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The Question for Merzenich was, how does this topographic order emerge in the brain map? The answer he and his group came to was ingenious. A topographic order emerges because many of our everyday activities involve repeating sequences in a fixed order. When we pick up an object the size of an apple or baseball, we usually grip it first with our thumb and index finger, then wrap the rest of our fingers around it one by one. Since the thumb and index finger often touch at almost the same time, sending their signals to the brain almost simultaneously, the thumb map and the index finger map tend to form close together in the brain. (Neurons that fire together wire together.) As we continue to wrap our hand around the object, our middle finger will touch it next, so its brain map will tend to be beside the index finger and farther away from the thumb. As this common grasping sequence --- thumb first, index inter second, middle finger third --- is repeated thousands of times, it leads to a brain map where the thumb map is next to the index finger map, and so on. Signals that tend to arrive at separate times, like thumbs and pinkies, have more distant brain maps, because neurons that fire apart wire apart.

但是这个例子并不能解释topographic的概念。只有触觉和和人的身体结构有关的，所以存在空间上的相关性，但是很多其他的感官不存在空间性，那么这些感官在中枢里使如何排列的呢？再以味觉和嗅觉为例。人吃东西的时候同时受多种味道的刺激，大脑是如何分辨不同的味道的呢？大脑皮层上是不是有不同的区域对应不同的味觉？那些味觉在大脑中是相邻的？为什么它们相邻？等等。这些问题都不能用简单的topographic来解释。

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In one ingenious experiment, Merzenich mapped a normal monkey's hand, then sewed together two of the monkey's fibers, so that both fingers moved as one. After several months of allowing the monkey to use its sewn figures, the monkey was remapped. The two maps of the originally separate fingers had now merged into a single map. If the experimenters touched any point on either finger, this new single map would light up. Because all the movements and sensations in those fingers always occurred simultaneously, they'd formed the same map. The experiment showed that timing of the input to the neurons in the map was the key to forming it --- neurons that fired together in time wired together to make one map.

这个实验设计的有缺陷，并不能证明“fire together, wire together”. 假设有两根不相连的手指，比如大拇指和无名指被同时刺激，是否他们的brain map也会组合成一片？在这个实验里时间并不是唯一的因素，两根手指位置上的相邻也是有作用的。我很难想像同时刺激一个人的舌头和手指能够使这两部分感官相对应的中枢连成一片，以造成触摸手指引起酸甜苦辣的感觉。如果能造成这样的结果，那减肥就是小菜一碟了。口腹之欲可以通过进食之外的其他途径解决。

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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.

所以辞了职脑袋也不能闲着呀。刘冬梅同志！

Competitive plasticity in adults even explains some of our limitations. Think of the difficult most adults have in learning a second language. The conventional view now is that the difficulty arises because the critical period for language learning has ended, leaving us with a brain too rigid to change tis structure on a large scale. But the discovery of competitive plasticity suggests there is more to it. As we age, the more we use our native language, the more it comes to dominate our linguistic map space. Thus it is also because our brain is plastic --- and because plasticity is imputative --- that it is so hard to learn a new language and end the tyranny of the mother tongue.

But why, if there is true, is it easier to learn a second language when we are young? Is there not competition the too? Not really. If two languages are learned at the same time, during the critical period, both get a foothold. Brain scans, says Merzenich, show that in a bilingual child all th sounds of its two languages share a single large map, a library of sounds from both languages.

Competitive plasticity also explains why our bad habits are so difficult to brake 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 other a lot harder than learning, and why early childhood educate is so important --- it's best to get it right early, before the "bad habit" gets a competitive advantage. 

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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 processing 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".

这对人类来说是一种优势呀！No brain power is wasted.

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For people, postmortem examinations have shown that education increases the number of branches among neurons. An increased the number of branches among neurons. An increased number of branches drives the neurons father 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.

所以要想一直具有活跃的思维真的是要活到老，学到老！

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“The cerebral cortex,” he says of the thin outer layer of the brain, "is actually selectively refining its processing capacities to fit each task at hand." It doesn't simply learn; it is always "learning how to learn." The brain Merzenich describes is not an inanimate vessel that we fill; rather it is more like a living creature with an appetite, one that can grow and change itself with proper nourishment and exercise. Before Merzenich's work, the brain was seen as a complex machine, having unalterable limits on memory, processing speed, and intelligence. Merzenich has shown that each of these assumptions is wrong.

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They also discovered that there was a "critical period", from the third to the eight 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 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. Clearly the brains of kittens during the critical period were plastic, their structure literally shaped by experience.

看来“少壮不努力，老大徒伤悲”还有另外一种解释。学习要趁早不是“推”，而是人的生理基础决定的必然规律。

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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.

如果这些记忆或是思维活动能重新被激活，那真是激动人心的成果！人类的多愁善感会有很多新的蔓延领域，或是有很多本来存在的多愁善感就因此萎缩了。哈哈

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Merzenich claims that when learning occurs in a way consistent with the laws that govern brain plasticity, the mental "machinery" of the brain can be improved so that we learn and perceive with greater precision, speed, and retention.

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Enriched environments and stimulation lead the brain to grown. Over the years his labs and others have shown that stimulating the brain makes it grown in almost every conceivable way. Animals raised in enriched environments --- surrounded by other animals, objects to explore, toys to roll, ladders to climb, and running wheels --- learn better than genetically identical animals that have been reared in impoverished environments. Acetylcholine, a brain chemical essential for learning, is higher in rats trained on difficult spatial problems than in rats trained on simple problems. Mental training or life in enriched environments increases brain weight by 5 percent in the cerebral cortex of animals and up to 9 percent in areas that the training directly stimulates. Trained or stimulated neurons develop 25 percent more branches and increase their size, the number of connections per neuron, and their blood supply. These changes can occur late in life, though they do no develop as rapidly in older animals as in younger ones. Similar effects of training and enrichment on brain anatomy have been seen in all types of animals tested to date.

孟母三迁的生理学原因。看来创造环境对孩子的成长是十分必要，也是非常重要的。

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Barbara Arrowsmith Young's work compels us to imagine how much good might be accomplished if every child had a brain-based assessment and, if problems were found, a tailor-made program created to strengthen essential areas in the early years, when neuroplasticity is greatest. 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 working in the weakened area, losing whatever strength he may have. Younger children often progress more quickly through brain exercises than do adolescents, perhaps because in an immature brain the number of connections among neurons, or synapses, is 50 percent greater than in adult brain. When we reach adolescence, a massive "pruning back" operation begins in the brain, and synaptic connections and neurons that have not been used extensively suddenly die off --- a classic case of "use it or lose it". it is probably best to strengthen weakened areas while all this extra cortical real estate is available. Still, brain-based assessments can be helpful all through school and even in college and university, because their week brain functions are overloaded by the increased demand. Even apart from these crises, every adult could benefit from a brain-based cognitive assessment, a cognitive fitness test, to help them better understand their own brain.

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"I knew that the words 'mother' and 'daughter' meant but no the expression 'mother's daughter,'" Zazetsky wrote, "The expressions 'mother's daughter' and 'daughter's mother' sounded just the same to me. I also had trouble with expressions like 'Is an elephant bigger than a fly?' All I could figure out was that a fly was small and an elephant is big, but I didn't understand the words 'bigger' and 'smaller.'"

......

She isolated herself and began toiling to the point of exhaustion, week after week --- with only brief breaks for sleep --- at mental exercises she designed, though she had no guarantee they would lead anywhere.

有时候一个人有缺陷或是残疾，或者遇到巨大的困难，或是处于特别无助的境地，这些劣势会激发出人深藏的潜力，反倒创造出比健康人或身处顺境的人要好得多的成绩来。

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George knew nothing about rehabilitation, and his ignorance turned out to be a godsend, because he succeeded by breaking all its current rules, unencumbered by pessimistic theories.