Brain and Language

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Brain and Language
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• If the human mind was simple enough to
  understand, we'd be too simple to understand
  it.  - Emerson Pugh (retired IBM scientist,
  author)

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Some fun background

• Main Entry sinister Function
  adjectiveEtymology Middle English sinistre,
  from Latin sinistr-, sinister on the left side,
  unlucky, inauspicious
• Left side associations?
• Right side associations?
• http//www.bodymap.com/newsface.html

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Crisscrossed (contralateral) Control

• If I forget thee, O Jerusalem, let my right hand
  forget her cunning. If I do not remember thee,
  let my tongue cleave to the roof of my mouth
  (Psalm 1375-6)
• Left hemisphere (language) right side of body /
  perceptual space
• Right hemisphere left side of body / perceptual
  space
• - everything is crossed except for smell!

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(No Transcript)
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Language on the Left

• Tapping experiments
• shadow speech and tap with each syllable
• easier to tap with left finger than with right
• Dichotic listening
• play different words to each ear
• hear linguistic input better with right ear

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More Language on the Left

• Recognize words better when flashed to right
  visual field than left
• (even in R?L languages)
• Differentiate linguistically significant sounds
  (tones/length) better with right ear
• left ear better at discriminating music (for
  non-musicians)

STAIR ? CHAIR ???? ? ????
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Surgical demonstrations

• Can temporarily paralyze one hemisphere
• (by injecting sodium amytal into the carotoid
  artery)
• Patients with sleeping RH can talk
• Patients with sleeping LH cannot
• During brain surgery, small electric shocks to
  parts of the left hemisphere will silence
  patients mid-sentence

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Hemiplegia and Hemispherectomies

• Hemiplegia
• Paralysis of one side of body due to brain
  lesions
• In children, paralyzed right side predicts
  deficiency in language acquisition
• Hemispherectomy
• Surgical removal of one side of the brain
• Remove LH
• lose most language, keep visual/spatial abilities
• Remove RH
• keep most language, deficiencies vary greatly

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Early Hemispherectomies

• Dennis Whitaker (1976)
• 3 hemispherectomy patients (all younger than 5
  mo.)
• studied when 9 10 y.o.
• LH removed couldnt distinguish between
  grammaticality of sentences
• I paid money by the nun
• I was paid money to the lady
• I was paid money by the boy

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Separating the two hemispheres

• Commisurotomy severing the corpus callosum for
  severe, incurable epilepsy
• IQs tests left hemisphere alone usually tests as
  intelligent as both hemispheres before the
  operation
• Left visual field disconnected from language
  center
• ?
• CLAP ? LAUGH
• (left half of their world has been disconnected
  from their language center)

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Right hemisphere and language

• Word semantics (Beeman 1998)
• Processing relatedness of words, predicting
  meaning
• Activates less-likely meanings of words weakly
• Understanding discourse, speakers intention
• Interpreting narrative script, making inferences
• Metaphor (Brownell 1988)
• More blood flow to the right hemisphere when
  asked to judge metaphor plausibility The
  inventors were squirrels collecting nuts
• Compensates for left hemisphere damage (esp. with
  children)
• Smith and Sugar (1975) removed a boys left
  hemisphere at 5 years, 6 months. As an adult,
  normal language and intellectual capacities

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Handedness and lateralization
Left Hemisphere

• 90 of population 1 or 2 copies of dominant gene
  causing strong Right-hand bias
• Lefties comprise about 9 of the worldwide
  population
• 19 language primarily in the right hemisphere
• (The corpus callosum for left-handers and
  ambidextrous people is 11 larger)

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When do we lateralize?

• Lateralization not present at birth?
• or is the brain just plastic?
• Children with brain damage before 2 y.o., damage
  to RH disrupts speech as much as damage to LH
• Children with brain damage between 2-10, more
  speech disturbance when LH damaged

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The anatomy of the brain

• 4 lobes
• Frontal
• Parietal
• Occipital
• Temporal
• Sylvian Fissure Separates the Frontal and
  Parietal lobes from the Temporal lobe

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Major Language Areas
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Frontal Lobe

• Brocas area responsible for grammar?, inferior
  frontal gyrus of left hemisphere
• Motor area on perimeter of the parietal lobe,
  specific regions dedicated to the motor abilities
  of specific body parts
• Supplementary motor area programs motor
  sequences
• Prefrontal area highest level of brain
  function, intellect, will, emotions thought
  during speech
• Anterior Cingulate Gyrus concentration (in the
  limbic system)

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Motor Area
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Temporal Lobe

• Primary Auditory Area
• Contralateral, in the Sylvian fissure
• Receives auditory information first
• Auditory Association Area
• Superior temporal gyrus, (upper third of temporal
  lobe)
• site of high-level functions that process
  information such as language and music
• Wernickes Area
• lesions make patients unable to understand speech
  (debatable claim)
• Wernickes aphasics usually unaware that they
  have language difficulties
• Auditory Visual Association Area
• posterior part of inferior temporal gyrus
• lots of fiber communication with visual
  communication field
• Involved in visual language processing and lip
  reading

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Parietal and Occipital Lobes

• Parietal Lobe
• Parietal Association Area
• communication fibers from all lobes densely
  connected
• general somaesthetic sensing (feeling in arms,
  face, legs)
• visual and auditory senses also associated
• Occipital Lobe
• Primary Visual Area
• very rear part of the brain (striate area around
  calcarine fissure)
• visual information first enters this area and
  then is processed further by visual association
  area
• Visual Association Area
• around primary visual area, recognizes shape,
  color, movements

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REVIEW
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Is language due to brain size?

• No!
• The average human adult brain weighs about 3 lbs,
  which is nothing compared to an elephants brain
• Not due to high brain mass body mass ratio
• The brain mass body mass ratio is the same for
• a 13-year-old boy
• a 3-year-old chimpanzee

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Is language in one area?

• Noin fact, pinning down the area of the brain
  thats specialized for language is very
  difficult!
• Researchers thought theyd found the language
  center
• planum temporale (the horizontal part of the
  Sylvian Fissure)
• Differences in the lengths of this region
  correspond to the development of the different
  hemispheres
• Deacon (1968) examined 100 human brains and found
  that 68 had enlarged planum temporale on the left
  side, so determined that hed found the control
  center for language
• also seems to be an area largely responsible for
  language processing and production, since this is
  where the auditory association cortex receives
  signals from the ear, which are processed and
  sent to other parts of the brain
• But Gannon and colleagues (1998) were examining
  chimp brains looking for asymmetries, and they
  found that 17 out of 18 chimp brains had enlarged
  plana temporale on left side!
• So chimps are more specialized for language than
  humans?