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In week zero, when we tore the phonebook in half and half and half we were recursing through that problem.
当我们将电话簿划分为一半又一半的时候,其实就是利用递归在解决问题。
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Well, the infinity mechanism, and many of you will be familiar with this from mathematics or computer science, is recursion.
这种无限机制是递归的,你们许多人会在数学与计算机科学中,熟悉这个词
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And I will briefly touch upon these wonderful systems that are able to deliver information into the brain and nerve system.
我会简要提及这些能够向大脑和神经系统,递信息的美妙系统。
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What's the point of this? Again, now that I can think about things recursively, I can similarly break things down into simpler versions of the same problem. It could be one version.
这些的意思是什么呢？再一次我想说,我既然能够以递归的方式思考了,那么我就可以简单地把问题,转化为更简单的同类问题。
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So, the curious thing about recursion is that pretty much always can you implement this idea of doing the same thing again and again and again but with smaller bytes each time.
可见，递归算法中新奇的一点是,为了实现一个想法,你可以一遍又一遍地做相同的事情,但每次的规模都会有所减小。
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But in general, for each neurotransmitter that released it there would only be one population of receptors that's ready to receive it.
但总体说,每一种在此释放的神经递质,只能被一类受体接受
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At that fateful moment, Adam and Eve are standing together at the tree, and although only the woman and the serpent speak, Adam was present, and it seems he accepted the fruit that his wife handed him.
在那非同寻常的时刻，亚当和夏娃一起站在树下,尽管，只有女人和蛇在说话，但是亚当确实在场,而且接受了妻子递过来的果实。
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This sentence expands to a noun followed by a verb followed by a sentence and there you get recursion.
这个句子就扩展成了,一个名词,后跟一个动词,再接刚才的句子,这样就变成了递归
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But that's also nice, it lets you see how the recursive thing is simply unwrapping but the complexity in terms of the amount of time it takes is going to be the same.
它让我们看到了，在复杂度依照时间总数来看,没有变化的情况下,递归是怎么一步步的展开的,我欠你一个糖，谢谢。
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And I'm going to show you an example in a 1 second, just to drive this home, but notice the characteristics. In the first two cases, the problem reduced by 1 at each step.
在前面两个例子里,每一部问题的规模缩小了,不管是迭代的还是递归的，这表明这个问题的复杂性可能是线性的。
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When we discuss clinical psychology and depression we'll learn the extent to which neurotransmitter disorders are implicated in certain disorders like depression.
等我们探讨临床心理学以及抑郁症的时候,就会知道神经递质代谢障碍,对抑郁症这样的心理障碍的影响程度了
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And one problem is that "For depression" is that there's too little of a neurotransmitter known as serotonin.
抑郁症的问题就在于,缺乏一种叫做血清素的神经递质
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- So this is where recursion gets a little trippy-- certainly initially, and that you have to kind of keep diving deeper, deeper, deeper into the problem.
在这儿就会觉得递归有点迷糊了-,起初，你必须一层一层地,深入到问题中。
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Because if it was a neurotransmitter activated ion channel, what would happen when the neurotransmitter bound here?
因为假如这是一个,神经递质激活的离子通道,当神经递质结合于此的时候,会发生些什么呢
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There are two sorts of ways you could fiddle with neurotransmitters, and correspondingly two sorts of drugs.
你可以通过两种方式来控制神经递质,相应地,也就有两种对应的药物
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So, that process happens fast but you also need this neurotransmitter release and activation to happen fast so that you can have rapid activity.
所以 电传递过程很快,但你仍需要神经递质的,快速释放和快速激活,以便使你快速活跃起来
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Because the algorithm I proposed is going to leverage this idea of recursion which recall was just a piece of jargon we tossed out at the last-- at the end of last week's lecture, last time's lecture recursion really in this context refers to the act of a function calling it's self.
因为我提出的这种算法使用了,递归的思想，这是上周课程的最后,所提出的一个术语，上次的课程中，递归是指,函数的自我调用。
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And the reason I want to show you this is to notice that the recursion can be doubled.
如果我来写斐波那契数列你可以看看这儿,原因是我想让你看看这部分的递归可以翻倍。
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All right, this is what's called a recurrence relation, there are actually cool ways to solve them. We can kind of eyeball it.
好，这就是所谓的递归关系,也就是解决问题的相当好的办法,我们可以来看看。
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But I want to stress again, as long as I do the base case right and my inductive or recursive step reduces it to a smaller version of the same problem, the code will in fact converge and give me out an answer.
就开心的去做吧,但是我想再次强调,只要基础事件处理正确而我的递归,或递推步骤能把它简化为更简单的同类问题,那么这段代码就可以收敛。
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We're going to see variations of this, we're going to see a variation of it called recursion, a little later on, but for now we're just going to talk about how do we do iterations.
我们稍后会去，看它的变量,它的所谓的递归数的变量，但是现在我得先讲讲,怎么来实现迭代。
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Not so easy to see. All right, but this is actually a great one of those educational moments. This is a great example to think recursively. If I wanted to think about this problem recursively- what do I mean by thinking recursively?
看不太出来，好，但实际上是一个有教育意义的时刻,这是一个很好的关于递归的例子,如果我用递归的思想,去考虑这个问题-,我该怎么用递归去解决这个问题呢？
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Then, there are antagonists that slow down the amount of neurotransmitters, either because they destroy neurotransmitters or they make it hard to create more.
另一种是抑制剂,抑制剂会抑制神经递质的释放量,有可能是通过破坏神经递质而实现,也可能是通过抑制神经递质的生成而实现
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In particular, they increase the amount of norepinephrine, a neurotransmitter that's responsible for just general arousal.
具体来说,安非他命会引起,去甲肾上腺素释放量的增加,去甲肾上腺素,是种负责一般性唤醒的神经递质
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Or in some cases they go to the dendrite of the neuron and they kind of put a paste over it so that the neurotransmitters can't connect.
有时这些药物会渗透到神经元的树突,这些药物就像是在树突上涂了一层涂料,使得神经递质无法将树突与轴突相连
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Many neurotransmitters that carry signals between neurons in your brain work this way.
在脑部神经元细胞中,传递信号的神经递质分子的,作用原理就是如此
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All right, any questions about that. Yeah?
递归调用来解决其他问题？
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Neurotransmitters are molecules you've heard of like acetylcholine, like dopamine, like serotonin.
一些神经递质分子 你们可能听说过,像乙酰胆碱,多巴胺,血清素
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How many of you have heard the term used before? How may have you heard the term used before in terms of programming languages? Great. For the rest you, don't sweat it. This is a highfalutin term that computer scientists use to try and make them look like they're smarter than they really are.
这里就要引入递归的概念了,你们中有多少人以前听过这个词？,你们中有多少人在编程语言中,用过这个词？,很好，剩下的同学也不要担心,这是电脑科学家们用来让自己,显得更聪明的夸张词汇。
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It's actually a wonderful recursive definition.
这就是一个绝妙的递归定义。
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