The Brain That Changes Itself: Stories of Personal Triumph from the Frontiers of Brain Science

by Norman Doidge

The idea that the brain can change its own structure and function through thought and activity

some of our most stubborn habits and disorders are products of our plasticity. Once a particular plastic change occurs in the brain and becomes well established, it can prevent other changes from occurring.

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.

Merzenich argues that practicing a new skill, under the right conditions, can change hundreds of millions and possibly billions of the connections between the nerve cells in our brain maps.

When we say that neurons “rewire” themselves, we mean that alterations occur at the synapse, strengthening and increasing, or weakening and decreasing, the number of connections between the neurons.

When it came to allocating brain-processing power, brain maps were governed by competition for precious resources and the principle of use it or lose it.

If you ever ask yourself, “How often must I practice French, or guitar, or math to keep on top of it?” you are asking a question about competitive plasticity. You are asking how frequently you must practice one activity to make sure its brain map space is not lost to another.

the child goes from using a massive number of neurons to an appropriate few, well matched to the task. This more efficient use of neurons occurs whenever we become proficient at a skill, and it explains why we don’t quickly run out of map space as we practice or add skills to our repertoire.

lasting changes occurred only when his monkeys paid close attention. When the animals performed tasks automatically, without paying attention, they changed their brain maps, but the changes did not last. We often praise “the ability to multitask.” While you can learn when you divide your attention, divided attention doesn’t lead to abiding change in your brain maps.

Tallal’s research showed that children with language disabilities have auditory processing problems with common consonant-vowel combinations that are spoken quickly and are called “the fast parts of speech.”

Merzenich believed that these children’s auditory cortex neurons were firing too slowly,

Because they spent so much energy decoding words, they tended to use shorter sentences and failed to exercise their memory for longer sentences.

Scientific Learning, that is wholly devoted to using neuroplastic research to help people rewire their brains.

Fast ForWord is the name of the training program they developed for language-impaired and learning-disabled children.

The program exercises every basic brain function involved in language from decoding sounds up to comprehension—a kind of cerebral cross-training.

This “reward” is a crucial feature of the program, because each time the child is rewarded, his brain secretes such neurotransmitters as dopamine and acetylcholine, which help consolidate the map changes he has just made.

It is called a “pervasive developmental disorder,” because so many aspects of development are disturbed: intelligence, perception, socializing skills, language, and emotion.

Parents of autistic children who did Fast ForWord told Merzenich that their children became more connected socially.

the nucleus basalis helps us not only pay attention but remember what we are experiencing.

the nucleus can be activated only when something important, surprising, or novel occurs, or if we make the effort to pay close attention.

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.

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

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There are exercises for the frontal lobes that support our “executive functions” such as focusing on goals, extracting themes from what we perceive, and making decisions. These exercises are also designed to help people categorize things, follow complex instructions, and strengthen associative memory, which helps put people, places, and things into context.

Merzenich now believes there are times you want to shrink them. He has been working on developing a mental eraser that can eliminate a problematic brain map.

This technique could be of great use for people who have post-traumatic flashbacks, recurring obsessional thoughts, phobias, or problematic mental associations.

The brain structure that regulates instinctive behaviors, including sex, called the hypothalamus, is plastic, as is the amygdala, the structure that processes emotion and anxiety.

While some parts of the brain, such as the cortex, may have more plastic potential because there are more neurons and connections to be altered, even noncortical areas display plasticity.

actor Christopher Reeve, who suffered a severe spinal injury, demonstrated such plasticity, when he was able, through relentless exercise, to recover some feeling and mobility seven years after his accident.

A single dose of many addictive drugs will produce a protein, called ?FosB (pronounced “delta Fos B”), that accumulates in the neurons. Each time the drug is used, more ?FosB accumulates, until it throws a genetic switch, affecting which genes are turned on or off. Flipping this switch causes changes that persist long after the drug is stopped, leading to irreversible damage to the brain’s dopamine system and rendering the animal far more prone to addiction. Nondrug addictions, such as running and sucrose drinking, also lead to the accumulation of ?FosB and the same permanent changes in the dopamine system.

These “addictive symptoms”—the highs, crashes, cravings, withdrawal, and fixes—are subjective signs of plastic changes occurring in the structure of our brains, as they adapt to the presence or absence of the beloved.

Oxytocin’s “ability” to wipe out learned behavior has led some scientists to call it an amnestic hormone. Freeman proposes that oxytocin melts down existing neuronal connections that underlie existing attachments, so new attachments can be formed. Oxytocin, in this theory, does not teach parents to parent. Nor does it make lovers cooperative and kind; rather, it makes it possible for them to learn new patterns.

This relative lack of distress may also free us to learn new things and form new bonds, while partially reconfiguring our existing relationships.

The brain for Freeman is fundamentally an organ of socialization, and so there must be a mechanism that, from time to time, undoes our tendency to become overly individualized, overly self-involved, and too self-centered.

Fear can be exciting in frightening movies or on roller coasters. The human brain seems able to attach many of our feelings and sensations either to the pleasure system or to the pain system, and each of these links or mental associations requires a novel plastic connection in the brain.

What rewires patients’ brains is not mitts and slings, of course. Though they force the patients to practice using their damaged arms, the essence of the cure is the incremental training or shaping, increasing in difficulty over time. “Massed practice”—concentrating an extraordinary amount of exercise in only two weeks—helps rewire their brains by triggering plastic changes. Rewiring is not perfect after there has been massive brain death. New neurons have to take over the lost functions, and they may not be quite as effective as the ones they replace.

Based on his work with plasticity, Taub has discovered a number of training principles: training is more effective if the skill closely relates to everyday life; training should be done in increments; and work should be concentrated into a short time, a training technique Taub calls “massed practice,” which he has found far more effective than long-term but less frequent training.

Many of these same principles are used in “immersion” learning of a foreign language. How many of us have taken language courses over years and not learned as much as when we went to the country and “immersed” ourselves in the language for a far shorter period? Our time spent with people who don’t speak our native

tongue, forcing us to speak theirs, is the “constraint.” Daily immersion allows us to get “massed practice.” Our accent suggests to others that they may have to use simpler language with us; hence we are incrementally challenged, or shaped. Learned ...

After a brief period of practice, as when we cram for a test, it is relatively easy to improve because we are likely strengthening existing synaptic connections. But we quickly forget what we’ve crammed—because these are easy-come, easy-go neuronal connections and are rapidly reversed. Maintaining improvement and making a skill permanent require the slow steady work that probably forms new connections.

in some cases, the faster you can imagine something, the faster you can do it.

“The system is plastic, not elastic,” Pascual-Leone says in a booming voice. An elastic band can be stretched, but it always reverts to its former shape, and the molecules are not rearranged in the process. The plastic brain is perpetually altered by every encounter, every interaction.

An operator is a processor in the brain that, instead of processing input from a single sense, such as vision, touch, or hearing, processes more abstract information.

One operator processes information about spatial relationships, another movement, and another shapes. Spatial relationships, movement, and shapes are information that is processed by several of our senses.

for any brain activity, the ablest group of neurons is selected to do the task. There is an almost Darwinian competition—a neural Darwinism, to use Gerald Edelman’s phrase—going on all the time between operators to see which ones can most effectively process signals from a particular sense

Someone presented with an overwhelming auditory task, such as memorizing Homer’s Iliad, might blindfold himself to recruit operators usually devoted to sight, since the vast operators in the visual cortex can process sound.

a short-term memory becomes long-term when a chemical in the neuron, called protein kinase A, moves from the body of the neuron into its nucleus, where genes are stored. The protein turns on a gene to make a protein that alters the structure of the nerve ending, so that it grows new connections between the neurons.

Most people assume that our genes shape us—our behavior and our brain anatomy. Kandel’s work shows that when we learn our minds also affect which genes in our neurons are transcribed. Thus we can shape our genes, which in turn shape our brain’s microscopic anatomy.

Children who were molested when very young and unable to understand what was being done to them were not always upset at the time, and their initial memories were not always negative. But once they matured sexually, they looked upon the incident anew and gave it new meaning, and their memory of the molestation changed.