In 1861, a patient arrived at a Paris hospital
saying the syllable “Tan” over and over again
His doctor, Paul Broca, found that the man could understand language without a problem;
他只是除了”Tan” 之外 什么都不会说
he just couldn’t say anything — besides “Tan”.
When the patient unexpectedly died a few days later.
Broca dissected his brain and found a small bit of damage
called the lesion on the left frontal lobe . Leaving him
to conclude that this part of the brain must be responsible for speech generation.
Back then, scientists had only recently accepted the idea that
and some kinda mean experiments
with animals had convinced them that
different parts of the brain were dedicated to different mental jobs.
Broca’s lesion method seemed like the way to draw up a localized map of brain activity
in humans: doctors found patients with specific cognitive deficits and then
matched those eficits up with the damaged parts of their brains.
From these patients, they deduced that new memories are formed in the hippocampus, fear
comes from the amygdala, and that we recognize faces using the fusiform face area.
However, there’s a big difference between correlating a certain part of the brain with
a certain mental task and proving that that part of the brain actually does that task.
于是 当90年代我们发明功能磁共振成像机器 并用来追踪脑部即时变化时
And, sure enough, when we developed the fMRI machine in the 1990s, to track moment-to-moment
changes in brain activity, the old localized map of brain activity quickly began to unravel.
一方面 每次脑活动 脑皮层就似乎活动起来
For one thing, huge swaths of the brain seem to activate every time the brain does anything
at all, suggesting that even the most basic mental tasks require a coordinated effort.
And it turns out that this coordination relies on a network of long-range communication fibers.
In fact, damage to these fibers explained why some people with
intact Broca’s areas couldn’t speak.And, the communications network also
explained why some people with broken Broca’s areas could speak
Because the fibers proved able to rewire Broca’s tasks
to other parts of the brain.
But, just because a certain part of the brain lights up during a certain mental task doesn’t
necessarily mean that brain part is doing something critical to that task.
In other words, the MRI method of brain imaging turned out to have the same problem as the
Fortunately, we can get around this problem by putting the two methods together.
Recently, researchers performed scans on 182 people with brain lesions – mostly soldiers
with shrapnel wounds – and had them perform a battery of mental tasks.
Then, they put all the scans together to see
which brain parts were always active when the subjects could perform a task,
and which parts were always turned off when they could not.
As a result, we now have a map of the brain that shows which parts work together to help
如 理解语言 解决疑虑和记忆功能
us do brainy things like understand language, solve puzzles, and remember stuff.
But even with these maps, our own brains still give us a lot to ponder.
We may never, for example, why Broca’s patient could only say “Tan,” or whether there was
something else he was trying to tell us.
This video was sponsored by Audible.com, the leading provider of audiobooks, including
Oliver Sacks’ 《The Man Who Mistook His Wife For a Hat》 a fascinating collection
of curious neurological cases like this one:
For not only did Dr P. increasingly fail to see faces
but he saw faces when there were no faces to see
genially, Magoo-like, when in the street he might pat
the heads of water hydrants and parking meters,
taking these to be the heads of children
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