Lecture 18 - Language and the Brain

Question 1

Describe the location of language representation and processing

Answer 1

• Cerebral cortex
  
  • Broca’s area
  • Wernicke’s area

Question 2

Describe lateralisation in the brain

Answer 2

• Not all features of language are represented in a single hemisphere
• An individual with only one of the hemispheres retains some language ability
• Left hemisphere
  
  • Mechanosensation & movement of right side of body
  • Analytic tasks (eg maths)
  • Most right handers have left lateralisation for language
• Right hemisphere
  
  • Mechanosensation & movement of right side of body
  • Appreciation of complex patterns
    
    • Facial recognition
    • Music and melody
    • Spatial tasks

Question 3

How is language and the brain studied?

Answer 3

• Autopsy studies
  
  • Individuals with neurological problems had their condition carefully described
  • When they passed away, the area of lesion was able to be determined
  • eg Broca’s area
• Imaging of the living brain
  
  • CAT
    
    • Static
    • Good for lesions and tumours
  • PET
    
    • Dynamic
    • Injection of radioactive material and Gamma ray directed to detect area where the most radioactivity is
    • Areas that are being most used have increased blood flow, and thus increased radioactivity is detected in these areas
  • fMRI
    
    • Now the dominant technique: no radiation exposure
    • Also measures haemodynamic response
• Dichotic listening
  
  • If there is left lateralisation for language, than there should be a right ear advantage
  • Right ear: advantage for words, numbers & morse code
  • Left ear: advantgaes for melodies and environmental sounds
• Split brain studies
  
  • Corpus collosum has been severed in cases of severe epilepsy
  • Objects held in one hand behind a screen
    
    • If held in right hand, the object can be named, but in the left, cannot
• ‘Wild children’
  
  • Children who did not receive language input during the critical period
  • eg Genie
    
    • Found at age 14
    • Managed to acquire a large vocabulary, but morphology and syntax never developed

Question 4

What are aphasias?

Describe the major forms

Answer 4

• Acquired disorders of language
• Most commonly due to cerebrovascular accident
• The unique presentation of the aphasia depends on the timing, location and the extent of the damage
• Two main types:
  
  • Non-fluent aphasia
    
    • Damage to area rostral to central sulcus
    • Global aphasia: person can not speak
    • Broca’s aphasia: less severe form
      
      • Effortful, halting speech
      • Telegraphic speech; omission of function words (it, to, at etc.)
  • Fluent aphasia
    
    • Damage to cerebral cortex caudal to central sulcus
    • Most important type is Wernicke’s
      
      • Speech sounds fluent, no halting
      • Sentence intonation normal
      • Speech typically does not make sense

Question 5

Describe phonological dyslexia

Answer 5

• Acquired disorder
• Individual only able to read and pronounce words that have been seen before
  
  • and are thus recognised as a whole
• Cannot pronounce new forms such as blug

Question 6

Describe surface dyslexia

Answer 6

• Acquired disorder where words can not be recognised as wholes
• Words pronounced as sum of individual sounds
  
  • eg yacht → yatcht