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Language in the brain
Linguistics lecture #7
November 16, 2006
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Overview
• Meet your brain!
• Left brain, right brain
• Are there “language organs”?
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Parts of the brain
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The cerebral cortex isn’t pudding
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Why is it so wrinkled?
• The cerebral cortex contains billions of
neurons in layered neural networks
• But it is only 1.5~5.0 mm thick!
• Its area is about 830 cm2, too big to fit into
your head unless it’s crumpled up
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Two hemispheres
connection
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The wiring is “backwards”
• Each hemisphere has direct contact mostly
with the opposite side of the body!
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Different talents
• In general, the right hemisphere is better at
processing wholes and spatial information
• In general, the left hemisphere is better at
analyzing into parts and time information
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Which hemisphere
is better at language?
• Language involves analyzing parts related
across time, right?
• And in fact, most people process language
more in the left hemisphere
• But how do scientists know this?
(They knew this long before the invention of
machines and computers that could produce
images of brain activity.)
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Evidence from brain damage
• “Loss” of language caused by brain damage
is called aphasia
• For 150 years, doctors have known that
damage to the left hemisphere can cause
aphasia, but damage to the right hemisphere
mostly doesn’t
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Experimental evidence
• If language is processed better in the left
hemisphere, which word should be easier to
recognize?
DOG
+
CAT
• “CAT”, since its image goes directly to the
left hemisphere
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Split-brain evidence
• To prevent epilepsy (癲癇) from affecting
the whole brain, surgery can be done to cut
the connection between the hemispheres
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Testing split-brain patients
• Show split-brain patients a
picture on the left side
• Results: They can choose
the correct object with their
left hand
• But they can’t tell you the
name of the object
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Brain imaging
• Today the “hottest” way to study language
in the brain is to use special machines that
can create images of brain activity
EEG: measures electrical patterns on surface of
brain (fast and cheap, but “blurry” pictures)
PET: first inject radioactive stuff into the blood,
make images of “glowing” blood flow (risky)
fMRI: use magnets and quantum physics to make
oxygen emit energy, then image blood flow (safe,
pretty fast, pretty clear, but expensive)
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Is your language in the left?
• Brain imaging (and other evidence) shows
that it depends on sex and handedness
(women and lefties are less lefty)
Phonological processing
Female
Male
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Are there “language organs”?
• Almost 150 years ago, French doctor Broca
said he found one: Broca’s area
• A little later, German doctor Wernicke said
he found one too: Wernicke’s area
• The modern view is that both areas are
crucial to language, but have different jobs
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Broca’s and Wernicke’s areas
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Broca’s handles “grammar”?
• Maybe, since damage there does this:
Describe this picture:
“Cookie jar ... fall over ... chair ... water ... empty.”
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Wernicke’s handles “meaning”?
• Maybe, since damage there does this:
Describe this picture:
Well, this is... mother is
away here working her work
out of here to get her better,
but when she's looking, the
two boys looking in the
other part. One their small tile into her time here. She's
working another time because she's getting to. So two boys
work together and one is sneaking around here making his
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work and his further funnas his time he had.
A processing model
for reading aloud
first process
words and
meaning
then process
grammar
including
phonology
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But brain imaging makes the
picture more complex
phonology
in left,
but not all
in Broca’s
meaning
everywhere
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The interactionists are happy!
• “Every new functional imaging study seems
to bring another language area to our
attention.... This all leads to the conclusion
that domains like language do not live
within well-defined borders.…”
Elman, Bates, Johnson, Karmiloff-Smith, Parisi, &
Plunkett (1996). Rethinking innateness: A connectionist
perspective on development. MIT Press.
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The modularists are confused!
• “But to be honest, no one really knows what
either Broca's area or Wernicke's area is for.”
Pinker (1994). The language instinct. William Morrow.
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Summary
• The brain’s “smartest part” is the cerebral
cortex, divided into two hemispheres
• The left hemisphere tends to be better at
processing language, in general…
• Evidence comes from aphasia, split-brain
patients, experiments, and brain imaging
• Broca’s area and Wernicke’s area have
different functions
• New evidence (especially from brain
imaging) has made the notion of “language
organs” less clear than it once was
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