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Brain and Language

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

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Title: Brain and Language


1
Brain and Language
2
  • If the human mind was simple enough to
    understand, we'd be too simple to understand
    it.   - Emerson Pugh (retired IBM scientist,
    author)

3
Some fun background
  • Main Entry sinister Function
    adjective Etymology 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

4
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!

5
(No Transcript)
6
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

7
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 ???? ? ????
8
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

9
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

10
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

11
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)

12
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

13
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)

14
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

15
The anatomy of the brain
  • 4 lobes
  • Frontal
  • Parietal
  • Occipital
  • Temporal
  • Sylvian Fissure Separates the Frontal and
    Parietal lobes from the Temporal lobe

16
Major Language Areas
17
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)

18
Motor Area
19
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

20
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

21
REVIEW
22
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

23
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?
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