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

by Norman Doidge

One of these scientists even showed that thinking, learning, and acting can turn our genes on or off, thus shaping our brain anatomy and our behavior—surely one of the most extraordinary discoveries of the twentieth century.

Language development, for instance, has a critical period that begins in infancy and ends between eight years and puberty. After this critical period closes, a person’s ability to learn a second language without an accent is limited. In fact, second languages learned after the critical period are not processed in the same part of the brain as is the native tongue.

Each neuron has three parts. The dendrites are treelike branches that receive input from other neurons. These dendrites lead into the cell body, which sustains the life of the cell and contains its DNA. Finally the axon is a living cable of varying lengths (from microscopic lengths in the brain, to some that can run down to the legs and reach up to six feet long). Axons are often compared to wires because they carry electrical impulses at very high speeds (from 2 to 200 miles per hour) toward the dendrites of neighboring neurons.

Axons don’t quite touch the neighboring dendrites. They are separated by a microscopic space called a synapse. Once an electrical signal gets to the end of the axon, it triggers the release of a chemical messenger, called a neurotransmitter, into the synapse. The chemical messenger floats over to the dendrite of the adjacent neuron, exciting or inhibiting it. When we say that neurons “rewire” themselves, we mean that alterations occur at the synapse,

The experiment demonstrated that if the median nerve was cut, other nerves, still brimming with electrical input, would take over the unused map space to process their input. 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.

While you can learn when you divide your attention, divided attention doesn’t lead to abiding change in your brain maps.

Merzenich continues to challenge the view that we are stuck with the brain we have at birth. The Merzenich brain is structured by its constant collaboration with the world, and it is not only the parts of the brain most exposed to the world, such as our senses, that are shaped by experience. Plastic change, caused by our experience, travels deep into the brain and ultimately even into our genes, molding them as well

Dopamine, as we saw in Merzenich’s work, is also involved in plastic change. The same surge of dopamine that thrills us also consolidates the neuronal connections responsible for the behaviors that led us to accomplish our goal.

Eric Nestler, at the University of Texas, has shown how addictions cause permanent changes in the brains of animals. A single dose of many addictive drugs will produce a protein, called ΔFosB (pronounced “delta Fos B”), that accumulates in the neurons. Each time the drug is used, more ΔFosB 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 ΔFosB and the same permanent changes in the dopamine system.

A drug like cocaine acts on us by lowering the threshold at which our pleasure centers will fire, making it easier for them to turn on.

When we learn something new, neurons fire together and wire together, and a chemical process occurs at the neuronal level called “long-term potentiation,” or LTP, which strengthens the connections between the neurons. When the brain unlearns associations and disconnects neurons, another chemical process occurs, called “long-term depression,” or LTD (which has nothing to do with a depressed mood state). Unlearning and weakening connections between neurons is just as plastic a process, and just as important, as learning and strengthening them.

Often such people cannot move on because they cannot yet grieve; the thought of living without the one they love is too painful to bear. In neuroplastic terms, if the romantic or the widow is to begin a new relationship without baggage, each must first rewire billions of connections in their brains. The work of mourning is piecemeal,

Neuromodulators are different from neurotransmitters. While neurotransmitters are released in the synapses to excite or inhibit neurons, neuromodulators enhance or diminish the overall effectiveness of the synaptic connections and bring about enduring change. Freeman believes that when we commit in love, the brain neuromodulator oxytocin is released, allowing existing neuronal connections to melt away so that changes on a large scale can follow.

Then Taub had another epiphany, the one that would transform the treatment of strokes. He proposed that the reason a monkey didn’t use its arm after a single limb was deafferented was because it had learned not to use it in the period right after the operation when the spinal cord was still in “spinal shock” from the surgery. Spinal shock can last from two to six months, a period when the neurons have difficulty firing. An animal in spinal shock will try to move its affected arm and fail many times during those months. Without positive reinforcement, the animal gives up and instead uses its good arm to feed itself, getting positive reinforcement each time it succeeds. And thus the motor map for the deafferented arm—which includes programs for common arm movements—begins to weaken and atrophy, according to the plasticity principle of use it or lose it.

training should be done in increments; and work should be concentrated into a short time, a training technique Taub calls “massed practice,”

when a brain map is not used, the brain can reorganize itself so that another mental function takes over that processing space.

We now know, from brain scans, that three parts of the brain are involved in obsessions. We detect mistakes with our orbital frontal cortex, part of the frontal lobe, on the underside of the brain, just behind our eyes. Scans show that the more obsessive a person is, the more activated the orbital frontal cortex is. Once the orbital frontal cortex has fired the “mistake feeling” it sends a signal to the cingulate gyrus, located in the deepest part of the cortex. The cingulate triggers the dreadful anxiety that something bad is going to happen unless we correct the mistake and sends signals to both the gut and the heart, causing the physical sensations we associate with dread. The “automatic gearshift,” the caudate nucleus, sits deep in the center of the brain and allows our thoughts to flow from one to the next unless, as happens in OCD, the caudate becomes extremely “sticky.”

Schwartz set out to develop a treatment that would change the OCD circuit by unlocking the link between the orbital cortex and the cingulate and normalizing the functioning of the caudate. Schwartz wondered whether patients could shift the caudate “manually” by paying constant, effortful attention and actively focusing on something besides the worry, such as a new, pleasurable activity. This approach makes plastic sense because it “grows” a new brain circuit that gives pleasure and triggers dopamine release which, as we have seen, rewards the new activity and consolidates and grows new neuronal connections. This new circuit can eventually compete with the older one, and according to use it or lose it, the pathological networks will weaken. With this treatment we don’t so much “break” bad habits as replace bad behaviors with better ones.

When Ramachandran reviewed the histories of people with painful frozen arms, he discovered that they had all had their arms in slings or casts for several months before amputation. Their brain maps now seemed to record, for all time, the fixed position of the arm just prior to amputation. He began to suspect that it was the very fact that the limb did not exist that allowed the sensation of paralysis to persist. Normally, when the motor command center in the brain sends out an order to move the arm, the brain gets feedback from various senses, confirming that the order has been executed. But the brain of a person without a limb never gets confirmation that the arm has moved, since there are neither arm nor motion sensors in the arm to provide that feedback. Thus, the brain is left with the impression that the arm is frozen. Because the arm had been stuck in a cast or sling for months, the brain map developed a representation of the arm as unmoving. When the arm was removed, there was no new input to alter the brain map, so the mental representation of the limb as fixed became frozen in time—a situation similar to the learned paralysis that Taub discovered in stroke patients.

Their “gate control theory of pain” proposed a series of controls, or “gates,” between the site of injury and the brain. When pain messages are sent from damaged tissue through the nervous system, they pass through several “gates,” starting in the spinal cord, before they get to the brain. But these messages travel only if the brain gives them “permission,” after determining they are important enough to be let through. If permission is granted, a gate will open and increase the feeling of pain by allowing certain neurons to turn on and transmit their signals. The brain can also close a gate and block the pain signal by releasing endorphins, the narcotics made by the body to quell pain.

The gate theory also made Western scientists less skeptical of acupuncture, which reduces pain by stimulating points of the body often far from the site where the pain is felt. It seemed possible that acupuncture turns on neurons that inhibit pain, closing gates and blocking pain perception.

“Pain is an opinion on the organism’s state of health rather than a mere reflexive response to injury.

our thoughts can change the material structure of our brains.

Clearly mental practice is an effective way to prepare for learning a physical skill with minimal physical practice.

people like Gamm rely on long-term memory to help them solve mathematical problems when others rely on short-term memory. Experts don’t store the answers, but they do store key facts and strategies that help them get answers, and they have immediate access to them, as though they were in short-term memory. This use of long-term memory for problem solving is typical of experts in most fields, and Ericsson found that becoming an expert in most fields usually takes about a decade of concentrated effort.

The human brain can reorganize so quickly because individual parts of the brain are not necessarily committed to processing particular senses. We can, and routinely do, use parts of our brains for many different tasks.

Everything your “immaterial” mind imagines leaves material traces. Each thought alters the physical state of your brain synapses at a microscopic level. Each time you imagine moving your fingers across the keys to play the piano, you alter the tendrils in your living brain.

Our genes have two functions. The first, the “template function,” allows our genes to replicate, making copies of themselves that are passed from generation to generation. The template function is beyond our control. The second is the “transcription function.” Each cell in our body contains all our genes, but not all those genes are turned on, or expressed. When a gene is turned on, it makes a new protein that alters the structure and function of the cell. This is called the transcription function because when the gene is turned on, information about how to make these proteins is “transcribed” or read from the individual gene. This transcription function is influenced by what we do and think.

The first plastic concept Freud developed is the law that neurons that fire together wire together, usually called Hebb’s law, though Freud proposed it in 1888, sixty years before Hebb.

Freud’s second plastic idea was that of the psychological critical period and the related idea of sexual plasticity. As we saw in chapter 4, “Acquiring Tastes and Loves,” Freud was the first to argue that human sexuality and the ability to love have critical periods in early childhood that he called “phases of organization.” What happens during these critical periods has an inordinate effect on our ability to love and relate later in life. If something goes awry, it is possible to make changes later in life, but plastic change is much harder to achieve after a critical period closes.

Freud’s third idea was a plastic view of memory. The idea Freud inherited from his teachers was that events we experience can leave permanent memory traces in our minds.

In 1896 Freud wrote that from time to time memory traces are subjected to “a rearrangement in accordance with fresh circumstances—to a retranscription.

certain traumatic memories of events that happened early in childhood are not easily accessible to consciousness, so they don’t change.

Freud’s fourth neuroplastic idea helped explain how it might be possible to make unconscious traumatic memories conscious and retranscribe them. He observed that in the mild sensory deprivation created by his sitting out of the patients’ view, and commenting only when he had insights into their problems, patients began to regard him as they had important people in their past, usually their parents, especially in their critical psychological periods. It was as though the patients were reliving past memories without being aware of it. Freud called this unconscious phenomenon “transference” because patients were transferring scenes and ways of perceiving from the past onto the present.

The right hemisphere generally processes nonverbal communication; it allows us to recognize faces and read facial expressions, and it connects us to other people. It thus processes the nonverbal visual cues exchanged between a mother and her baby. It also processes the musical component of speech, or tone, by which we convey emotion. During the right hemisphere’s growth spurt, from birth until the second year, these functions undergo critical periods. The left hemisphere generally processes the verbal-linguistic elements of speech, as opposed to the emotional-musical ones, and analyzes problems using conscious processing. Babies have a larger right hemisphere, up to the end of the second year, and because the left hemisphere is only beginning its growth spurt, our right hemisphere dominates the brain for the first three years of our lives.

Antidepressant medications increase the number of stem cells that become new neurons in the hippocampus.

He is social, but not in large groups. “I don’t go readily to cocktail parties, where people just come together and talk. I don’t tend to like that kind of thing. I’d rather sit down with somebody and find a mutual topic of interest, and explore it in depth with that person, or maybe two or three people. Not a conversation that says how do you feel.”

From his research Grafman has identified four kinds of plasticity. The first is “map expansion,” described above, which occurs largely at the boundaries between brain areas as a result of daily activity.

The second is “sensory reassignment,” which occurs when one sense is blocked, as in the blind. When the visual cortex is deprived of its normal inputs, it can receive new inputs from another sense, such as touch.

The third is “compensatory masquerade,” which takes advantage of the fact that there’s more than one way for your brain to approach a task. Some people use visual landmarks to get from place to place. Others with “a good sense of direction” have a strong spatial sense, so if they lose their spatial sense in a brain injury, they can fall back on landmarks. Until neuroplasticity was recognized, compensatory masquerade—also called compensation or “alternative strategies” such as ...

The fourth kind of plasticity is “mirror region takeover.” When part of one hemisphere fails, the mirror region in the opposite hemisphere adapts, takin...

These experiments and many others like them confirm that Easterners perceive holistically, viewing objects as they are related to each other or in a context, whereas Westerners perceive them in isolation. Easterners see through a wide-angle lens; Westerners use a narrow one with a sharper focus.