[♪ INTRO ]
电视上 或是小说中 昏迷的病人通常被描述成一种状态:像睡着了一样
On TV, or in novels, patients in comas areusually described the same way: like they’re sleeping.
On the outside, that makes sense.
After all, they ’ ll have the
same closed eyes and maybe even slower breathing or a
But while a sleeping person and a coma
patient might look the same on the outside, on the
但内里 尤其是他们的大脑中 是相当不同的
inside — especially inside their heads — they’revery different.
For the brain, being in a coma is almost nothing like being asleep.
It’s actually more like being under generalanesthesia.
但是 大脑中发生了什么 非常有趣
But what’s happening in there is prettyfascinating.
Comas are what clinicians call disorders ofconsciousness.
There are a few of them,
比如昏迷 植物状态 都是由
including comas and vegetative states, and they ’ re caused by
some sort of damage to the brain.
This could come from something like a stroke,
oxygen deprivation, or a major hit to the head,
like in a car accident.
The specific mechanism that causes these disorders is still up
for debate, but regardless, some
damage triggers a deep unconsciousness that can last for days or months.
On a philosophical level, what it means to be conscious is debatable.
但从医学上来说 醒着的人都有两种特征 清醒且有意识
But medically speaking, a conscious personis generally two things: awake and aware.
Being awake is pretty simple:
It ’ s having the reflexes to do things like open your eyes.
Being aware means
that you can respond to something happening around you — like by
squeezing someone’s hand if they ask,
or holding up a certain number of fingers.
When someone has a disorder of consciousness,
one or both of these things is disrupted.
And with comas, it’s both.
A coma patient will have some basic,
automatic responses that show their brain is somewhat
functional — like pupil dilation — but they
won ’ t open their eyes if someone pokes them,
And they can’t respond to what’s goingon around them. Now,
even though that might sound like you
after your last all-night study session, comas
are nothing like being in a heavy sleep.
For one, the brain is using a lot less energy
during a coma — about 10 to 20 % less than
even the deepest part of sleep,
and 50 to 60 % less than when you ’ re awake.
This is a sign of significantly lowered activity all
across the brain, and it plays out in
a few ways.
One is that the comatose brain doesn ’ t go
through the regular cycles of sleep. Normally,
brain goes through periods of rapid eye movement, or REM sleep.
During these times,
your brain is actually generating electrical activity at a similar
level that it does when it’s awake.
But the comatose brain doesn ’ t produce those high levels
of activity, so, as far as we
can tell from brain scans, it doesn’t gothrough REM cycles.
Since REM is the phase of sleep associated with vivid dreams,
所以 这也意味着 昏迷的病人
this also means that coma
patients probably don ’ t dream,
同样 尽管很多人汇报说 他们没有昏迷
either — although many have reported them on their way out of a coma.
Probably the biggest difference between comas and other conditions, though,
is the activity
in the brain ’ s cerebral cortex —
or what we tend to think of as the main part of the brain
During a coma, there ’ s activation in some basic,
sensory areas, but they ’ re not being
So the brain can ’ t actually make sense
of what those sensory signals mean.
举个例子 2000年 Brain期刊上的一项研究
For example, a study done in the journal Brain
in 2000 showed that five patients in vegetative
states and comas had some activity in their auditory cortex in response to sound.
But those signals weren ’ t sent on to a place
in the brain where they could be understood. So,
you might ’ ve heard that someone in a coma can understand you,
even if they can ’ t
respond — but that’s not totally true.
They can technically hear you, but according to most research,
they won ’ t be able to
process anything you say.
It ’ s different than what happens when you, say,
fall asleep during lecture.
According to studies, the sleeping brain can process what it hears,
even if you don ’ t
realize or remember it.
This lack of processing happens because, during a coma,
two major networks in the cortex are disrupted:
one that covers internal awareness, and one that does external awareness.
Internal awareness deals with things like talking inside your head and wandering thoughts.
External awareness is more about how you process external stimuli,
like what my face looks like
These networks can get interrupted in other disorders,
too — like locked-in syndrome,
where someone is conscious but can’t movenormally.
But in that case, only one network is disrupted.
With comas, it ’ s both,
so there ’ s not a ton of higher-level processing happening.
In general, the comatose brain is a lot more disconnected
from the things happening around
it than in some other conditions or when you’reasleep.
If anything, it’s actually most similarto being under general anesthesia.
Some physicians even call anesthesia a “ reversible coma ”,
and it can be used to study real
comas without putting someone in serious danger. Ultimately,
depending on the severity of the damage,
a coma patient might heal and slowly
come back to regular consciousness, becomingboth awake and aware.
Once they do,
they probably won ’ t have any memory of the experience — even if they
do remember the process of waking up.
Which probably isn’t such a bad thing.
Although doctors work to get patients out of comas
as safely and quickly as possible,
studying them and how they work are reallyimportant.
After all, comas are key ways
for us to understand the root of consciousness in our brains.
By untangling the things that are happening
inside our heads when we lose connection with
the world, we ’ re able to get a better idea
of the biology that links us to reality in the first place.
And that’s definitely worth understanding.
Thanks for watching this episode of SciShowPsych!
If you ’ d like to keep exploring the human mind with us,
you can go to youtube.com/scishowpsych and subscribe.
[♪ OUTRO ]