lecture 15 Flashcards
Language when do humans begin to use language? which brain regions are required for language? do only humans use "generative" language? why is human language unique? when did humans begin to use language? what brain mechanisms underlie human language?
What are the three categories of aphasia?
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
When does language develop in humans?
(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
Which areas of the brain are involved in language?
- 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)
What is a non-anatomical approach to defining areas of the brain related to speech?
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
What are the characteristics of Broca’s and Wernicke’s aphasias?
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
How might conduction aphasia be caused?
- disconnecting Wernicke’s and Broca’s area (arcuate fasciculus)
What is alexia? What are its symptoms?
- 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
How is language localised?
- 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
What is hemispheric asymmetry?
- 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)
What are the functions of the left and right hemispheres?
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
Do other animals have “generative” language?
- 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
What is it that our nervous system has that allows us to create language as we know it?
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
What did a recent study (by Dunn and others show?
- 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.”
What is the population founder effect?
- 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
Is there a genetic defect that affects language?
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’
