the first company to provide a brain-fitness programme online. To date, according to Tallal, Fast ForWord has helped more than two million children overcome learning disabilities.

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