Language in the brain

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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 isnt 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 1.55.0 mm thick!
• Its area is about 830 cm2, too big to fit into
  your head unless its crumpled up

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Two hemispheres
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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 hemisphereis 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 doesnt

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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 (??) 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 cant 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

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Are there language organs?

• Almost 150 years ago, French doctor Broca said he
  found one Brocas area
• A little later, German doctor Wernicke said he
  found one too Wernickes area
• The modern view is that both areas are crucial to
  language, but have different jobs

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Brocas and Wernickes areas
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Brocas handles grammar?

• Maybe, since damage there does this
• Describe this picture

Cookie jar ... fall over ... chair ... water ...
empty.
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Wernickes handles meaning?

• Maybe, since damage there does this
• Describe this picture

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A processing modelfor reading aloud
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But brain imaging makes the picture more complex
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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 brains 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
• Brocas area and Wernickes area have different
  functions
• New evidence (especially from brain imaging) has
  made the notion of language organs less clear
  than it once was