学会如何学习

Welcome to 'learning how to learn'. My name is Terry Sejnowski. Let me introduce you to your brain.

　　欢迎来到“如何学习”这门课 我是特里·谢诺沃斯基 (Terry Sejnowsky) 我来给大家介绍一下人脑。

　　First, some brain surgery. We take off the skull and take out the brain.首先，我来做个“脑外科手术”， 打开这个模型的颅骨，取出大脑。



　　This brain weighs three pounds, but it consumes ten times more energy by weight than the rest of the body, a very expensive organ. It is the most complex device in the known universe. All of your thoughts, your hopes, your fears are in the neurons in this brain.

　　人脑重约3磅。但按照质量来算，其消耗的能量比身体其他部分高10倍，是个奢侈的器官。它是已知宇宙中最复杂的设备，大脑神经元储存着人们所有的思想、希望和恐惧。

　　We prize our abilities to do chess and math, but it takes years of practice to acquire these skills. And digital computers are much better at it than we are. It came as a surprise to discover that what we do so well and take for granted, like seeing, hearing, reaching, running, are all much more complex problems than we thought and way beyond the capability of the world's fastest digital computers. 棋艺与算术称得上是人类的瑰宝，但需要多年的练习来获得这些技能。 然而，电子计算机在这两点上要比人类高明得多。[然而，]我们惊讶地发现：看、听、抓、跑等我们以为理所当然的动作，要比我们想象的复杂得多。世界上运行最快的计算机都难以做到。

　　What this illustrates is that we are not consciously aware of how our brains work. Brains evolved to help us navigate complex environments, and most of the heavy lifting is done below our level of consciousness. And we don't need to know how it's done in order to survive. 这说明我们并没有真正意识到大脑是如何工作的。大脑的进化使我们能驾驭复杂的环境，且大多数繁重的工作是在潜意识中完成的。我们并不需要知道大脑潜意识的工作机理才能生存下去[，这一切都是自然而然的]。

　　Psychologists who study the unconscious mind have found that influences include thought processes, memory, emotions and motivation. 研究潜意识的心理学家已经发现，影响 (大脑运作的) 因素包括思考过程、记忆、情绪和动机。

　　We are only aware of a very small fraction of all of the activity in the brain, so we need to rely on brain imaging techniques to guide us.[目前科技的发展]仅仅令人们认识到课脑部活动的一小部分，所以进一步的而研究有赖于脑部成像技术的指引。

　　Here is the activity map of someone's brain who was asked to lie still, at rest, in a brain imaging scanner. On the left is the side view of the brain and on the right is the view from the midline. 这是一张大脑活动图。被测者按照要求平静地躺在脑部扫描仪下，左边是大脑的侧视图，右边是剖面图。


　　The colors indicate brain areas whose activities were highly correlated, as shown by the time courses below, color-coded to the brain areas.颜色指示的大脑区域。其活动与下方所示的时相图高度相关，也就是图示中大脑着色部分。

　　The blue areas are highly active when the subject interacts with the world, but turn off in a resting state. 当被测者与外界互动时，蓝色区域高度活跃，在静息状态下则无反应。

　　The red-orange areas are most active in the resting state and are called the default mode network. Other brain areas are also more active when you are resting, and these areas can be further divided into groups of areas that have common patterns of activity. This is a new and intense area of research, and it will take time to sort out all the resting states and their functions. 橙红色区域在静息状态下最活跃，我们叫它脑默认网络。当你休息时，其他脑区域也同样很活跃。这些区域可进一步分成几组，每组有不同的活动模式。这个研究领域是个新兴热点，要想弄清楚所有的静息状态及其功能尚需时日。

　　There are a million billion synapses in your brain where memories are stored. The old view of the brain is that once it matures, the strengths of synapses can be adjusted by learning, but the pattern of connectivity does not change much unless there is brain damage. But now we know that brain connectivity is dynamic and remains so even after it matures.人的记忆存储在亿万个神经突触里，传统观点认为，大脑一旦发育成熟，突触可以通过学习增强。但除非脑部受到重创，否则认知模式无法改变。而现在我们知道，大脑在成熟以后，其脑连接依然处于动态。

　　With new optical techniques for imaging single connections between neurons called synapses, we can see constant turnover, with new synapses being formed and others disappearing. This raises a puzzle. In the face of so much turnover, how do memories stay stable over so many years? This is a picture of one dendritic branch on a neuron which receives inputs from other neurons. The synapses are on the spiny knobs coming off the dendrite. On the top, the dendrite was imaged before learning. The same dendrite is shown below after learning and after sleep. Multiple synapses that are newly formed together on the same branch are indicated by the white arrowheads. You are looking down into the brain of a live animal. This is really a fantastic new technique. 随着新的光学成像技术的出现，单个神经元之间的连接，即突触，可以被观测到。我们可以看到突触的更迭，新突触形成伴随着旧突触的消失。由此便产生了一个疑问：突触新旧更替，为何记忆能在多年内保持稳定？ 这是神经元的一个树突分支的图片，它负责接收来自于其他神经元的信息。树突上的那些刺一样的突起就是突触。学习之前的树突如上图所示，下图是经过学习和睡眠后的同一个树突，白色箭头标明的是同一树突分支上一起形成的多个新突触。你看的是一个活体动物大脑的内部，这真是一项非常强大的新技术。


　　Synapses are less than a micron in diameter. In comparison, a human hair is around 20 microns in diameter.

　　突触直径不足1微米，相较之下，人类头发直径约20微米。


　　This new technique allows us to see how learning changes the structure of the brain with a resolution that is near the limit of light microscopy. 这项新技术使我们能观察到学习如何改变脑部结构，分辨率几乎达到光学显微镜的极限。

　　This illustrates that, intriguingly, that you are not the same person you were after a night's sleep or even a nap. It is if you went to bed with one brain and woke up with an upgrade. This is a better deal than you can get from Microsoft. Shakespeare, the great English poet, already knew this. 这说明了有趣的一点：睡一觉甚至打个盹，你就不再是原来那个自己了。也就是说，一觉过后你的大脑就升级了。比你能从Microsoft那里得到的升级更加优越，英国伟大诗人莎士比亚早就知道这点了。


　　Here is Macbeth lamenting his insomnia. 这是麦克白对失眠的悲叹——

　　Sleep that knits up the raveled sleeve of care, the death of each day's life, sore labor's bath, balm of hurt minds, great nature's second course, chief nourisher in life's feast. '睡眠，编织缠绕的愁绪，如今日之死，涤去疲惫' '受伤心灵的良药，大自然馈赠的佳肴' '生命盛筵的最佳滋补品'

　　Here Shakespeare is making an analogy between knitted clothes and sleep that knits up the loose threads of experience and concerns during the day and weaves them into the tapestry of your life story. You will learn in this first week how to take advantage of your unconscious mind, and also sleep, to make it easier to learn new things and solve problems. 莎士比亚在这里把睡觉比作织布，把白天的经历与担忧比作松散的线。正是睡眠将它们编织成描绘着你人生故事的锦绣。在第一周你将学习如何利用潜意识和睡眠。让学习新事物和解决问题变得更容易。

　　During the lectures you may ask yourself, how does the brain do this? A good place to find out more about your brain is the website brainfacts.org, brainfacts, one word, .org. You will find a wealth of interesting things about brains and behavior, and in particular about learning and memory. I am Terry Sejnowski. Happy learning until we meet again.