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看到不存在的东西是怎么回事?

Visual Illusions: Why You See Things That Aren't There

你记得卡通人物撞到了头然后
So, you know when cartoon characters bump their head and then there’s, like, stars
好像有许多星星在绕着他们转的样子吗
start whirling around them?
这存在一定的事实依据 如果你十分用力撞击你的脑袋
Well, there’s actually some truth to that: if you bump your head hard enough, you might
你可能会看到许多闪烁的小光斑
actually see little flickering lights in your eyes.
这些光斑是内视现象的一种表现
These flickers are an example of what’s known as an entoptic phenomenon, where your
你的大脑曲解了传来的信号 所以你会看到一些事实上并不存在的东西
brain misinterprets signals so you see things that aren’t really there.
它和真性幻觉并不相同 但它确实混淆了
It’s not quite the same as a full-blown hallucination, but it is messing with your
对现实的感知
perception of reality.
回溯到17世纪60年代 艾萨克 牛顿为了体验这一现象 他把一个巨大的金属别针粘在
Back in the 1660s, Isaac Newton experimented with this by STICKING A GIANT METAL PIN INTO
自己的眼窝处 以便于按压到眼球的背部
HIS EYE SOCKET TO PRESS ON THE BACK OF HIS EYE.
艾萨克 牛顿吗 为什么呢
Why, Isaac Newton?
你不是一个聪明的家伙吗
You’re supposed to be a smart guy!
好消息就是你不必把东西粘在眼睛里
The good news is, you don’t need to stick things in your eye to experience entoptic
来体验内视现象
phenomena.
你也不应这么做
And also you shouldn’t.
你可以通过揉眼睛来看到相似的光斑 或者仅仅长时间盯着
You can see similar flickers by rubbing your eyes, or even staring at something boring
一些无聊的东西看 也可能看到这种光斑
for too long.
这一切都是由于眼睛和大脑里一些巧妙的设置
And all because of some quirks in your eyes and brain.
例如 无论房间里多么暗 你也永远不会觉得它
For example, no matter how dark it is in a room, you’ll never see it as 100% completely,
百分百、彻彻底底是黑暗的
totally black.
这是因为你视网膜中负责检测光线的视杆细胞非常敏感
That’s because the rod cells in your retina, which detect light, are really sensitive.
事实上 我们已经知道 视杆细胞可以对可见光的每个单光子都产生反应
In fact, the rods have been known to respond to just a single photon of visible light.
它们依靠一种叫作视网膜紫质的蛋白进行工作
They work using a protein called rhodopsin.
在每个视杆细胞中都有许多视紫质 当光线划过
There’s lots of rhodopsin in each rod cell, and when light hits rhodopsin, it changes
视紫质就会发生异构作用 改变形体
form, in a process called isomerization.
这种改变会使神经节细胞向你的大脑发送一个信号
The change causes a special cell called a ganglion cell to send a signal to your brain,
大脑会把这些信号转化为图像
which processes the signal into an image.
但其他形式的能量也会使视紫质发生变形 比如说热量
But other types of energy can cause rhodopsin to change form, too — like thermal energy.
所以你的眼睛也可以对热量做出反应
So your eyes can respond to heat instead of light!
对于单个的视紫质蛋白来说这种反应不太常发生
It’s pretty rare for an individual rhodopsin protein to react this way, but there’s so
但是在一个视杆细胞中有如此多蛋白以致于平均每个细胞每两分钟
much of the stuff in a single rod cell that the average cell will mistakenly send a electrical
就会向大脑发送一个错误的电信号
signal to the brain once every couple of minutes.
又由于在视网膜中有超过一百万个视杆细胞
And because there are over a hundred million rods in your retina, that translates to a
就相当于几乎每时每刻都在向大脑传送大量杂乱无序的信号
lot of random signals coming in pretty much all the time.
所以即使环境完全黑暗 在房间中没有一个可见的光子
So even if it is totally dark, without a single photon of visible light in the room, thermal
热量也会激活你的视杆细胞 你也就不会看到完全的黑暗
energy will activate your rod cells anyway, and you will not see total darkness.
相反 你会看到一种黑色的明暗层次 它叫做暗光
Instead, you’ll see a very dark shade of grey, called eigengrau.
你可以自己尝试一下
You can try this for yourself by going into a
走进一个完全漆黑的房间里 然后闭上眼睛
totally pitch-black room and closing your eyes.
如果没有光子进入你的眼睛 你将会看到暗光
If there are no photons entering your eye, you’ll see eigengrau.
但你不能因此将所有的内视现象都归咎于视杆细胞
But you can’t blame your rods for all entoptic phenomena.
有时神经节细胞即使没有被视杆细胞激活
Sometimes, the ganglion cells fire a signal even when they’re
也会发出电信号
not excited by the rod cells.
原来压力也会激活神经节细胞
It turns out that pressure can also excite ganglion cells.
所以如果你用一点力仔细揉眼睛
So if you carefully rub your eyes and apply a little bit of pressure, you’ll cause ganglion
神经节细胞也会像有光线进入眼睛那样发出信号
cells to fire signals as if there’s light entering your eyes.
你的大脑会把这些信号转化为一种闪烁的小光斑 这叫做光幻视
Your brain interprets those signals as little flashes of lights called phosphenes.
确切地说是压力性光幻视 因为它们是由你眼睛中压力的变化
Specifically, they’re pressure phosphenes, because they’re caused by a change in pressure
引起的
in your eye.
但是也有其他方法可以看到光幻视
But there are other ways to see phosphenes — like if you’ve ever had your vision
比如当你站起来太快的时候会觉得世界在摇晃
go wonky when you stood up too fast.
视网膜代谢率非常高 这意味着
The retina has an especially high metabolic rate, which means that it needs tons of glucose
它需要大量的葡萄糖和氧气
and oxygen for its size.
当你站得太快了 血压就会突然下降
When you stand up too fast, there’s a sudden drop in blood pressure, and for a few seconds
在几秒的时间内你的视网膜得不到充足的血液 无法正常工作
your retinas might not get enough blood to work properly.
这就导致你的神经节细胞传递出错误的信号
That causes your ganglion cells to misfire random signals,
然后你就看到了这些小点点和小光斑
and you see those little dots and flashes.
那用力击打头部然后看到小星星该怎么解释呢
And if you hit your head really hard and see stars?
这是由于你撞击的太过用力以致于干扰到了枕叶
That’s because you bumped it hard enough to mess with your occipital lobe: the part
枕叶是大脑中处理视觉信息的部分
of your brain that does visual processing.
一些人比其他人更容易出现内视现象
Some people experience entoptic phenomena more than others.
比如犯人和货车司机 由于缺乏视觉刺激
For prisoners and truck drivers, for example, phosphenes can get pretty severe because of
光幻视会格外严重
the lack of visual stimulation.
在有些案例中 光幻视不仅仅是闪烁的光斑
In some cases, they’ll see phosphenes as more than just a flicker: they’ll see glowing
有些人会看到光圈或旋转的曲线 就像你自己看完了整场电影
circles or spinning spirals, in what’s known as a prisoner’s cinema, because it’s kind
所以被称为 囚徒电影院
of like you’re seeing a full cinema show.
囚徒电影院可能是由光幻视和感觉剥夺共同引起的
Prisoner’s cinema is probably caused by a combination of phosphenes and sensory deprivation.
虽然一个囚犯或者货车司机的视野是开阔的 但他们的眼睛基本上一直盯着一个固定的画面
Even though a prisoner’s or truck driver’s eyes are open, they’re staring at what’s
他们的大脑没办法得到新的信息
basically an unchanging scene, so their brain isn’t getting much new information.
而当你的视觉被剥夺之后 你的大脑就会放大来自神经节细胞的信号
And when you’re visually deprived, your brain amplifies the signals coming from your
以弥补视觉刺激的缺失
ganglion cells to make up for the lack of stimulation,
于是你就看到了这些圈圈和螺旋
and you end up seeing those circles or spirals.
所以他们可能不完全具备幻觉的特征 但是你的眼睛和大脑
So they might not be full-on hallucinations, but there are lots of ways that your eyes
有很多种方法来捉弄你
and brain play tricks on you.
你也不需要在眼窝上粘贴一些夸张的物件
And you do not need to stick horrifically large things
来体验它
into your eye socket to experience them!
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Thanks for watching this episode of SciShow, which was brought to you by our patrons on
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click that button!

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视频概述

从别后 忆相逢 几回魂梦与君同_(:з」∠)_

听录译者

收集自网络

翻译译者

王随意

审核员

霜霜

视频来源

https://www.youtube.com/watch?v=ZnRAA0CeSIk

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