aphasia linguistic
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8/8/2019 Aphasia Linguistic
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Aphasia
Def of Aphasia:
A disorder of language that is neurogenic
(caused by brain disease or injury), whichinvolves the symbolic use of sound (i.e.
Language in the meaningful sense of the
word). Is not due to deafness or motor- paralysis, mental retardation etc.
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Differential diagnosis and disorders
which make it hard to identify aphasia
Dysathria ± poor articulation of speech due to
slurring or fragmentation of the sound structure
of speech. Is a motor problem due to poor
coordination of breathing and speech muscles.Cause slurred speech and staccato speech.
Apraxia ± disorders of skilled movements. Can
include symbolic movements. Cause by left
parietal lesions. Some apraxias particularly
affect the ability to speak, e.g Buco-facial
apraxia.
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Language is assessed in terms of :
Language comprehension: understanding
language as opposed to hearing or seeing it
Language production: speech output, not just the utterance of noise, but the utterance
of meaningful noise, and also the
spontaneous production of language
R epetition: copying of language.
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Other important terms
Anomia: ability to name things, tested onconfrontation
Word-finding difficulties: difficulty finding the particular word you are looking for, seen in the
patient¶s spontaneous speech.Paraphasia (next to speech) ± distortions in
speech output
Semantic paraphasias: say a word that is
meaningfully related to the word you want to say.E.g. ³whiskey´ when you want to say ³wine´.
Literal paraphasias: is phonologically differentfrom the word you want to say. E.g. ³broddel´
instead of ³bottle´.
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Alexia ± aphasia for written language (can¶t
comprehend)Dyslexia ± milder form of the above
Agraphia ± disorder of writing, can¶t
produce (write) language.
You can have an Alexia/agraphia without
aphasiaBut you should not find an aphasia without
an alexia/agraphia
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Fig 1: Connectionist model of language
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Fig 2: Lichtheim & Wernicke¶s nosological scheme
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Wernicke¶s aphasia
Can¶t comprehend, can¶t repeat, can s peak s pontaneou sly
Spontaneous speech is however not normal
Is fluent, but is paraphasic, semantically paraphasic in
particular. In extreme cases, word salad.Make a particular type of literal paraphasic errors
(neologism ± make up new words, predominantly by putting old words together - Jargon aphasia.
Not always entirely aware that they are not makingsense, because their comprehension is impaired.
Lesion site: left primary projection cortex (Wernicke¶sarea)
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Broca¶s aphasia
Speech out-put problems
Output is non-fluent, not only i.t.o. few words per minute
(i.e. less than 60), but also in terms of short phrase length
which leaves out connecting words and overemphasises
of nouns. This leads to telegramatism.
Effortful and halting speech.
Lesion site: Just in front of motor area ± Broca¶s area: i.e.
Posterior part of the inferior frontal convulsionSame difficulties usually extend to written language
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Conduction Aphasia
C ompr ehension and Pr od uction is still r elatively intact R epetition is impaired ± sound images received by
Wernicke¶s area can not be transmitted forward toBroca¶s area to be produced
However, spontaneous output is also not normal Is paraphasic, but predominantly of literal type. This
takes a particular form in that they will approximate theword closer and closer and sometimes they will get there
Lesion site: Posterior temporal lobe or insular cortex(track of fibres (white matter) that connects Broca¶s &Wernicke¶s area (arcuate fasciculus)
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Transcortical sensory aphasia (TCSA)Disruption to links between Wernicke¶s area and the
concept centre
Unable to comprehend, but still abl e t o pr od uce and t o r epeat
Circumlocutory
±
go around words. Leave out concretewords, but full of connectives
Speech is fluent, but empty of meaning
Severe word-finding difficulties, specifically for concrete
words and nouns - Use phrases like ³thing a ma jig´ and³you know what´
Pathology: Alzheimer¶s patients in the 2nd stage of disease.
Lesion:
From Wernicke¶s upwards towards parietal lobe.
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Transcortical motor aphasia (TCMA)
Due to damage to fibres linking the concept centre withBroca¶s area
Non-fluent speech output
Tend to say very little, lack of initiation of speech
Paucity of spontaneous output
C an r epeat
Often has a compulsion to repeat back what is heard ± echolalia
Lesion: Damage is to fibres that lead to Broca¶s area. Isnot always in transcortical area, lesion may also be insupplementary motor area.
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Other types not included in
Lichtheim¶s model
Global aphasia
Poor production and comprehension
Damage to both Wernicke¶s and Broca¶sarea
Often a stroke may initially be cause a
global aphasia and then recover to aBroca¶s or Wernicke¶s aphasia.
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Mixed transcortical aphasia
Affect both transcortical motor andtranscortical sensory fibres.
Caused by watershed infractions of middle cerebral area (thus speech area isisolated)
Can repeat, but can¶t understand or
produce.
Repeat quite a lot ± echolalia
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A cognitive neuropsychological framework for
understanding language disorders
Figure 3 shows a
modular system or
µfunctional
architecture¶ for
identifying and
producing spoken
words
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Acoustic/auditoryanalysismodule:
responsible for converting the speechsignal of a word into a phonemic code
The Phonemic code canthen access that word¶sentry in the auditoryinput lexicon
The auditory inputlexicon is a store of information about thesound of each word that
we know
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The meaning of the
activated word can
become available within
the semantic system
Semantic context can
also aid wordidentification
Both the auditory input
lexicon and the semantic
system have links withthe phonological output
lexicon
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The phonological outputlexicon comprises of info
about how to say all thewords that we know.
Its output goes to aphonemic response bufferwhere the info about how to
say the word is held untilwe are ready to say it.
There is also a two-waylink between the
phonological outputlexicon and the phonemicresponse buffer - allowsthe two modules to becomeinteractive in the generation
of speech.
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The direct link from theacoustic analysis system to
the phonemic response buffer via the acoustic to phonological conversionsystem. Allows us to repeatnonsense words such as
BLIG and SPO NE. Info can also flow from the
phonemic response buffer back to the acoustic analysismodule ± this allows
phonemic info to berecycled in the system and
provides the basis for µinnerspeech¶.
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Disorders of Language (a
psycholinguistic approach)
Pure word deafness
This disorder provides evidence for the
existence of a separable acoustic/auditory
analysis module
Disorder is characterized by an inability tounderstand spoken words despite being
able to read, write and speak normally
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Can recognize music andenvironmental sounds,BUT has a specific problem in perceivingspeech-like sounds.
The perceptual deficit
responsible for pureword deafness involves adeficit in phonemicprocessing
I.e. the patient is unableto segment a string of speech sounds into itsconstituent phonemes
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Pure word meaning
deafness Patient is unable to understand
what a word means even thoughhe/she is able to repeat and writewords to dictation accurately
Auditory lexicon is intact ± candistinguish between real words
and non-words (i.e. still has ainternal representation of eachknown word).
Semantic system is also intact,
given that he/she is able tocomprehend written material
Deficit lies in the connection between the auditory inputlexicon and the semantic system.
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Auditory phonological agnosia
This disorder providesneuropsychological support for the existence of a direct routbetween the acoustic analysismodule and the phonemic
output buffer, i.e. that part of thesystem that allows us to repeatunfamiliar and non-words.
Patients loose the ability totranslate acoustic inputs intospeech ± the only way in whichwe can repeat non-words. Theonly route for repetition becomesvia the auditory input lexicon
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Anomia
Is a condition in which the patient has problemsfinding the right word
Patients often resort to elaborate
circumlocutionsE.g. for ³doll´ ± they may say ³solid
representation of a baby´
Analysis of this disorder has been the primary
basis for proposing an auditory output lexiconDistinction between semantic anomia and word
selection anomia
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Semantic anomia: Patient
has problems finding words because of a semanticdisturbance ± makesemantic errors
In word selection anomiathe semantic input appearsintact (since these patientscan understand what peopleare saying to them) and the
defect lies within the phonological output lexiconitself.
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Neologistic Jargonaphasia
(Wernicke¶s aphasia revisited)
These patients may suffer from a form of word
selection anomia (which would explain the
neologisms they make)
Is exacerbated by a failure to monitor the lexicalstatus of words they produced ± something
termed µphonological derailment¶
It may be that attention may play a significant
role in the fact that these patients are unable to
monitor the errors they make when speaking
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