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.



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.



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.



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´.



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



Fig 1: Connectionist model of language



Fig 2: Lichtheim & Wernicke¶s nosological scheme



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)



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



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)



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.



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.



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.



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



A cognitive neuropsychological framework for

understanding language disorders

Figure 3 shows a

modular system or

µfunctional

architecture¶ for

identifying and

producing spoken

words



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



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



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.



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¶.



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



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



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.



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



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



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.



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

aphasia linguistic

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