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January 21 - February 8, 2022
They showed that the brain changed its very structure with each different activity it performed, perfecting its circuits so it was better suited to the task at hand. If certain “parts” failed, then other parts could sometimes take over. The machine metaphor, of the brain as an organ with specialized parts, could not fully account for changes the scientists were seeing. They began to call this fundamental brain property “neuroplasticity.”
The semicircular canals contain little hairs in a fluid bath. When we move our head, the fluid stirs the hairs, which send a signal to our brains telling us that we have increased our velocity in a particular direction.
Old people are more frightened of falling than of being mugged. A third of the elderly fall, and because they fear falling, they stay home, don’t use their limbs, and become more physically frail.
A brain system is made of many neuronal pathways, or neurons that are connected to one another and working together. If certain key pathways are blocked, then the brain uses older pathways to go around them.
These “secondary” neural pathways are “unmasked,” or exposed, and, with use, strengthened. This “unmasking” is generally thought to be one of the main ways the plastic brain reorganizes itself.
When she finally started to get the answers, she added hands for seconds and sixtieths of a second. At the end of many exhausting weeks, not only could she read clocks faster than normal people, but she noticed improvements in her other difficulties relating to symbols and began for the first time to grasp grammar, math, and logic. Most important, she could understand what people were saying as they said it. For the first time in her life, she began to live in real time.
It is far better to nip brain problems in the bud than to allow the child to wire into his brain the idea that he is “stupid,” begin to hate school and learning, and stop work in the weakened area, losing whatever strength he may have.
Over the years his labs and others have shown that stimulating the brain makes it grow in almost every conceivable way.
For people, postmortem examinations have shown that education increases the number of branches among neurons. An increased number of branches drives the neurons farther apart, leading to an increase in the volume and thickness of the brain. The idea that the brain is like a muscle that grows with exercise is not just a metaphor.
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.
He also discovered that when he touched certain parts of the brain, he triggered long-lost childhood memories or dreamlike scenes—which implied that higher mental activities were also mapped in the brain.
They also discovered that there was a “critical period,” from the third to the eighth week of life, when the newborn kitten’s brain had to receive visual stimulation in order to develop normally. In the crucial experiment Hubel and Wiesel sewed shut one eyelid of a kitten during its critical period, so the eye got no visual stimulation. When they opened this shut eye, they found that the visual areas in the brain map that normally processed input from the shut eye had failed to develop, leaving the kitten blind in that eye for life.
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.
The competitive nature of plasticity affects us all. There is an endless war of nerves going on inside each of our brains. If we stop exercising our mental skills, we do not just forget them: the brain map space for those skills is turned over to the skills we practice instead. 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.
Competitive plasticity also explains why our bad habits are so difficult to break or “unlearn.” Most of us think of the brain as a container and learning as putting something in it. When we try to break a bad habit, we think the solution is to put something new into the container. But when we learn a bad habit, it takes over a brain map, and each time we repeat it, it claims more control of that map and prevents the use of that space for “good” habits. That is why “unlearning” is often a lot harder than learning, and why early childhood education is so important—it’s best to get it right
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In 1949 Hebb proposed that learning linked neurons in new ways. He proposed that when two neurons fire at the same time repeatedly (or when one fires, causing another to fire), chemical changes occur in both, so that the two tend to connect more strongly. Hebb’s concept—actually proposed by Freud sixty years before—was neatly summarized by neuroscientist Carla Shatz: Neurons that fire together wire together.
Neurons that fire apart wire apart—or Neurons out of sync fail to link.
Topographical organization is efficient, because it means that parts of the brain that often work together are close together in the brain map, so signals don’t have to travel far in the brain itself.
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.
Faster neurons ultimately lead to faster thought—no minor matter—because speed of thought is a crucial component of intelligence. IQ tests, like life, measure not only whether you can get the right answer but how long it takes you to get it. They also discovered that as they trained an animal at a skill, not only did its neurons fire faster, but because they were faster their signals were clearer. Faster neurons were more likely to fire in sync with each other—becoming better team players—wiring together more and forming groups of neurons that gave off clearer and more powerful signals.
Finally, Merzenich discovered that paying close attention is essential to long-term plastic change. In numerous experiments he found that 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.
Whenever a goal is achieved, something funny happens: the character in the animation eats the answer, gets indigestion, gets a funny look on its face, or makes some slapstick move that is unexpected enough to keep the child attentive. 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. (Dopamine reinforces the reward, and acetylcholine helps the brain “tune in” and sharpen memories.)
staggering rate that can’t be explained by genetics alone. When the condition was first recognized over forty years ago, about one in 5,000 people had it. Now Merzenich believes it is at least fifteen in 5000.
After the critical period older children and adults can, of course, learn languages, but they really have to work to pay attention. For Merzenich, the difference between critical-period plasticity and adult plasticity is that in the critical period the brain maps can be changed just by being exposed to the world because “the learning machinery is continuously on.”
Several studies alerted him to how an environmental factor might contribute. One disturbing study showed that the closer children lived to the noisy airport in Frankfurt, Germany, the lower their intelligence was. A similar study, on children in public housing high-rises above the Dan Ryan Expressway in Chicago, found that the closer their floor was to the highway, the lower their intelligence.
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.
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.”
“Everything that you can see happen in a young brain can happen in an older brain.” The only requirement is that the person must have enough of a reward, or punishment, to keep paying attention through what might otherwise be a boring training session. If so, he says, “the changes can be every bit as great as the changes in a newborn.”
Freud discovered that the sexual abuse of children is harmful because it influences the critical period of sexuality in childhood, shaping our later attractions and thoughts about sex. Children are needy and typically develop passionate attachments to their parents. If the parent is warm, gentle, and reliable, the child will frequently develop a taste for that kind of relationship later on; if the parent is disengaged, cool, distant, self-involved, angry, ambivalent, or erratic, the child may seek out an adult mate who has similar tendencies.
An MSNBC.com survey of viewers in 2001 found that 80 percent felt they were spending so much time on pornographic sites that they were putting their relationships or jobs at risk.
They reported increasing difficulty in being turned on by their actual sexual partners, spouses or girlfriends, though they still considered them objectively attractive. When I asked if this phenomenon had any relationship to viewing pornography, they answered that it initially helped them get more excited during sex but over time had the opposite effect.
He recognizes that he is like a drug addict who can no longer get high on the images that once turned him on. And the danger is that this tolerance will carry over into relationships, as it did in patients whom I was seeing, leading to potency problems and new, at times unwelcome, tastes. When pornographers boast that they are pushing the envelope by introducing new, harder themes, what they don’t say is that they must, because their customers are building up a tolerance to the content. The back pages of men’s risqué magazines and Internet porn sites are filled with ads for Viagra-type drugs
All addicts show a loss of control of the activity, compulsively seek it out despite negative consequences, develop tolerance so that they need higher and higher levels of stimulation for satisfaction, and experience withdrawal if they can’t consummate the addictive act.
Pornography is more exciting than satisfying because we have two separate pleasure systems in our brains, one that has to do with exciting pleasure and one with satisfying pleasure.
Porn sites generate catalogs of common kinks and mix them together in images. Sooner or later the surfer finds a killer combination that presses a number of his sexual buttons at once. Then he reinforces the network by viewing the images repeatedly, masturbating, releasing dopamine and strengthening these networks. He has created a kind of “neosexuality,” a rebuilt libido that has strong roots in his buried sexual tendencies.
Stendhal, the nineteenth-century novelist and essayist, understood that love could lead to radical changes in attraction. Romantic love triggers such powerful emotion that we can reconfigure what we find attractive, even overcoming “objective” beauty.
When the pleasure centers are turned on, everything we experience gives us pleasure. 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. It is not simply the cocaine that gives us pleasure. It is the fact that our pleasure centers now fire so easily that makes whatever we experience feel great. It is not just cocaine that can lower the threshold at which our pleasure centers fire. When people with bipolar disorder (formerly called manic depression) begin to move toward their manic highs, their pleasure centers
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Because the pleasure centers are firing so freely, the enamored person falls in love not only with the beloved but with the world and romanticizes his view of it.
Globalization not only allows us to take more pleasure in the world, it also makes it harder for us to experience pain and displeasure or aversion.
But the pains of love also have a chemistry. When separated for too long, lovers crash and experience withdrawal, crave their beloved, get anxious, doubt themselves, lose their energy, and feel run-down if not depressed.
Different chemistries are involved in learning than in unlearning. 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
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Oxytocin is sometimes called the commitment neuromodulator because it reinforces bonding in mammals. It is released when lovers connect and make love—in humans oxytocin is released in both sexes during orgasm—and when couples parent and nurture their children. In women oxytocin is released during labor and breast-feeding. An fMRI study shows that when mothers look at photos of their children, brain regions rich in oxytocin are activated.
Oxytocin appears also to attach children to parents, and the neurons that control its secretion may have a critical period of their own. Children reared in orphanages without close loving contact often have bonding problems when older. Their oxytocin levels remain low for several years after they have been adopted by loving families.
Whereas dopamine induces excitement, puts us into high gear, and triggers sexual arousal, oxytocin induces a calm, warm mood that increases tender feelings and attachment and may lead us to lower our guard. A recent study shows that oxytocin also triggers trust.
With obsessions and compulsions, the more you do it, the more you want to do it; the less you do it, the less you want to do it. Schwartz has found it essential to understand that it is not what you feel while applying the technique that counts, it is what you do. “The struggle is not to make the feeling go away; the struggle is not to give in to the feeling”—by acting out a compulsion, or thinking about the obsession. This technique won’t give immediate relief because lasting neuroplastic change takes time, but it does lay the groundwork for change by exercising the brain in a new way.
Wall and Melzack’s theory asserted that the pain system is spread throughout the brain and spinal cord, and far from being a passive recipient of pain, the brain always controls the pain signals we feel.
How much pain we feel is determined in significant part by our brains and minds—our current mood, our past experiences of pain, our psychology, and how serious we think our injury is.
he found that the maps for people’s “Braille reading fingers” were larger than the maps for their other index fingers and also those for the index fingers of non-Braille readers. Pascual-Leone also found that the motor maps increased in size as the subjects increased the number of words per minute they could read.
some people, the “tortoises,” who seem slow to pick up a skill, may nevertheless learn it better than their “hare” friends—the “quick studies” who won’t necessarily hold on to what they have learned without the sustained practice that solidifies the learning.
Pascual-Leone found that both groups learned to play the sequence, and both showed similar brain map changes. Remarkably, mental practice alone produced the same physical changes in the motor system as actually playing the piece.
