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
– Broca’s aphasia (production)
– Wernicke’s aphasia
(comprehension)
– Each associated with a specific
brain site
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Broca’s 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, can’t say it
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Wernicke’s 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 Wernicke’s and
Broca’s areas
• Shows connections as
important as processing sites
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L. Arcuate Fasciculus
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Imaging
Broca’s 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 1
AUDITORY
INPUT
LEXICON
SEMANTIC
SYSTEM
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 word’s 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
E&Y 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
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impaired
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
• E&Y96 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 midadolescence (14-16)
– Certain functions lose plasticity
first (Luria’s 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
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