1 Language disorders We can learn a lot by looking at system failure –Which parts are connected to which Examine the relation between listening/speaking.

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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– 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 comprehensionthis 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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ImagingBroca’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

AUDITORYANALYSIS

PHONEMEBUFFER

AUDITORYINPUT

LEXICON

SPEECHOUTPUTLEXICON

SEMANTICSYSTEM

Speech

PA

TH

1

PATH 2

PATH 3

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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 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

• 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 mid-

adolescence (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