Aphasia

 
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Hi. In this video, we're going to look
into the brain, into your brain. We're going to see where
language is in your brain. And we are going to look
into what can go wrong. Sometimes if something goes
wrong with your brain. Something also goes wrong
with your language. And I'll show you some videos of that. But first, let's look into the different parts of the
brain which seem to be used for language. We have a small brain here. A small model of the brain, where I
can show you those different parts. They're usually located on
the left hemisphere of the brain. One area is this one. It's called Wernicke's area
after a 19th century doctor, medical doctor who discovered its use for
language. Also this area here has a name after
a 19th century doctor, Paul Broca. It's called Broca's area. It's also used for language in some way. The pathway between the two also
seems to be important for language. It's not named after a doctor. It's named the Arcuate fasciculus
with a fancy Latin name. But these are the three areas which
are typically mentioned first when it concerns language in the brain. They're not the only areas for
language in the brain. Basically language seems to be distributed
across the brain in many different areas. And inversely these areas here
are not only used for language. We use them for
other brain functions as well. But still,
these are the three most important ones. How do we know? Well, initially we know,
remember that Broca and Wernicke were doctors,
19th century doctors. They had patients who had had a stroke. And after the stroke had suffered from
certain kinds of language problems. They would speak in a strange way, or they wouldn't be able to understand
everything which was said to them. And then after the patients died,
the doctors could open their brains and look into them and try to figure
out where the problems had been. And by correlating the areas in the brain which were
touched and the language problems, they could find out something
about the function of those areas. So if these areas functioned and
it means you don't speak very well, it definitely also means that speaking
well is at least partly in this area here. Those language-related
problems are called aphasia. Or at least, many language-related
problems in the brain fall under the general rubric of aphasia. That means aphasia can be
many different things. And those many different things seem
to be connected in an interesting way to these three areas of Wernicke,
Broca, and the Arcuate fasciculus. The first type of aphasia is
called Wernicke's aphasia, and it's called that because it's
obviously located in Wernicke's area. That's where the physical
problem seems to be. Wernicke's aphasia is also called
fluent aphasia because if you listen to a patient, they sound very fluent. They make very nice grammatical sentences, all the sounds come out of their mouth
fluently like for any other speaker. But if you listen closely what they
say doesn't seem to make any sense. They use made up words, they put words together which
don't really seem to fit together. You cannot make any sense
out of what they say. Their problem seems to be
connecting sound with meaning, connecting the form of
language with meaning. There's nothing wrong with the form, but they just cannot connect
it to the meaning. So if they see some kind of object. If they see my glasses here,
they understand it. They understand what it is, they just
cannot connect it to the sound glasses. They cannot find those sounds. And that in turn means that these people
typically don't just have problems in speaking, they also have
problems understanding. Because inversely,
if I say the word glasses to them, they understand that word. They understand it's a word of English,
but they just cannot connect it with what
it means, with this object here. The second area we looked
at is Broca's area. And interestingly, Broca's aphasia is almost the complete
opposite of Wernicke's aphasia. Broca's aphasia is
sometimes called non-fluent aphasia because these speakers speak,
well, non-fluently. They make ungrammatical sentences,
they have hesitations. They make a lot of mistakes generally,
but what they say does make sense. So if you show your glasses to
a patient with Broca's aphasia, they will know the word glasses. They just will not be able to
make a well-formed sentence. They will not be able to say,
put your glasses on. They will say put glasses, or
glasses put, or something like that. And then with a lot of hesitations. So what seems to be wrong with
Broca's aphasia's patients, it's not that they cannot
connect form with meaning. But there's something in the form itself. There's something broken in their syntax. There's something broken
in their morphology or at least in their inflectional morphology. So things can be wrong with Broca's area. Things can be wrong with Wernicke's area,
but things can also be wrong with the pathway
between those two with Arcuate fasciculus. In that case we say that the patient
suffer from conduction aphasia, which is a bit rarer than the other two. It's rarer, but it also is strange. It's interesting. If you listen to patients at first
really nothing seems to be wrong. They speak fluently,
they speaking grammatical sentences, and what they say seems to make sense,
perfect. But then if you ask them to repeat
words literally or sentences literally, or you ask them to, for instance,
list the numbers between one and ten, all of a sudden they
seem to have a problem. What seems to be wrong with these
patients is something memory related. So they seem to have lost some
of their capacity for memory. From studying aphasia like this,
we can also learn certain things about how healthy brains work and
how they deal with language. For instance if Broca's patients
typically have problems with syntax and morphology that implies
that in the healthy brain, important parts of syntax and morphology
are probably located in Broca's area. And similarly, if you have
a problem in Wernicke's area and that means that you cannot
easily connect form and meaning. That means that in healthy brains, Wernicke's area is probably used for
making exactly that connection. Now obviously, I've been simplifying. There's many more different kinds of
problems than just these three, and they're also sometimes mixed. And typically, if you have a stroke, that stroke
doesn't hit exactly one precise area. It doesn't hit exactly just Broca's or
Wernicke's area. A larger area might be involved, and
in the larger area you might find, for instance, areas used for motor control. And if motor control is hit, it means
you just can't speak very easily for purely physical reasons. Now in the next video, we're going
to look more into brain problems. But we're going to look into
brain problems which you have and which you have every day. Problems in your brain and
in your language.

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