Language disorders

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Language disorders

• We can learn a lot by looking at system failure
• Which parts are connected to which
• Examine the relation between listening/speaking
  disorders and physiology
• Careful to not confuse individual difference with
  disorder!
• Most useful clinical information comes from
  lesions

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Researching cognitive neuropsychology

• To show that 2 functions are found in separate
  areas of the brain, you need 2 cases
• One where A is fine, B is impaired
• One where B is fine, A is impaired
• This shows that the two functions are independent
• double dissociation

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Separating of speech production comprehension

• We consider speech production comprehension as
  spearate
• What is the evidence?
• There exists a double dissociation between the
  functions
• Brocas aphasia (production)
• Wernickes aphasia (comprehension)
• Each associated with a specific brain site

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Brocas aphasia

• Symptoms slow, difficult speech, little syntax,
  disjointed
• "Son ... University ... Smart ... Boy ... Good
  ... Good ... "
• Associated with left posterior frontal lobe
  (motor cortex)
• Side can change
• Comprehension completely intact
• Know what to say, cant say it

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Wernickes aphasia

• Symptoms word deafness, cannot understand
  syntax, word salad, poor comprehension
• this is .... mother is away here working her
  work out o'here to get her better, but when she's
  looking, the two boys looking in other part. One
  their small tile into her time here.
• Associated with the left temporal lobe (connected
  to visual auditory cortices)
• Speech production normal
• Rate, intonation, stress all OK

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Relevant anatomy
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Conduction aphasia

• Symptoms good comprehension, fluent speech, poor
  reading, poor repetition, word transpositions
• Associated with left arcuate fasciculus
• Connects Wernickes and Brocas areas
• Shows connections as important as processing sites

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L. Arcuate Fasciculus
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Imaging
Brocas aphasia case
Conduction aphasia
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Positron Emission Tomography (PET) scan
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Modelling from neurological data

• Deficits can give a lot of information
• Writing production, speech, production,
  listening, reading, plus combinations!
• Some deficits only apply to classes of words (eg.
  proper noun anomia)
• Combine abstract cognitive models with clinical
  data to produce models
• Cognitive neuropsychology!
• Understand how brain injury can impair cognitive
  functioning

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Ellis Young (1996) word processing

• Three path information processing model
• Three different ways of producing a word
• One for normal speech one for repetition a
  third hypothetical one
• Explains normal speech, speech pathology,
  repetition of unknown words

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Ellis Young (1996)
Auditory signal
AUDITORY ANALYSIS
PATH 3
PATH 2
AUDITORY INPUT LEXICON
PATH 1
SEMANTICSYSTEM
SPEECH OUTPUT LEXICON
PHONEME BUFFER
Speech
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Applications of the model

• PALPA evaluations
• Psycholinguistic assessments of language
  processing in aphasia
• Various listening repetition tasks to follow
  all 3 paths
• Language tasks to check which node of the model
  is failing
• Model can also be used to understand pure word
  meaning deafness
• Cannot give a words meaning, but can repeat and
  write it down

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Pure word meaning deafness

• Patients can usually do lexical decision tasks OK
• Word/fake word descrimination
• Suggests the Auditory input lexicon is OK
• Understanding of written material may be
  unimpaired semantic system OK
• Deficit thought to lie in connection between
  auditory input lexicon and semantic system

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Auditory Phonological aphasia

• Can be well explained by the EY model
• Syndrome can read and write, difficulty with
  place names and scientific terms
• Jargon aphasia proper noun anomia
• Can easily repeat real words, but not non-words
• Route via auditory input lexicon is OK
• Route via auditory analysis system and auditory
  buffer impaired

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Deep dysphasia

• Extremely rare catastrophic speech disorder
• Unable to repeat non-words
• Frequent semantic errors on words (eg. yellow
  for blue)
• Abstract words more difficult to repeat that
  concrete ones
• EY96 model explains this
• Bad connection between semantic system and
  auditory input lexicon
• Bad route between auditory analysis phonemic
  buffer

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Functional plasticity

• Cortex areas become specialised
• Not completely set
• At an early age, functions can move from place to
  place (functional plasticity)
• Language can be partly moved to right hemisphere,
  or distributed between them
• Functional deficit at an early age can be
  overcome
• Functions can be partly relocated (neural
  specificity)
• Not complete functioning, but enough to cope

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The Kennard Principle

• Functional plasticity decreases with age (Kennard
  principle)
• Not possible after mid-adolescence (14-16)
• Certain functions lose plasticity first (Lurias
  theory)
• Not quite simple sometimes insult at an early
  age is worse (leukemia patients)
• Problem hierarchy of systems
• Neural systems are hierarchically arranged
• If a required system is damaged, moving the
  function someplace else will not help