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成人大脑如何学新而不忘旧(上)
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学习新知识不易，记住旧知识就更难了。无论是大脑还是人工智能软件，任何成功的学习系统都必须在稳定性和灵活性之间取得恰到好处的平衡。
双语精读
How adult brains learn the new without forgetting the old
成人大脑如何学新而不忘旧
Learning new things is hard. Remembering what has already been learned is harder.
学习新知识不易，记住旧知识就更难了。
Any successful learning system, be it a brain or a piece of artificial-intelligence software, must strike the right balance between stability and flexibility.
无论是大脑还是人工智能软件，任何成功的学习系统都必须在稳定性和灵活性之间取得恰到好处的平衡。
It must be stable enough to remember important old things yet flexible enough to learn new ones without destroying old memory traces--preferably for as long as it exists.
这样的学习系统必须足够稳定，能够记住重要的旧知识，同时也需要相当灵活，以便在不破坏旧记忆痕迹的情况下学习新知识----最好在整个生命周期都能保持这种平衡。
Learning is a result of changes in the pattern of neural connectivity in the brain. Each connection between nerve cells, called a synapse, is a tiny gap between the ends of branches ramifying from such cells.
学习是大脑神经连接模式变化的结果。神经细胞之间的各个连接被称为突触，也就是这些细胞分枝末端之间的微小间隙。
Messages jump across these gaps in the form of molecules called neurotransmitters. Current estimates suggest there are 600 trillion synapses in a human brain. How, then, to deal with the stability-plasticity dilemma--particularly as brains age and, as it were, fill up?
信息以一种被称为"神经递质"的分子形式穿越这些间隙。目前据估计，人类大脑中有600万亿个突触。那么，我们该如何处理大脑稳定性和可塑性之间的两难呢----特别是在大脑不断老化，也可以说是被逐渐填满时？
Research by Dimitra Vardalaki, Kwanghun Chung and Mark Harnett at the Massachusetts Institute of Technology, just published in Nature, suggests one way is to preserve into adulthood a type of memory-forming synapse found in children.
麻省理工学院的迪米特拉·瓦达拉基、钟光勋和马克·哈内特近期在《自然》杂志上发表的研究提出，一种方法是将儿童时期一种形成记忆的突触一直保存到成年。
These are called silent synapses. Silent synapses - which, as their name suggests, transmit no signal from one nerve cell to another - are often found on the ends of slender, immature protrusions from nerve cells, called filopodia.
这些被保留下来的突触名为沉默突触。顾名思义，沉默突触不在神经细胞间传递信号，它们通常存在于神经细胞伸出的细长而未成熟的突起（称为丝状伪足）的末端。
Until now, it had been thought that these disappeared as a brain matured. But Drs Vardalaki, Chung and Harnett have shown not only that they are present in adulthood, but also that they are common, at least in mice.
在此之前，人们一直认为沉默突触会随着大脑的成熟而消失。但瓦达拉基、钟光勋和哈内特博士已经证明，至少在小鼠体内，它们不仅存在于成年期，而且还很常见。
Just over a quarter of the connections they sampled in adult mouse visual cortices were silent synapses on filopodia. And murine and human brains are sufficiently alike that something similar almost certainly applies to people.
他们从成年小鼠的视觉皮层中采样的连接中，略多于四分之一属于丝状伪足上的沉默突触。根据鼠脑和人脑之间的相似程度，几乎可以肯定人类大脑也有相似的现象。
词汇预习
particularly [高考]
美[pərˈtɪkjələrli] | 英[pəˈtɪkjələli]
adv. 特别；尤其；详细地
adulthood [高考]
美[əˈdʌlthʊd] | 英[ˈædʌlthʊd]
n. 成年
flexibility [高考]
美[ˌfleksə'bɪləti] | 英[ˌfleksə'bɪləti]
n. 灵活性；弹性；适应性；柔韧性
nerve [高考]
美[nɜːrv] | 英[nɜːv]
n. 神经；勇气；敏感处；叶脉；厚脸皮 v. 鼓起勇气
stability [高考]
美[stəˈbɪləti] | 英[stəˈbɪləti]
n. 稳定性；居于修道院
transmit [高考]
美[trænzˈmɪt] | 英[trænzˈmɪt]
vt. 传达；传染；传送；代代相传 vi. (以无线电或有线电的方式)发送信号
preserve [高考]
美[prɪˈzɜːrv] | 英[prɪˈzɜːv]
v. 保护；保存；保持 n. 禁猎区；蜜饯
flexible [高考]
美[ˈfleksəbl] | 英[ˈfleksəbl]
adj. 柔韧的；灵活的；易弯曲的；可变通的
intelligence [高考]
美[ɪnˈtelɪdʒəns] | 英[ɪnˈtelɪdʒəns]
n. 智力；智慧；才智；（尤指关于敌国的）情报
stable [高考]
美[ˈsteɪbl] | 英[ˈsteɪbl]
adj. 稳定的；安定的；可靠的 n. 马棚；马厩；一批人 v. 使（马）入厩；入马棚
artificial [高考]
美[ˌɑːrtɪˈfɪʃl] | 英[ˌɑːtɪˈfɪʃl]
adj. 人造的；虚伪的；武断的
software [高考]
美[ˈsɔːftwer] | 英[ˈsɒftweə(r)]
n. 软件
alike [高考]
美[əˈlaɪk] | 英[əˈlaɪk]
adj. 相似的；同样的 adv. 一样；以同样的方式
dilemma [高考]
美[dɪˈlemə] | 英[dɪˈlemə]
n. 困境；进退两难
only that [高考]
美[ˈonli ðæt] | 英[ˈəunli ðæt]
adv. 只是(要不是；要是没有)
fill up [高考]
美[fɪl ʌp] | 英[fil ʌp]
vt. 装满(填写；填充；填塞；堵塞)
gap [高考]
美[ɡæp] | 英[ɡæp]
n. 缺口；裂缝；差距；空白
slender [四级]
美[ˈslendər] | 英[ˈslendə(r)]
adj. 细长的；苗条的；微薄的；少量的
sufficiently [四级]
美[sə'fɪʃ(ə)ntli] | 英[sə'fɪʃ(ə)ntlɪ]
adv. 足够地；充分地
immature [四级]
美[ˌɪməˈtʃʊr] | 英[ˌɪməˈtjʊə(r)]
adj. 不成熟的
neural [四级]
美[ˈnʊrəl] | 英[ˈnjʊərəl]
adj. 神经的
learned [四级]
美[lɜːrnd , ˈlɜːrnɪd] | 英[lɜːnd , ˈlɜːnɪd]
adj. 有学问的；博学的
trillion [六级]
美[ˈtrɪljən] | 英[ˈtrɪljən]
n. 大量；兆；万亿 adj. 兆的
learning [专八]
美[ˈlɜːrnɪŋ] | 英[ˈlɜːnɪŋ]
n. 学问；学识；学习
preferably [考研]
美[ˈprɛfərəblɪ] | 英['prefrəblɪ]
adv. 更好地；宁可；宁愿
as it were [考研]
美[æz ɪt wə] | 英[æz it wɜ:]
可以说； 在某种程度上
重点讲解
How adult brains learn the new without forgetting the old
成人大脑如何学新而不忘旧
strike a balance between 在……之间达成平衡
【例】China needs to strike a balance between maintaining a relatively fast and stable development and making economic structural adjustment.
中国需要在保持经济相对快速稳定发展和调整经济结构之间取得平衡。
Learning new things is hard. Remembering what has already been learned is harder.
学习新知识不易，记住旧知识就更难了。
strike a balance between 在……之间达成平衡
【例】China needs to strike a balance between maintaining a relatively fast and stable development and making economic structural adjustment.
中国需要在保持经济相对快速稳定发展和调整经济结构之间取得平衡。
Any successful learning system, be it a brain or a piece of artificial-intelligence software, must strike the right balance between stability and flexibility.
无论是大脑还是人工智能软件，任何成功的学习系统都必须在稳定性和灵活性之间取得恰到好处的平衡。
strike a balance between 在……之间达成平衡
【例】China needs to strike a balance between maintaining a relatively fast and stable development and making economic structural adjustment.
中国需要在保持经济相对快速稳定发展和调整经济结构之间取得平衡。
It must be stable enough to remember important old things yet flexible enough to learn new ones without destroying old memory traces--preferably for as long as it exists.
这样的学习系统必须足够稳定，能够记住重要的旧知识，同时也需要相当灵活，以便在不破坏旧记忆痕迹的情况下学习新知识----最好在整个生命周期都能保持这种平衡。
trace v. & n.
1. 作动词
（1）查出；找到；发现
【搭配】trace sb/ sth (to sth)
【例】We finally traced him to an address in Chicago.
我们终于追查到他在芝加哥的一个地址。
（2）追溯；追究
【搭配】trace sth (back) (to sth)
【例】She could trace her family tree back to the 16th century.
她能把本族家谱追溯到16世纪。
2. 作名词，痕迹；遗迹；踪迹
【例】The ship had vanished without (a) trace.
那艘船消失得无影无踪。
Learning is a result of changes in the pattern of neural connectivity in the brain. Each connection between nerve cells, called a synapse, is a tiny gap between the ends of branches ramifying from such cells.
学习是大脑神经连接模式变化的结果。神经细胞之间的各个连接被称为突触，也就是这些细胞分枝末端之间的微小间隙。
as it were 可以说是，似乎就是；好像
（英文释义：You say as it were in order to make what you are saying sound less definite.）
【例】I'd understood the words, but I didn't, as it were, understand the question.
我理解了这些话，但实际上，我不理解这个问题。
【拓展】近义词组：in a way, to some extent, so to speak, in a manner of speaking
Messages jump across these gaps in the form of molecules called neurotransmitters. Current estimates suggest there are 600 trillion synapses in a human brain. How, then, to deal with the stability-plasticity dilemma--particularly as brains age and, as it were, fill up?
信息以一种被称为"神经递质"的分子形式穿越这些间隙。目前据估计，人类大脑中有600万亿个突触。那么，我们该如何处理大脑稳定性和可塑性之间的两难呢----特别是在大脑不断老化，也可以说是被逐渐填满时？
as it were 可以说是，似乎就是；好像
（英文释义：You say as it were in order to make what you are saying sound less definite.）
【例】I'd understood the words, but I didn't, as it were, understand the question.
我理解了这些话，但实际上，我不理解这个问题。
【拓展】近义词组：in a way, to some extent, so to speak, in a manner of speaking
Research by Dimitra Vardalaki, Kwanghun Chung and Mark Harnett at the Massachusetts Institute of Technology, just published in Nature, suggests one way is to preserve into adulthood a type of memory-forming synapse found in children.
麻省理工学院的迪米特拉·瓦达拉基、钟光勋和马克·哈内特近期在《自然》杂志上发表的研究提出，一种方法是将儿童时期一种形成记忆的突触一直保存到成年。
protrusion n. 凸出物; 凸起部分
【例】He grabbed at a protrusion of rock with his right hand.
他用右手抓住了一块凸起的岩石。
【拓展】protrude v. 突出；伸出；鼓出
【搭配】protrude (from sth) 从...中伸出来
【例】protruding teeth 龅牙
He hung his coat on a nail protruding from the wall.
他把上衣挂在凸出墙面的一根钉子上。
These are called silent synapses. Silent synapses - which, as their name suggests, transmit no signal from one nerve cell to another - are often found on the ends of slender, immature protrusions from nerve cells, called filopodia.
这些被保留下来的突触名为沉默突触。顾名思义，沉默突触不在神经细胞间传递信号，它们通常存在于神经细胞伸出的细长而未成熟的突起（称为丝状伪足）的末端。
protrusion n. 凸出物; 凸起部分
【例】He grabbed at a protrusion of rock with his right hand.
他用右手抓住了一块凸起的岩石。
【拓展】protrude v. 突出；伸出；鼓出
【搭配】protrude (from sth) 从...中伸出来
【例】protruding teeth 龅牙
He hung his coat on a nail protruding from the wall.
他把上衣挂在凸出墙面的一根钉子上。
Until now, it had been thought that these disappeared as a brain matured. But Drs Vardalaki, Chung and Harnett have shown not only that they are present in adulthood, but also that they are common, at least in mice.
在此之前，人们一直认为沉默突触会随着大脑的成熟而消失。但瓦达拉基、钟光勋和哈内特博士已经证明，至少在小鼠体内，它们不仅存在于成年期，而且还很常见。
sufficiently adv. 充分地，足够地
【例】Academics and employers are concerned that students are not sufficiently prepared for college courses.
学术界和用人单位都担心学生们对大学课程没有做好足够准备。
【拓展】sufficient adj. 足够的；充足的
【搭配】be sufficient (to do sth); be sufficient (for sth/ sb)
【例】These reasons are not sufficient to justify the ban.
这些理由不足以证明实施禁令有理。
suffice v. 足够，足以；满足……的需求
【例】Generally a brief note or a phone call will suffice.
通常写个便条或打个电话就足够了。
apply to 适用于，应用于
【例】The convention does not apply to us.
该协定对我们不适用。
Just over a quarter of the connections they sampled in adult mouse visual cortices were silent synapses on filopodia. And murine and human brains are sufficiently alike that something similar almost certainly applies to people.
他们从成年小鼠的视觉皮层中采样的连接中，略多于四分之一属于丝状伪足上的沉默突触。根据鼠脑和人脑之间的相似程度，几乎可以肯定人类大脑也有相似的现象。
sufficiently adv. 充分地，足够地
【例】Academics and employers are concerned that students are not sufficiently prepared for college courses.
学术界和用人单位都担心学生们对大学课程没有做好足够准备。
【拓展】sufficient adj. 足够的；充足的
【搭配】be sufficient (to do sth); be sufficient (for sth/ sb)
【例】These reasons are not sufficient to justify the ban.
这些理由不足以证明实施禁令有理。
suffice v. 足够，足以；满足……的需求
【例】Generally a brief note or a phone call will suffice.
通常写个便条或打个电话就足够了。
apply to 适用于，应用于
【例】The convention does not apply to us.
该协定对我们不适用。
课后练习
It is important for a learning system to ____.
A. be receptive to new knowledge
B. use technology to improve efficiency
C. preserve the old and absorb the new
D. enlarge its memory capacity
Which of the following is true about neural connectivity?
A. Learning speeds up the transmitting of messages in the brain.
B. Nerve cells are connected by joining up their branches.
C. Neurotransmitters carry messages between nerve cells.
D. The function of synapses changes as the brain ages.
According to the text, silent synapses ____.
A. cannot send messages between nerve cells
B. store the memory of childhood in the brain
C. indicate immaturity and injury of nerve cells
D. can enhance the flexibility of the brain
What can be learned about the brain of mouse?
A. It doesn’t have silent synapses when it matures.
B. Its visual function is dominated by silent synapses.
C. It has a structure similar to that of human brains.
D. It is less developed than the brain of human.