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December 26, 2019 - January 2, 2020
It has recently been discovered that early childhood trauma causes massive plastic change in the hippocampus, shrinking it so that new, long-term explicit memories cannot form.
a downside of the plastic brain: we literally lose essential cortical real estate in response to illness. If the stress is brief, this decrease in size is temporary. If it is too prolonged, the damage is permanent.
The plastic paradox is that the same neuroplastic properties that allow us to change our brains and produce more flexible behaviors can also allow us to produce more rigid ones.
the absence of plasticity seemed related to force of habit.
Psychoanalysis is often about turning our ghosts into ancestors, even for patients who have not lost loved ones to death. We are often haunted by important relationships from the past that influence us unconsciously in the present.
we can transform implicit memories—which we are often not aware exist until they are evoked and thus seem to come at us “out of the blue”—into declarative memories that now have a clear context, which makes them easier to recollect and experience as part of the past.
He is always looking for novel things to do, and once he’s engaged in something, he turns his full attention to it—the necessary condition for plastic change.
neuronal stem cells in other parts of the human brain. So far they’ve also been found active in the olfactory bulb (a processing area for smell) and dormant and inactive in the septum (which processes emotion), the striatum (which processes movement), and the spinal cord.
This theory, that novel environments may trigger neurogenesis, is consistent with Merzenich’s discovery that in order to keep the brain fit, we must learn something new, rather than simply replaying already-mastered skills.
physical exercise and learning work in complementary ways: the first to make new stem cells, the second to prolong their survival.
Recent research shows that exercise stimulates the production and release of the neuronal growth factor BDNF, which, as we saw in chapter 3, “Redesigning the Brain,” plays a crucial role in effecting plastic change.
whatever keeps the heart and blood vessels fit invigorates the brain, including a healthy diet.
simply walking, at a good pace, stimulates the growth of new neurons.
Nothing speeds brain atrophy more than being immobilized in the same environment; the monotony undermines our dopamine and attentional systems crucial to maintaining brain plasticity.
We might think, “What for? Who am I fooling? I’m at the end of the road.” But that thinking is a self-fulfilling prophecy, which hastens the mental decline of the use-it-or-lose-it brain.
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the frontal lobes, which coordinate other parts of the brain and help the mind focus on the main point of a situation, form goals, and make lasting decisions.
Grafman’s data suggested that highly intelligent soldiers seemed better able to reorganize their cognitive abilities to support the areas that had been injured.
The brain is divided into sectors, and in the course of development each acquires a primary responsibility for a particular kind of mental activity.
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.
The fourth kind of plasticity is “mirror region takeover.” When part of one hemisphere fails, the mirror region in the opposite hemisphere adapts, taking over its mental function as best it can.
People with right-prefrontal lesions have impaired foresight.
the two hemispheres are in constant communication. Each not only informs the other of its own activities but also corrects its mate, at times restraining it and balancing the other’s eccentricities.
Betty Edwards’s popular book Drawing on the Right Side of the Brain, written in 1979, years before Miller’s discovery, taught people to draw by developing ways to stop the verbal, analytical left hemisphere from inhibiting the right hemisphere’s artistic tendencies.
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“Our brains are vastly different, in fine detail, from the brains of our ancestors…In each stage of cultural development…the average human had to learn complex new skills and abilities that all involve massive brain change…Each one of us can actually learn an incredibly elaborate set of ancestrally developed skills and abilities in our lifetimes, in a sense generating a re-creation of this history of cultural evolution via brain plasticity.”
culture and the brain implies a two-way street: the brain and genetics produce culture, but culture also shapes the brain. Sometimes these changes can be dramatic.
An fMRI study shows that we recognize cars and trucks with the same brain module we use to recognize faces.
in the plastic brain, change in one area or brain function “flows” through the brain, typically altering the modules that are connected to it.
Merzenich and Pascual-Leone argued that a fundamental rule of brain plasticity is that when two areas begin to interact, they influence each other and form a new whole.
The dichotomy between “low” instinctual and “high” cerebral begins to disappear. Whenever the low and the high transform each other to create a new whole, we can call it a sublimation.
Immigration is hard on the plastic brain. The process of learning a culture—acculturation—is an “additive” experience, of learning new things and making new neuronal connections as we “acquire” culture.
Additive plasticity occurs when brain change involves growth. But plasticity is also “subtractive” and can involve “taking things away,”
Each time the plastic brain acquires culture and uses it repeatedly, there is an opportunity cost: the brain loses some neural structure in the process, because plasticity is competitive.
Immigration is usually an unending, brutal workout for the adult brain, requiring a massive rewiring of vast amounts of our cortical real estate. It is a far more difficult matter than simply learning new things, because the new culture is in plastic competition with neural networks that had their critical period of development in the native land.
Successful assimilation, with few exceptions, requires at least a generation.
“Perceptual learning” is the kind of learning that occurs whenever the brain learns how to perceive with more acuteness
Perceptual learning is also involved in the plasticity-based structural change that occurs when Merzenich’s Fast ForWord helps children with auditory discrimination problems develop more refined brain maps, so they can hear normal speech for the first time.
To a larger degree than we suspected, culture determines what we can and cannot perceive.
Westerners approach the world “analytically,” dividing what they observe into individual parts. Easterners tend to approach the world more “holistically,” perceiving by looking at “the whole,” and emphasizing the interrelatedness of all things.
Bruce Wexler, a psychiatrist and researcher from Yale University, argues, in his book Brain and Culture,
Increasingly, the aging individual acts to preserve the structures within, and when there is a mismatch between his internal neurocognitive structures and the world, he seeks to change the world. In small ways he begins to micromanage his environment, to control it and make it familiar.
Television watching, one of the signature activities of our culture, correlates with brain problems. A recent study of more than twenty-six hundred toddlers shows that early exposure to television between the ages of one and three correlates with problems paying attention and controlling impulses later in childhood.
For every hour of TV the toddlers watched each day, their chances of developing serious attentional difficulties at age seven increased by 10 percent.
the media change our brains irrespective of content, and he famously said, “The medium is the message.” McLuhan was arguing that each medium reorganizes our mind and brain in its own unique way and that the consequences of these reorganizations are far more significant than the effects of the content or “message.”
Video games, like Internet porn, meet all the conditions for plastic brain map changes.
dopamine—the reward neurotransmitter, also triggered by addictive drugs—is released in the brain during these games. People who are addicted to computer games show all the signs of other addictions: cravings when they stop, neglect of other activities, euphoria when on the computer, and a tendency to deny or minimize their actual involvement.
It is the form of the television medium—cuts, edits, zooms, pans, and sudden noises—that alters the brain, by activating what Pavlov called the “orienting response,” which occurs whenever we sense a sudden change in the world around us, especially a sudden movement.
What we have learned by looking closely at neuroplasticity and the plastic paradox is that human neuroplasticity contributes to both the constrained and the unconstrained aspects of our nature.
plasticity is far too subtle a phenomenon to unambiguously support a more constrained or unconstrained view of human nature, because in fact it contributes to both human rigidity and flexibility, depending upon how it is cultivated.
