The Brain That Changes Itself (2007)
By Norman Doidge
Page 14 of 16
Merzenich has started a new company, Posit Science, devoted to helping people preserve the plasticity of their brains as they age and extend their mental lifespans. He’s sixty-one but is not reluctant about calling himself old. “I love old people. I’ve always loved old people. Probably my favorite person was my paternal grandfather, one of the three or four most intelligent and interesting people I’ve met in life.” Grandpa Merzenich came from Germany at nine on one of the last clipper ships. He was self-educated, an architect and a building contractor. He lived to be seventy-nine, at a time when life expectancy was closer to forty.
“It’s estimated that by the time someone who is sixty-five now dies, the life expectancy will be in the late eighties. Well, when you are eighty-five, there is a forty-seven percent chance that you will have Alzheimer’s disease.” He laughs. “So we’ve created this bizarre situation in which we are keeping people alive long enough so that on the average, half of them get the black rock before they die. We’ve got to do something about the mental lifespan, to extend it out and into the body’s lifespan.”
Merzenich thinks our neglect of intensive learning as we age leads the systems in the brain that modulate, regulate, and control plasticity to waste away. In response he has developed brain exercises for age-related cognitive decline—the common decline of memory, thinking, and processing speed.
Merzenich’s way of attacking mental decline is at odds with mainstream neuroscience. Tens of thousands of papers, written about the physical and chemical changes that occur in the aging brain, describe processes that occur as neurons die. There are many drugs on the market and scores of drugs in the pipeline designed to block these processes and raise levels of falling chemicals in the brain. Yet, Merzenich believes that such drugs, worth billions in sales, provide only about four to six months of improvement.
“And there is something really wrong about all this,” he says. “It all neglects the role of what is required to sustain normal skills and abilities...It is as if your skills and abilities, acquired in the brain at some young age, are just destined to deteriorate as the physical brain deteriorates.” The mainstream approach, he argues, is based on no real understanding of what it takes to develop a new skill in the brain, never mind to sustain it. “It is imagined,” he says, “that if you manipulate the levels of the right neurotransmitter...that memory will be recovered, and cognition will be useful, and that you will start moving like a gazelle again.”
The mainstream approach doesn’t take into account what is required to maintain a sharp memory. A major reason memory loss occurs as we age is that we have trouble registering new events in our nervous systems, because processing speed slows down, so that the accuracy, strength, and sharpness with which we perceive declines. If you can’t register something clearly, you won’t be able to remember it well.
Take one of the most common problems of aging, trouble finding words. Merzenich thinks this problem often occurs because of the gradual neglect and atrophy of the brain’s attentional system and nucleus basalis, which have to be engaged for plastic change to occur. This atrophy leads to our representing oral speech with “fuzzy engrams,” meaning that the representation of sounds or words is not sharp because the neurons that encode these fuzzy engrams are not firing in the coordinated, quick way needed to send a powerful sharp signal. Because the neurons that represent speech pass on fuzzy signals to all the neurons downstream from them (“muddy in, muddy out”) we also have trouble remembering, finding, and using words. It is similar to the problem we saw occurring in the brains of language-impaired children, who also have “noisy brains.”
When our brains are “noisy,” the signal for a new memory can’t compete against the background electrical activity of the brain, causing a “signal-noise problem.”
Merzenich says the system gets noisier for two reasons. First because as everyone knows, “everything is progressively going to hell.” But “the main reason it is getting noisier is that it is not being appropriately exercised.” The nucleus basalis, which works by secreting acetylcholine—which, as we said, helps the brain “tune in” and form sharp memories—has been totally neglected. In a person with mild cognitive impairment the acetylcholine produced in the nucleus basalis is not even measurable.
“We have an intense period of learning in childhood. Every day is a day of new stuff. And then, in our early employment, we are intensely engaged in learning and acquiring new skills and abilities. And more and more as we progress in life we are operating as users of mastered skills and abilities.”
Psychologically, middle age is often an appealing time because, all else being equal, it can be a relatively placid period compared with what has come before. Our bodies aren’t changing as they did in adolescence; we’re more likely to have a solid sense of who we are and be skilled at a career. We still regard ourselves as active, but we have a tendency to deceive ourselves into thinking that we are learning as we were before. We rarely engage in tasks in which we must focus our attention as closely as we did when we were younger, trying to learn a new vocabulary or master new skills. Such activities as reading the newspaper, practicing a profession of many years, and speaking our own language are mostly the replay of mastered skills, not learning. By the time we hit our seventies, we may not have systematically engaged the systems in the brain that regulate plasticity for fifty years.
That’s why learning a new language in old age is so good for improving and maintaining the memory generally. Because it requires intense focus, studying a new language turns on the control system for plasticity and keeps it in good shape for laying down sharp memories of all kinds. No doubt Fast ForWord is responsible for so many general improvements in thinking, in part because it stimulates the control system for plasticity to keep up its production of acetylcholine and dopamine. Anything that requires highly focused attention will help that system—learning new physical activities that require concentration, solving challenging puzzles, or making a career change that requires that you master new skills and material. Merzenich himself is an advocate of learning a new language in old age. “You will gradually sharpen everything up again, and that will be very highly beneficial to you.”
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