lecture 15

Question 1

What are the three categories of aphasia?

Answer 1

Receptive aphasia: the inability to comprehend language
Expressive aphasia: the inability to generate written or spoken language
Global aphasia: combines both receptive and expressive components

Question 2

When does language develop in humans?

Answer 2

(approximate)

• 4 months: babbles many speech sounds
• 10 months: babbling reveals household’s language
• 12 months: one-word stage
• 24 months: two-word, telegraphic speech
• 24+ months: language develops rapidly into complete sentences

Question 3

Which areas of the brain are involved in language?

Answer 3

• Broca’s area: left side, speech production (simplistic)
• primary auditory cortex
• wernicke’s area: can produce speech but can’t interpret language (simplistic)
• primary visual cortex
  (- primary motor cortex
• primary somatic sensory cortex)
• angular gyrus (meaning)

Question 4

What is a non-anatomical approach to defining areas of the brain related to speech?

Answer 4

Written word:

• early visual processing: striate cortex/primary visual cortex
• visual word recognition: extrastriate cortex

Spoken word:

• early auditory processing: primary auditory cortex
• auditory word recognition: temporoparietal cortex (angular gyrus), anterior superior temporal cortex

Both:

• semantic association: inferior frontal cortex
• premotor coding: supplementary motor area, other areas near sylvian fissure
• motor control of speech: primary motor cortex
• speech

Question 5

What are the characteristics of Broca’s and Wernicke’s aphasias?

Answer 5

Broca’s aphasia (expressive):

• halting speech
• tendency to repeat phrases or words (perseveration)
• disordered syntax
• disordered grammar
• disordered structure of individual words
• comprehension intact

Wernicke’s aphasia:

• fluent speech
• little spontaneous repetition
• syntax adequate
• grammar adequate
• contrived or inappropriate words
• comprehension not intact

Question 6

How might conduction aphasia be caused?

Answer 6

• disconnecting Wernicke’s and Broca’s area (arcuate fasciculus)

Question 7

What is alexia? What are its symptoms?

Answer 7

• word blindness
• ability to write a passage but inability to read back the passage
• ability to recognise the individual letters as a letter (N = the letter N, B = the letter B)
• inability to associate individual letters with a sound (N = “enn”, B = “bee”
• inability to read a word as a whole
• damage to inferior temporal region

Question 8

How is language localised?

Answer 8

• penfield’s map of speech affecting areas
• cumulative data (% means % of patients who’s speech was disrupted by stimulation at this point)
• broca’s area - didn’t have 100% more like 18%
• also above broca’s area
• wernicke’s
• other places around

takeaway message:
- speech is not as discretely localised into functional modules as textbooks have wanted to say

Question 9

What is hemispheric asymmetry?

Answer 9

• left and right cerebral hemispheres are noticeably different
• e.g. angle of lateral/sylvian fissure
• temporal lobe on left is ‘meatier’
• planum temporale is noticeably asymmetric: big on the left, single gyrus on the right (where wernicke’s area would be expected)

Question 10

What are the functions of the left and right hemispheres?

Answer 10

Left hemisphere functions:

• analysis of right visual field
• stereognosis (right hand)
• lexical and syntactic language
• writing
• speech

Right hemisphere functions

• analysis of left visual field
• stereognosis (left hand)
• emotional colouring of language
• spatial abilities
• rudimentary speech

Question 11

Do other animals have “generative” language?

Answer 11

• not really, bonobo, our closest relative has some form of a communication, capacity to solve problems etc but they don’t have the ability to generate the rich layers of language that we are

Question 12

What is it that our nervous system has that allows us to create language as we know it?

Answer 12

Is there a Universal Grammar, a deep structure to all human language, and an innate capacity for this to develop in children; a “language instinct”?

Or, is the capacity to acquire language another example of the huge capacity of human brains to classify and represent information to solve complex problems in complex social and physical environments?

• noam chomsky believes that we are born with the capacity to develop language - a commonality
• moved away from this to instead believe that we are just really good at solving problems (e.g Daniel Everett with people in the amazon): inflection and tonality more influential in this Piraha - not conforming to any of the uniform grammar rules proposed by chomsky
• steven pinsky

Question 13

What did a recent study (by Dunn and others show?

Answer 13

• used a “phylogenetic” mapping stochastic modelling approach to refute the universal constraints on language generation
• two word-order features plotted onto maximum clade credibility trees of the four language families
• “cultural evolution is the primary factor that determines linguistic structure, with the current state of a linguistic system shaping and constraining future states.”

Question 14

What is the population founder effect?

Answer 14

• the loss of genetic variation that occurs when a new population is established by a very small number of individuals from a larger population
• distance from Africa = decrease in phonemic complexity

Question 15

Is there a genetic defect that affects language?

Answer 15

Romanian family where people affected had no language:

• inheritence pattern (autosomal dominant)
• neurological deficit affecting speech
• mapped to FOXP2
• not right
• poor motor skills, cognitive etc - may be important for brain development not just language
• no ‘language gene’