Sarah-Jayne Blakemore: The mysterious workings of the adolescent brain

Translator: Joseph Geni Reviewer: Morton Bast

翻译人员: Li Li 校对人员: Yi Zong

Fifteen years ago, it was widely assumed

15年前，大多数人认为

that the vast majority of brain development

人类大脑最重要的发育阶段

takes place in the first few years of life.

是在生命开始的头几年进行的

Back then, 15 years ago, we didn't have the ability

在过去，15年前，我们还做不到

to look inside the living human brain

探究人脑的内部活动的情况

and track development across the lifespan.

以及追踪它在生命中的发育过程。

In the past decade or so, mainly due to advances

在过去10年左右，主要是依靠

in brain imaging technology

脑成像技术的发展

such as magnetic resonance imaging, or MRI,

像磁共振成象，简称MRI，

neuroscientists have started to look inside the living

神经科学家已经开始了探究不同年龄

human brain of all ages, and to track changes

的人脑内部情况，并记录下大脑结构和功能

in brain structure and brain function,

的不同变化，

so we use structural MRI if you'd like to take a snapshot,

如果需要生成影像，我们可以使用结构磁共振成像，

a photograph, at really high resolution of the inside

可以拍出高分辨率的人脑内部图

of the living human brain, and we can ask questions like,

这样我们就可以提出一些问题了，例如

how much gray matter does the brain contain,

大脑里有多少脑灰质

and how does that change with age?

会随着年龄变化而变化吗？

And we also use functional MRI, called fMRI,

我们也可以使用功能磁共振成像，简称fMRI

to take a video, a movie, of brain activity

它可以拍摄视频，这样就可以在试验者

when participants are taking part in some kind of task

进行某项活动中，比如思考或感受某些东西时

like thinking or feeling or perceiving something.

记录拍摄下大脑的活动情况。

So many labs around the world are involved in this kind

现在世界上很多实验室都参与了这项研究

of research, and we now have a really rich

所以我们就得出了很丰富

and detailed picture of how the living human brain develops,

很详尽的图片，解密了人脑的发育情况

and this picture has radically changed the way

同时这张照片从根本上颠覆了

we think about human brain development

我们以往对人脑发育的观念

by revealing that it's not all over in early childhood,

通过告诉我们发育的过程不完全都在幼儿阶段

and instead, the brain continues to develop

相反，大脑会继续发育

right throughout adolescence and into the '20s and '30s.

贯穿整个青春期，一直到20多岁甚至30多岁

So adolescence is defined as the period of life that starts

所以青春期也被定义为

with the biological, hormonal, physical changes of puberty

生命中生理和荷尔蒙转变的开端

and ends at the age at which an individual attains

当人们在社会中获得一个稳定和独立的身份时

a stable, independent role in society.

也就标志这青春期的结束了。

(Laughter)

（笑声）

It can go on a long time. (Laughter)

有时青春期会持续很久很久。（笑声）

One of the brain regions that changes most dramatically

大脑其中的一个区域，叫前额叶皮层，

during adolescence is called prefrontal cortex.

它在青春期阶段是最活跃的。

So this is a model of the human brain,

这个是人脑的一个模型

and this is prefrontal cortex, right at the front.

这里是前额叶皮层，就在前面这里

Prefrontal cortex is an interesting brain area.

前额叶皮层是非常有意思的一个大脑区域

It's proportionally much bigger in humans than

相对其他物种而言

in any other species, and it's involved in a whole range of

人类的前额叶皮层是大很多的

high level cognitive functions, things like decision-making,

它涉及到大量的高级认知功能 ，例如决策

planning, planning what you're going to do tomorrow

计划，计划明天要做的事情

or next week or next year, inhibiting

或者下周或明年的

inappropriate behavior, so stopping yourself saying

对不恰当行为的抑制，像阻止你

something really rude or doing something really stupid.

说一些粗鲁的话或做一些傻事

It's also involved in social interaction,

它还涉及到社交方面

understanding other people, and self-awareness.

包括理解他人和自我意识

So MRI studies looking at the development of this region

所以MRI对前额叶皮层的发育的研究

have shown that it really undergoes dramatic development

揭示了它确实在青春期阶段

during the period of adolescence.

有着非同寻常的发育情况

So if you look at gray matter volume, for example,

举个例子，如果你去看大脑灰质

gray matter volume across age from age four to 22 years

从4岁起到22岁的大脑灰质

increases during childhood, which is what you can see

会在童年时期会增加，也就是现在在图表上你能看到的

on this graph. It peaks in early adolescence.

在早期的青春期会到达顶峰

The arrows indicate peak gray matter volume

箭头指的就是大脑灰质在前额叶皮层

in prefrontal cortex. You can see that that peak happens

达到的锋点，你会发现要达到这个锋点

a couple of years later in boys relative to girls,

男孩会相对比女孩要慢几年

and that's probably because boys go through puberty

这大概是因为男孩平均要比女孩

a couple of years later than girls on average,

晚那么几年经历青春期

and then during adolescence, there's a significant decline

在青春期阶段，大脑灰质

in gray matter volume in prefrontal cortex.

在前额叶皮层会出现一个明显的下降

Now that might sound bad, but actually this is

听起来似乎有些不安

a really important developmental process, because

但这确实一个极其重要的发育阶段

gray matter contains cell bodies and connections

因为大脑灰质包涵了细胞体

between cells, the synapses, and this decline

还有细胞之间的联系，也就是突触

in gray matter volume during prefrontal cortex

在前额叶皮层到了一个需要对突触进行修剪

is thought to correspond to synaptic pruning,

去除掉一些不必要的突触的这一阶段

the elimination of unwanted synapses.

大脑灰质也就会减少

This is a really important process. It's partly dependent

这是非常关键的阶段

on the environment that the animal or the human is in,

一部分取决于动物或人类居住的环境

and the synapses that are being used are strengthened,

那些有价值的突触会茁壮发育

and synapses that aren't being used

而在那个特定的环境里

in that particular environment are pruned away.

那些没什么存在必要的突触则会被剔除掉

You can think of it a bit like pruning a rosebush.

你可以把它当成是修剪盆栽

You prune away the weaker branches so that

把那些奄奄一息的枯枝败叶修剪掉

the remaining, important branches, can grow stronger,

这样那些剩下的，重要的枝干，就会茁壮成长

and this process, which effectively fine-tunes brain tissue

这个会根据物种及环境不同

according to the species-specific environment,

而高效调整大脑组织的过程

is happening in prefrontal cortex and in other brain regions

就是在人类的青春期阶段

during the period of human adolescence.

在前额叶皮层和其他大脑区域进行的

So a second line of inquiry that we use to track changes

我们用来记录青春期大脑变化

in the adolescent brain is using functional MRI

的第二轮调查，就是用功能磁共振成像

to look at changes in brain activity across age.

来探究不同年龄大脑活动的变化情况

So I'll just give you an example from my lab.

这里我举个发生在我实验室里的例子。

So in my lab, we're interested in the social brain, that is

在我的实验室里，我们对社会大脑很感兴趣，

the network of brain regions that we use to understand

就是我们与他人沟通交流

other people and to interact with other people.

的大脑区域网络。

So I like to show a photograph of a soccer game

我会给你们看一张足球赛的图片

to illustrate two aspects of how your social brains work.

跟你们分析下社会性大脑工作时的两个方面

So this is a soccer game. (Laughter)

这就是一场足球赛。（笑声）

Michael Owen has just missed a goal, and he's lying

迈克尔欧文刚刚的射门没有命中，

on the ground, and the first aspect of the social brain

所以他躺在地上，这张图片诠释了

that this picture really nicely illustrates is how automatic

社交情绪反应是多么自动自觉的

and instinctive social emotional responses are,

这是社会脑的第一个层面，

so within a split second of Michael Owen missing this goal,

所以就在欧文没射中球门的那一瞬间，

everyone is doing the same thing with their arms

每个人的手都是同样的动作

and the same thing with their face, even Michael Owen

同样的表情，甚至欧文也是这样

as he slides along the grass, is doing the same thing

在他划过草地时，他也是同样的手势

with his arms, and presumably has a similar

估计他的面部表情也差不多

facial expression, and the only people who don't

而唯一不为所动的那个人，

are the guys in yellow at the back — (Laughs) —

就是背后穿黄色球衣的了——（笑声）——

and I think they're on the wrong end of the stadium,

我觉得他们是场上占不到什么优势的人

and they're doing another social emotional response

他们有着不一样的社交情绪反应

that we all instantly recognize, and that's the second aspect

我们能马上认出来，这就是社会脑的第二个层面

of the social brain that this picture really nicely illustrates,

也在图片上很好地表现出来

how good we are at reading other people's behavior,

它揭示了我们对他人行为的理解程度

their actions, their gestures, their facial expressions,

按照潜在的情绪和精神状态

in terms of their underlying emotions and mental states.

解读他人的举动，他人的手势，还有他们的面部表情

So you don't have to ask any of these guys.

所以你不用去问他们中的任何一人。

You have a pretty good idea of what they're feeling

就能对这个时候他们的情感和思想

and thinking at this precise moment in time.

有一个颇为准确的理解。

So that's what we're interested in looking at in my lab.

这就是我的实验室所感兴趣的事。

So in my lab, we bring adolescents and adults into the lab

在实验室里，我们召集了青少年和成年人

to have a brain scan, we give them some kind of task

进行大脑扫描，我们给他们分配任务

that involves thinking about other people, their minds,

涉及了他们对他人，自己的思想，自己的精神状态，

their mental states, their emotions, and one of the findings

以及对自己的情绪的思考

that we've found several times now, as have other labs

和其他实验室一样，目前我们多次发现的一点是

around the world, is part of the prefrontal cortex called

前额叶皮层的一个部分

medial prefrontal cortex, which is shown in blue on the slide,

叫做内侧前额叶皮质，就是蓝色那部分，

and it's right in the middle of prefrontal cortex

就在前额叶皮质的正中间

in the midline of your head.

在脑袋的正中央。

This region is more active in adolescents when they make

当青少年在做社交决定以及考虑他人时

these social decisions and think about other people

他们大脑的这个区域

than it is in adults, and this is actually a meta-analysis

要比成年人还要活跃，这其实是世界上其他实验室

of nine different studies in this area from labs around

在这个方面的九个不同研究的荟萃分析

the world, and they all show the same thing, that activity

他们都表明了一样的结果，

in this medial prefrontal cortex area decreases

就是内侧前额叶皮质的活跃度，

during the period of adolescence.

会在青春期阶段逐渐减小。

And we think that might be because adolescents and adults

我们猜测可能是青少年和成年人

use a different mental approach, a different

在做社交决定时，有着不同的心理活动

cognitive strategy, to make social decisions,

不同的认知策略，

and one way of looking at that is to do behavioral studies

研究这个的方法之一就是采用行为研究

whereby we bring people into the lab and we give them

我们把人召集进实验室

some kind of behavioral task, and I'll just give you

分配给他们一些行动任务，

another example of the kind of task that we use in my lab.

我给你们举个我们实验室的任务的例子。

So imagine that you're the participant in one of our

想象一下你是我们实验的参与人员之一

experiments. You come into the lab,

你进到这个实验室，

you see this computerized task.

你看到这个电脑程序任务。

In this task, you see a set of shelves.

在这个任务中，你看到几排的架子。

Now, there are objects on these shelves, on some of them,

现在架子上有些摆上了物品，

and you'll notice there's a guy standing behind the set

你会发现有个人站在架子后面，

of shelves, and there are some objects that he can't see.

而且有些物品他是看不到的。

They're occluded, from his point of view, with a kind of

他们被遮住了，从这个角度看

gray piece of wood.

被灰色的木板遮住了。

This is the same set of shelves from his point of view.

从他的角度看，这是同样的架子。

Notice that there are only some objects that he can see,

但要注意，他只看得到一些物品，

whereas there are many more objects that you can see.

但你却能看到更多的。

Now your task is to move objects around.

你的任务就是去移动这些物品。

The director, standing behind the set of shelves,

引导人员，将站在架子后面，

is going to direct you to move objects around,

引导你去移动这些物品，

but remember, he's not going to ask you to move objects

但是要记住，他不会叫你去移动那些

that he can't see. This introduces a really interesting

他看不到的物品。这就引出了一个很有意思的情况

condition whereby there's a kind of conflict

在你的角度和引导员的角度之间

between your perspective and the director's perspective.

会有一种冲突。

So imagine he tells you to move the top truck left.

假设他叫你去把上面的火车往左移。

There are three trucks there. You're going to instinctively

但那儿有三辆火车，你会很自然地

go for the white truck, because that's the top truck

去移动白色那辆，因为从你的角度看

from your perspective, but then you have to remember,

它就是上面的火车，但你得知道

"Oh, he can't see that truck, so he must mean

“噢，他看不见那辆火车，所以

me to move the blue truck," which is the top truck

他是想我去移动蓝色的，”就是他的角度

from his perspective. Now believe it or not,

最上面的那辆。现在信不信由你，

normal, healthy, intelligent adults like you make errors

像你们一样正常健康聪明的成年人都会犯错

about 50 percent of the time on that kind of trial.

在这种试验中，犯错几率高达50%。

They move the white truck instead of the blue truck.

他们会移动白色那辆，而不是蓝色那辆

So we give this kind of task to adolescents and adults,

话说我们给青少年还有成年人分配了这种任务，

and we also have a control condition

我们有条件控制

where there's no director and instead we give people a rule.

一个是没有引导员，另一个是给他们定规则。

We tell them, okay, we're going to do exactly the same thing

我们告诉他们，好吧，我们会做一样的事情

but this time there's no director. Instead you've got to

这次没有引导员。

ignore objects with the dark gray background.

相反，你得忽略那些灰色格子。

You'll see that this is exactly the same condition, only

你会发现其实条件是完全一样的，

in the no-director condition they just have to remember

要记住没有引导员这一情况

to apply this somewhat arbitrary rule, whereas

只有规定的要求，

in the director condition, they have to remember

但在有引导员的情况下，他们则需要

to take into account the director's perspective

考虑引导员的视野角度

in order to guide their ongoing behavior.

这样才能理解引导员的指令。

Okay, so if I just show you the percentage errors

这个就是在我们较大规模的研究中

in a large developmental study we did,

得出的犯错比率，

this is in a study ranging from age seven to adulthood,

这是从七岁到成年的一个研究，

and what you're going to see is the percentage errors

你们接下来会看到的就是成人组

in the adult group in both conditions,

在两种条件下的错误比率，

so the gray is the director condition, and you see

灰色的就是有引导员的情况，

that our intelligent adults are making errors about 50 percent

你会发现我们聪明的成年人的错误率约是50%

of the time, whereas they make far fewer errors

但是他们在没有引导员在场的情况下。

when there's no director present, when they just have

错误率会低很多，他们只需

to remember that rule of ignoring the gray background.

记住去忽略灰色格子这一规定。

Developmentally, these two conditions develop

相应地，这两种条件的情况

in exactly the same way. Between late childhood

发展几乎是一样的，在后儿童期

and mid-adolescence, there's an improvement,

还有中青春期，都是有所提升，

in other words a reduction of errors, in both of these trials,

换句话说，就是在这些试验中，在这些条件下，

in both of these conditions.

错误的几率会随年龄增加而减少。

But it's when you compare the last two groups,

但当你比较最后两组实验时，

the mid-adolescent group and the adult group

中青春期组和成年组

where things get really interesting, because there, there is

事情会变得有趣很多

no continued improvement in the no-director condition.

因为在没有引导员的情况下，也没有提升的趋势。

In other words, everything you need to do in order to

也就是说，涉及到记住规则并应用它所需要的一切

remember the rule and apply it seems to be fully developed

似乎都在中青春期已经尘埃落定了

by mid-adolescence, whereas in contrast,

但是相反地，

if you look at the last two gray bars, there's still

如果你去看两条灰色的图柱

a significant improvement in the director condition

在有引导员的条件下，在中青春期和成年组之间

between mid-adolescence and adulthood, and what

还是有明显的提升的

this means is that the ability to take into account someone

这就意味着，从他人角度考虑出发

else's perspective in order to guide ongoing behavior,

从而运用到实践中的能力，

which is something, by the way, that we do in everyday life all

而这也是我们日常生活随处可见的，

the time, is still developing in mid-to-late adolescence.

这一能力，在青春期的中后期仍在发育中。

So if you have a teenage son or a daughter and you

所以如果你有一个儿子或女儿出于青春期

sometimes think they have problems taking other people's

你有时觉得他们在考虑他人感受时做得不够好

perspectives, you're right. They do. And this is why.

那么你是对的，的确是这样，这就是原因。

So we sometimes laugh about teenagers.

所以我们有时会讽刺青少年。

They're parodied, sometimes even demonized in the media

说他们没什么大脑，有时会在媒体上

for their kind of typical teenage behavior. They take risks,

丑化他们那种典型的青春期行为，

they're sometimes moody, they're very self-conscious.

他们爱冒险，情绪阴晴不定，非常自我。

I have a really nice anecdote from a friend of mine

我从我朋友那儿听到一个很有趣的故事

who said that the thing he noticed most

他说这是他在女儿们

about his teenage daughters before and after puberty

青春期前后经常见到的事

was their level of embarrassment in front of him.

就是在他面前的尴尬程度。

So, he said, "Before puberty, if my two daughters

她说，“青春期前，如果我的两个女儿

were messing around in a shop, I'd say, 'Hey,

在商店里胡闹，我会说，嘿

stop messing around and I'll sing your favorite song,'

别闹了，我给你们唱你们最喜欢的歌，”

and instantly they'd stop messing around and he'd sing

然后她们立即安分守己，听他唱歌

their favorite song. After puberty, that became the threat.

但青春期过后，唱歌成了威胁。

(Laughter)

（笑声）

The very notion of their dad singing in public

他们爸爸在公众场合唱歌这一举动

was enough to make them behave.

足以震慑他们的调皮。

So people often ask,

所以人们经常问，

"Well, is adolescence a kind of recent phenomenon?

“那么，青春期是一种新生的现象吗？

Is it something we've invented recently in the West?"

是西方国家近几年才发现的吗？”

And actually, the answer is probably not. There are lots

其实，答案不然。历史上，

of descriptions of adolescence in history that sound

有过很多青春期的描写

very similar to the descriptions we use today.

与今天那些描述十分相似。

So there's a famous quote by Shakespeare from "The Winter's Tale"

莎士比亚的《冬天的故事》里有这么一段

where he describes adolescence as follows:

他是这么描述青春期的：

"I would there were no age between ten and

“孩子与成人之间不再有差别

three-and-twenty, or that youth would sleep out the rest;

年轻人要么就去安眠；

for there is nothing in the between but getting wenches

因为他们会空虚到

with child, wronging the ancientry, stealing, fighting." (Laughter)

与孩子滥交、做出伤风败俗的偷窃和斗殴。”（笑声）

He then goes on to say, "Having said that, would any

他接着说，“话虽如此，但除了那些十几二十岁

but these boiled brains of nineteen and two-and-twenty

的脑残少年，还有谁

hunt in this weather?" (Laughter)

会在这种天气出来打猎啊？”（笑声）

So almost 400 years ago, Shakespeare was portraying

所以约在400年前，莎士比亚

adolescents in a very similar light to the light that we

描述的青少年就十分类似我们今天所指的青少年

portray them in today, but today we try to understand

但如今我们尝试根据他们，

their behavior in terms of the underlying changes

大脑那些看不到的变化

that are going on in their brain.

去理解他们的行为。

So for example, take risk-taking. We know that adolescents

举个例子，爱冒险。我们知道青少年

have a tendency to take risks. They do.

有爱冒险的倾向，真的有的。

They take more risks than children or adults,

他们会比儿童或成人更爱冒险，

and they are particularly prone to taking risks

而且在和朋友在一起的时候

when they're with their friends. There's an important drive

会更有冒险倾向

to become independent from one's parents

在青春期会有个明显的驱动力

and to impress one's friends in adolescence.

就是远离父母争取独立和在朋友间出类拔萃。

But now we try to understand that in terms of

但现在我们根据他们大脑某部分叫边缘系统的发育

the development of a part of their brain called the limbic system,

尝试去理解他们，

so I'm going to show you the limbic system in red

我会在背后的幻灯片里

in the slide behind me, and also on this brain.

给你们看下红色的边缘系统，这个大脑里也有。

So the limbic system is right deep inside the brain,

边缘系统就在大脑的深处，

and it's involved in things like emotion processing

它涉及了情感处理还有奖励感处理

and reward processing. It gives you the rewarding feeling

在你做有趣的事情时，像冒险

out of doing fun things, including taking risks.

它会产生一种收获的感觉。

It gives you the kick out of taking risks.

它让你在冒险中产生快感。

And this region, the regions within the limbic system,

这部分区域，在边缘系统里的区域，

have been found to be hypersensitive to the rewarding

相比成年人，对青少年的冒险产生的收获感

feeling of risk-taking in adolescents compared with adults,

具有很高的敏感性，

and at the very same time, the prefrontal cortex,

与此同时，前额叶皮层，

which you can see in blue in the slide here,

在幻灯片显示蓝色的地方，

which stops us taking excessive risks,

会阻止我们过多地参与冒险，

is still very much in development in adolescents.

但在青春期还是出于发育阶段。

So brain research has shown that the adolescent brain

关于大脑的研究表明青少年的大脑

undergoes really quite profound development,

经历了意义深远的的发育，

and this has implications for education, for rehabilitation,

这对教育，康复和介入治疗方面，就有所启示了，

and intervention. The environment, including teaching,

环境，包括教学，

can and does shape the developing adolescent brain,

能塑造青少年大脑的发育，

and yet it's only relatively recently that we have been

而且是到相当近的一段时期

routinely educating teenagers in the West.

在西方才对青少年有常规的教育。

All four of my grandparents, for example, left school

就像，我的四个祖父母

in their early adolescence. They had no choice.

在青春期早期就辍学了，他们也是没办法的。

And that's still the case for many, many teenagers

目前世界上很多地方还是存在这样的情况

around the world today. Forty percent of teenagers

百分之四十的青少年

don't have access to secondary school education.

没有机会进入学校接受初中教育。

And yet, this is a period of life where the brain is

而且，这个时期，是大脑处于

particularly adaptable and malleable.

特别有可塑性的时期。

It's a fantastic opportunity for learning and creativity.

是学习和培养创新的绝好时机。

So what's sometimes seen as the problem

所以那些常被认为是青少年的问题的情况

with adolescents — heightened risk-taking, poor impulse

高度爱冒险，易冲动不受控制

control, self-consciousness — shouldn't be stigmatized.

自我为中心，这些都不应受到指责。

It actually reflects changes in the brain that provide

它实际是反映了大脑的变化

an excellent opportunity for education

为教育，社会发展

and social development. Thank you. (Applause)

提供了很好的机遇。谢谢。（掌声）

(Applause)

（掌声）