10 Language

1
10 Language
2
Introduction

• Language
• System by which sounds, symbols, and gestures
  used for communication
• Process
• Language comes into brain through visual and
  auditory systems
• Motor system Produces speech, writing
• Processing between sensory and motor systems

3
Specialized Language Areas

• Aphasia
• Partial/complete loss of language abilities
  following brain damage
• Latin Lingua Thought the tongue controlled
  language
• 1770 Johann Gesner aphasia is a form of brain
  damage disconnecting ideas from words
• 1825 Jean-Baptist Bouillard speech is
  controlled by frontal lobes
• 1861 Paul Brocca Cortical area in left frontal
  lobe

4
Specialized Language Areas

• Wada procedure Anesthetize single hemisphere
  (sodium amytal in left carotid artery)
• Left Hemisphere dominance
• Brocas areaPaul Broca in 1864 Region of
  dominant left frontal lobe Articulate speech,
  speech production
• Wernickes area
• Karl Wernicke in 1874 Superior surface of
• temporal lobe between auditory cortex and
• angular gyrus Lesions disrupt normal
• speech but more so comprehension

5
Specialized Language Areas

• Brocas Aphasia (motor, nonfluent aphasia)
• Difficulty speaking, but understand spoken/heard
  language
• Paraphasic errors
• Pause to search for words, repeat overlearned
  things, difficulty repeating words

6
Specialized Language Areas

• Wernickes aphasia
• Speech fluent, comprehension poor
• Strange mixture of clarity and gibberish
• undisturbed by sound of own or others speech
• Correct sounds, incorrect sequence
• Incorrect word similar to correct word
• Comprehension difficult to assess
• Playing music, writing similar

7
Specialized Language Areas

1. Brocas area
2. Wernickes area
3. Arcuate Fasciculus
4. Angular gyrus

Wernicke-Geschwind Model
8
Specialized Language Areas

1. Brocas area
2. Wernickes area
3. Arcuate Fasciculus
4. Angular gyrus

9
Specialized Language Areas

• Conduction Aphasia
• Lesion of fibers composing arcuate fasciculus
• Comparison with Brocas aphasia, Wernickes
  aphasia Comprehension good, speech fluent
• Difficulty repeating words
• Symptoms Repetition substitutes/omits words,
  paraphasic errors, cannot repeat function,
  nonsense words, polysyllabic words

10
Specialized Language Areas

• Aphasia in Bilinguals and the Deaf
• Aphasia in bilinguals- Language affected depends
  on Order, fluency, use of language
• Sign language aphasias analagous to speech
  aphasias ? but can be produced by lesions in
  slightly different locations
• Verbal and sign language recovered together in
  one case? indicating overlapping regions used for
  both
• Evidence suggests some universality to language
  processing in the brain

11
Asymmetrical Language Processing

• Split-Brain Studies
• Roger Sperry (1950s)
• Split-brain procedure
• Sever axons making up the corpus callosum
• No major deficits
• With proper experiments, animals behaved as if
  they had 2 brains

?
12
Asymmetrical Language Processing

• Split-Brain Humans

13
Asymmetrical Language Processing

• Left Hemisphere Language Dominance
• Right visual field, repeated easily
• Left visual field, difficulty verbalizing
• Image only in left visual field, object in left
  hand, unable to describe
• Split-brain Unable to describe anything to left
  of visual fixation point

14
Asymmetrical Language Processing

• Language Functions of the Right Hemisphere
• Functions of right hemisphere Read and
  understand numbers, letters, and short words
  (nonverbal response)
• Baynes, Gazzaniga, and colleagues Case of
  patient with right hemisphere able to write, but
  not speak
• Right hemisphere Drawing, 3-D puzzles, sound
  nuances
• Prosidy

15
Asymmetrical Language Processing

• Anatomical Asymmetry and Language
• Left lateral (Sylvian) fissure longer and less
  steep than right
• Geschwind and Levitsky Left planum temporal
  larger than right in 65 cases
• Functional human asymmetry More than 90 humans
  right-handed
• Animals Equal numbers of right-handers and
  left-handers, or no dominance

16
Language Brain Stimulation and Brain Imaging

• Old methods Correlate language deficits with
  postmortem analysis of brain damage
• Recent techniques
• Electrical brain stimulation
• Functional Imaging

17
Brain Stimulation

1. Motor cortex Immediate speech arrest
2. Brocas area Speech stopped after strong
   stimulation,
3. speech hesitation from weak stimulation
4. Posterior parietal lobe near Sylvian fissure
   and temporal lobe Word confusion and speech
   arrest
5. Small parts of cortex naming, reading,
   repeating facial movements

18
Brain Stimulation

• N, naming difficulty with intact speech (anomia)
  
• A, arrested speech
• G, grammatical errors
• J, jargon (fluent speech with frequent errors)
• R, failure to read
• M, facial movement errors.

19
Brain Imaging

• fMRIRecord during language tasks
• Activated brain areas consistent with temporal
  and parietal language areas
• More activity than expected in nondominant
  hemisphere

Generate words from a category
Silently repeat a heard sentence
Listen to a story
20
Brain Imaging

• PET
• Compare
• Sensory
• responses to
• words vs.
• Speech
• production

21
Language Acquisition

• Mechanism in infants
• Syllable emphasis
• Motherese
• Adults talk to infants Speech slower,
  exaggerated, vowel sounds clearly articulated
• Complexity Foreign language
• Dehaene-Lambertz 3 month infant, brain response
  to spoken words similar to adults

22
Concluding Remarks

• Language processing
• Person repeats word read
• Initial activity in visual cortex, then activity
  in motor cortex corresponding to muscles that
  move vocal apparatus
• Multiple brain areas critical for language
• Language skills Naming, articulation, grammar
  usage, comprehension
• Further brain imaging studies will reveal more
  about language systems organization

23

• End of Presentation