So let’s talk about brains. We all know they’re delicious… I mean, important.
They’re crucial for how we handle life in general, from our heartbeats to our feelings
to our walking around. And language is no exception – without a working brain, there’d
be no talking, no listening, no meaning. Or none we could detect, anyway. It’d be an
apocalyptic wasteland of blankness. So three cheers for brains! I’m Moti Lieberman, and
this is The Ling Space.
So our brains run our language operating systems. No big surprise there. But are there specific
parts responsible for all our brilliant conversations? Or is it a whole brain job?
Some early neurologists took a holistic view: they thought any part of your brain was
as good as any other bit for any task you could put your mind to. But as of the late
1800s, the opposing view, known as modularity, took hold. Modularity says that different
parts of the brain have different responsibilities. You can’t usually just swap one part of
your brain around for another without paying a price.
Some of the research that helped modularity win out came from studying language. Particularly,
it was from studying people who had lost part of their linguistic ability, which is a topic
we’ll be covering in the future. For now, let’s look at the two super tasty parts
of the brain that co-chair the language committee. The first, Broca’s area, is in the left
frontal lobe of the brain, around here. That part takes care of the deeper workings of
language: how to put good grammatical sentences together, and how to decode the logical meanings
of the phrases and sentences that are flying our way. It also helps with moving our bodies the right
way to talk. Broca’s area is where all the gears and cranks of our language sit.
The other part is called Wernicke’s area, and it’s here, in the left temporal lobe
of your brain, just above your ear. Wernicke’s area is the hyperactive librarian of language,
in charge of the vast storage of your mental dictionary. It takes care of quickly working
out what those words were that you just encountered and quickly matching up those sounds or visuals to yout
mental meanings. It then ships them off to Broca’s area for processing into sentences.
Wernicke’s area is also where you start when you want to get to talking! It’s the
region where you work out which sounds are the right ones for the words you want to say,
before you ship them off to Broca’s area for arranging and pronouncing. Wernicke’s
area works on comprehension and meaning, whereas Broca’s area holds sway over linguistic
structure and the logic of language.
So like you might guess, these two parts have to communicate with each other all the time
to keep your conversation sliding smoothly along. Broca’s area and Wernicke’s area
are best friends, and they chat with each other all day long. That’s why there’s
a big thick bundle of nerve fibers that hook the two up. This part of our neural network
is way more developed than it is in other primates, which is part of how we’re so
specialized for language. It’s not just the areas themselves that we need for our
crazy fast speaking and comprehension ability, it’s also the connections between them.
But by now you may be thinking, how do we know all this about how the brain processes
language? It’s not like we can pry people’s heads open and look around in there to see what’s going on
when people are interpreting language. Even a zombie wouldn’t expect that to work. Fortunately,
we’ve got a number of different methods that allow us to see what’s going on inside of
those skulls without actually having to open them up and look inside,and we’ll talk about two of them now.
The first of these is functional magnetic resonance imaging, or fMRI. Now, you might have
heard of MRIs; we use them for all kinds of medical diagnoses. But we can also use them
to look at the brain’s responses to different sorts of information. Here’s how it works:
first, we take a scan of your own personal brain. Everyone’s brain is shaped a little
bit differently, so if we don’t know all the all the nooks and crannies of yours, we don't know
how to interpret any of the patterns we measure off you. Can the fMRI scan be of a side shot
of the brain, or does it have to be the classic top view?
After that, the next thing we do is to give you some kind of language stimulus. Maybe you hear
a sentence, or a word, or you see a series of pictures and you need to think about how you would describe
them. But one way or another, we make you engage all that delicious neural apparatus.
And then, we spin up the MRI, and we see what part of your brain lights up - when you want
to make a passive sentence, or you hear the word Halloween, or whatever your task is.
Now, we’re not directly measuring what the brain is doing when we do an fMRI. We can’t get
an image of how the action itself happens – it’s too fast for the machine to get
a continuous reading. What we see instead is what part of the brain is getting blood
that’s extra rich in oxygen. We figure that if a region needs to replenish its energy
by sucking up extra oxygen, that it must just have been doing a lot of work. So it must
be responsible for whatever thing we were trying to test.
But that also means that fMRI can’t really tell us much about exactly what happens over
the course of processing language, or what order it happens in. It just takes a picture of what the
brain looks like after. Now, they’re really, really good pictures – we can get a lot
of detail about where in the brain something is happening - but it doesn’t give
us any idea about time.
For that, we want to use a different technique – electroencephalograms, or EEGs. Our brains
– well, non-zombie brains – are constantly buzzing masses of electrical signals. The
sum of that electricity might not be huge, but it’s enough that we can read through
the skull if we have an electrode cap to stick on you. But because brains are just whirring
and sparking all the time, we need to know that whatever’s going on when we’re
testing you is actually related to language, and not, like, you wondering about what you’re gonna
make for dinner. So we carefully match the brain patterns against the time you hear each word
or syllable in the experiment. Then, we see what changes when you’re listening or interpreting.
EEGs are continuous – we just keep looking with scientific delight at what your brain is doing
until the experiment is over. And because of that, it’s really good at telling
us the order we process language in, and so it can let us know, say, that semantic processing
looks like it happens before just pure syntax. We’ve picked up a lot
of different signals, which we’ll talk about in the future. But we’ve learned a lot about
what happens when from EEGs. On the other hand, though, they’re a lot fuzzier on the
location of where all those things are happening. You can get a general idea, usually,
but it's nothing like those clear, crisp, pretty pictures you get from fMRIs.
So, everything’s got its plusses and minuses.
Except for brains. Figuring out how brains work is even more delicious than the brains
themselves. They’re so awesome! And ours are really good at language – they
have regions dedicated just to that. And we’ve only had these testing techniques operational
for a few decades. We’ve got a lot of discoveries to come. Just the idea of all those neural
developments… it gets me drooling.
So we’ve reached the end of the Ling Space for this week, but if your brain devoured
all my sentences, you learned that we have specific regions in our brain dedicated to
processing and understanding language; that we have multiple methods of measuring that
activity so we can learn how we process our language; that fMRIs take pretty pictures of where brain activity is,
but don’t really tell us when that activity’s happening; and that EEGs are better at telling
us when things happen, but aren’t so great at telling us where.
The Ling Space is written and produced by me, Moti Lieberman. It’s directed by Adèle-Elise
Prévost, our production assistant is Georges Coulombe, our music and sound design is by
Shane Turner, and our graphics team is atelierMUSE. We’re down in the comments below, or you
can bring the discussion back over to our website, where we have some extra material on this
topic. Check us out on Tumblr, Twitter, and Facebook, and if you want to keep expanding
your own personal Ling Space, please subscribe. And we’ll see you next Wednesday. Gaaaaahhhhh