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Imagine going to post a comment on this video,
想象一下，你要在这个视频上发表评论，
but out of nowhere, your hand decides to slap you instead of typing.
但莫名奇妙的，你的手决定拍你而不是打字。
That's basically what happened to a 57-year-old woman in 1908.
这就是1908年一名57岁的妇女身上发生的事。
Much to her surprise, she was attacked by her left hand.
她很吃惊，她被自己的左手攻击了！
And the hand was persistent,
那只手很执着，
it took a lot of effort to restrain the thing and stop it from choking her.
她费了很大的劲才抑制住它，防止它让自己窒息。
Her case was one of the first recorded instances of alien hand syndrome,
她的病例是异己手综合症的最早记录之一，
an extremely rare condition where patients seem to lose all control of one of their limbs,
异手症是一种非常罕见的病情，病人似乎失去了对肢体的全部控制，
usually a hand, hence the name.
通常是手出现问题，因此得名。
And as creepy as that sounds, it can tell us a lot about how our brains control our actions.
它听起来很恐怖，但能告诉我们很多关于大脑如何控制行为的信息。
Now, if you're sitting there worried that your hand is suddenly going to turn on you, you can relax.
现在，如果你坐在那里担心你的手突然攻击自己，放松！
Not all alien hands suddenly turn into assassins...
不是所有的异手都会突然变成刺客...
although it's not uncommon for them to misbehave.
尽管它们的失礼表现屡见不鲜。
Some have casually undressed people, or poured freshly made coffee on the floor.
有些异手会随意脱人衣服，或者把刚煮好的咖啡倒在地板上。
Which, to be fair, is also not great,
公平地说，这种举动并不好，
and kind of makes the syndrome sound like something someone made up to excuse their behavior.
会让异手症听起来有点儿像人们编造出来让人原谅的借口。
But it isn't made up.
但它不是凭空捏造的。
It's a real syndrome, with a known physiological cause.
它是一种真正的综合症，有已知的生理原因。
Even though alien hand syndrome was first reported around 1908,
即使1908年左右首次报道了异手症，
the frequency of cases increased somewhat from the 1940s onwards,
但病例频繁增加是在二十世纪四十年代、
when neurosurgery for epilepsy began to take off.
癫痫神经外科手术开始成功的时候。
That's because the accepted surgical plan at the time involved cutting along the corpus callosum,
这是因为当时公认的手术方案是沿着胼胝体切割，
the bundle of nerves that connects the left and right hemispheres of the brain and lets them talk to each other.
胼胝体是连接大脑左右半球并让它们互相交流的神经束。
Neurosurgeons of the period quickly came to realize, however,
然而，这一时期的神经外科医生很快意识
that a remission in seizures wasn't the only result.
癫痫发作的缓解并不是唯一结果，
There were some... less welcome side effects.
它还有一些不受欢迎的副作用。
Like patients whose left and right hands would face off against each other while they were trying to do stuff.
比如，病人的左右手在试图做事情时相互对抗。
Later in the 1950s, doctors began to notice that
后来在20世纪50年代，医生开始注意到
patients with damage to parts of their frontal lobe showed similar symptoms,
部分大脑额叶损伤的病人也有类似症状。
with their hands reaching out and grasping things without conscious consent.
他们的手没有经过有意识的同意就伸出去抓东西。
These days, alien hand syndrome is more commonly associated with strokes, tumors, and neurodegenerative diseases.
现在，异手症更常与中风、肿瘤和神经退行性疾病联系在一起。
What all these causes have in common is that they can damage three main parts of the brain:
病因的共同之处在于，它们会破坏大脑的三个主要部分：
the medial frontal cortex, the corpus callosum and the parietal lobe.
内侧额叶皮层，胼胝体和顶叶。
Damage in each leads to slightly different variants of the syndrome.
每个部位的损伤都会导致综合症发生轻微不同的变异。
Medial frontal cortex damage usually leads to mischievous dominant hands.
内侧额叶皮层损伤通常导致手不听使唤。
Patients usually find that their right hands grope impulsively,
病人常常发现他们的右手会冲动地摸索，
and seem reluctant to let go of anything they manage to grab.
而且似乎不愿意放弃它们成功抓住的任何东西。
They're also pretty likely to show difficulties with other behaviors that involve the frontal cortex,
它们也很有可能会在其他涉及额叶皮层的行为中表现困难，
like speaking a language they aren't fluent in.
比如不能流利地说一种语言。
With damage to the corpus callosum, like from brain surgery, strokes, and tumors,
比如因为脑外科手术、中风和肿瘤导致的胼胝体受损，
the left hand is usually the one that goes rogue.
会使左手常常随心所欲。
Those patients are also more likely to see their hands literally fight with each other,
病人更有可能看到他们的手相互打架，
what doctors call diagnostic dyspraxia.
也就是医生所说的诊断性运动障碍。
The left hand also tends to go rogue when the damage is in the parietal lobe.
顶叶受损时，左手也倾向于随心所欲。
But unlike the other two, patients with this variant are said to
但与其他两个不同的是，有这种病症变体的病人
feel a quote, 'strong sense of estrangement' from the limb.
会感受到与四肢“强烈的疏远感”。
It's not just that they can't control it,
这不仅仅是他们无法控制它，
it's like someone else's arm is glued onto their body.
更像是其他人的手臂粘在了他们身上。
Some people even name their alien hands, personifying them as someone else.
有些人甚至称它们为异手，把它们拟化成了别人。
The parietal lobe is often involved in body awareness,
顶叶通常与身体意识有关，
so it kinda makes sense that damage to it might prevent you from feeling ownership over a part of your body.
所以，它的受损可能会让你失去对身体的一部分所有权。
Even though doctors have enough data to categorize these three types of alien hand syndrome,
尽管医生有足够多的数据对三种类型的异手症进行分类，
they still aren't sure exactly how the brain damage causes the syndrome.
但对大脑损伤导致异手症的方式仍不能十分肯定。
Most agree that injuries to these areas somehow keep people from being able to inhibit their actions.
大多数人认为，这些区域受损使人无法抑制自己的行为。
If you look at a cup with a handle,
如果你看到一个有把手的杯子，
part of your brain knows you can pick it up, even if you don't consciously think about it.
即使你没有有意识地去思考，但大脑的部分区域却知道你可以把它捡起来。
But, if you see any old cup during the course of your day,
但是，如果你一天中看到任何旧杯子，
you don't just reach out and grab it.
就不只是伸手去拿它。
The kinds of damage associated with an alien hand seem to break down that barrier
与异手相关的伤害似乎打破了
between 'I could do this action' and 'I will do this action' for one limb.
“我可以做这个动作”和“我会做这个动作”之间的障碍。
So the person's hand just goes ahead and grabs the cup, with or without their consent.
所以不管有没有他们的同意，手都会直接伸出去抓住杯子。
And having your hand do something you don't actually want it to do makes it feel...well, alien.
你的手做一些你并不真正想做的事感觉...嗯，很陌生。
Unfortunately, there's no known cure for alien hand syndrome,
不幸的是，目前还没有治疗异手症的方法，
partly because cases are so rare.
部分原因是病例非常罕见。
There are some clever ways patients manage their condition, though.
不过，有一些聪明的方法可以帮助病人控制病情。
Some find it helpful to give their alien hands a cane to keep them occupied.
有些人发现，给他们的异手一根拐杖，让他们保持忙碌很有帮助。
By letting them hold and play with something,
让它们拿着东西玩，
they're distracted from acting on other objects in the environment and cause less trouble.
它们的注意力就不会集中在周围的其他物体上，能减少麻烦。
Others have tried more direct, physical interventions.
其他人尝试了更直接的身体干预。
One case report suggested that symptoms improved after injecting botulinum toxin,
一份病例报告显示注射肉毒杆菌毒素后症状有所改善，
better known as botox, into the affected arm to weaken it.
肉毒杆菌毒素也叫肉毒杆菌，它进入受影响的手臂来削弱病症。
But even if alien hands aren't easy to treat, every case is a learning opportunity,
即使异手症不容易治疗，但每个病例都是一个学习机会，
because doctors can examine how different types of brain damage lead to different behaviors and feelings.
因为医生可以检查不同类型的脑损伤是如何导致不同行为和感觉的。
And the more we learn about how the different parts of our brains work together
我们越了解大脑的不同区域如何协调合作，
to coordinate actions and take ownership of our movements,
掌控我们的行为，
the closer we'll get to finding a real cure someday.
距找到真正的治疗方法就越近。
So next time you accidentally spill coffee down your shirt…
因此你下次不小心把咖啡洒到衬衫上时，
just be glad that your hand is listening to you at all.
就该高兴你的手还在听你指挥。
Thanks for watching this episode of SciShow Psych.
感谢您收看本期的心理科学秀！
If you were intrigued by the idea of your hand becoming not your own,
如果你被手不是自己的想法吸引，
you might like our episode on the opposite effect,
你可能会喜欢我们这一集的反面效果，
how scientists can make you think a hand that isn't yours actually is.
科学家怎么能让你觉得手不是你的呢?
