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STNS STNS 60603: Advanced and Contemporary 3: Advanced and Contemporary NeurobiologyNeurobiology

TopicTopic:: NeurolingisticsNeurolingistics

Lecturer: Dr. Naiphinich Kotchabhakdi Ph.D.Neuro-Behavioural Biology Center,Institute of Science and Technology,Mahidol University, Salaya,Nakornpathom 73170 Thailand

ContentsContentsThe meaning of Neuro linguistics.Brain and language.Neuroanatomy of the language.Brain and the linguistic capacity.Language and Brain Lateralization.An amazing fact.Second Language acquisition and Brain plasticity.Magnetoencephalogram (MEG)Visual languageAphasia

What is the Meaning ofNEUROLINGUISTICS ?

Neurolinguistics is the branch of linguistics and neuroscience that is concerned with the brain mechanism and that underlines the acquisition and use of human language, through the study of the neurobiology of language.

Brain and Language,Historical backgroundHistorical background

The hypothesis which states the brain is the source of language has started by the ancient Egyptians and the ancient Greeks.

The assumption reoccupied people’s attention againwhen Paul BrocaPaul Broca introduced what is called ““BrocaBroca’’s s aphasia,aphasia,”” and stated that we speak with the left hemisphere in 1869.

Carl WernickeCarl Wernicke introduced another variety of aphasia “language disorder” that occurred to patients with lesions.

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Neuroanatomy of the LanguageIt is now accepted that the Broca’s area and the Wernicke’s area are in the left hemisphere of a right-handed person and are the two brain regions most closely associated with language ability.

Broca’s area and “function areas”Lichtheim (1885)

Concepts

Verbal motor memory Acoustic word memory

Brain and the Linguistic Capacity

The fundamental component of linguisticcapacity is the ability to ‘name’ or/and to associate a symbol to an object or an action. That ability is dependant on the ability to form cross-modals associations between modalities (Geschwind, 1964Geschwind, 1964).

Therefore, nonhumans are incapable, even with intense training, of forming the type of modal representation necessary for metaphorical matching.

Language And Brain Lateralization

The human brain is separated by a longitudinal fissure which separates the brain into two distinct cerebral hemispheres. These hemispheres are connected by “Corpus Callosum”Language, as a reasoning function, is lateralized to the left hemisphere of the brain.

Left hemisphereLeft hemisphere Right hemisphereRight hemisphere

Corpus CallosumCorpus Callosum

Language And Brain Lateralization

Realizing brain function laterality is credited to Paul Broca who built his research on ””TanTan””,, a patient who had speech deficit in 1861. After Performing a post-mortem autopsy, Brocadetermined that Tan had a lesion in the left cerebral Tan had a lesion in the left cerebral hemisphere. This area is called hemisphere. This area is called ““BrocaBroca’’s areas area””..Broca included that deficit in speech production, Broca’s aphasia, is caused by damage in Broca’s area

BrocaBroca’’s Areas Area

Language And Brain Lateralization

WernickWernick’’ee AreaArea

In 1874,In 1874, WernickeWernicke announced another variety of aphasia, announced another variety of aphasia, that occurred in patients with lesions in the back portion of tthat occurred in patients with lesions in the back portion of the he left hemisphere, known asleft hemisphere, known as ““WernickeWernicke’’s Areas Area””..

Unlike BrocaUnlike Broca’’s patients, those patients spoke fluently but s patients, those patients spoke fluently but they had numerous instances ofthey had numerous instances of lexical errors lexical errors ‘‘word word substitutionssubstitutions’’, or what is known as Wernicke, or what is known as Wernicke’’s aphasias aphasia..

Those patients also hadThose patients also had difficulty in comprehending speech.difficulty in comprehending speech.

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An Amazing Facts“When baby utters his first “Mama” at age one, adults exult that he has finally begun learning to speak. But his lessons in language began long before. Even in the womb, the infantEven in the womb, the infant’’s neural and s neural and vocal senses are being actively developedvocal senses are being actively developed”” (John L Locke, (John L Locke, 1994).1994).

Locke and others found out that the right hemisphere plays an Locke and others found out that the right hemisphere plays an important role in language during the first three to seven important role in language during the first three to seven years of life.years of life.

In the act of speaking, the right side of an adultIn the act of speaking, the right side of an adult’’s mouth s mouth tends to open first because motor control of the right side of tends to open first because motor control of the right side of the body and control of the speech are both vested in the body and control of the speech are both vested in the the left hemisphere of the brainleft hemisphere of the brain..

In young children, both sides of the mouth are opened at the same time because the right side of the brain which controls theleft side of the mouth houses speech centers

Second Language Acquisitionand Brain Plasticity

Is human skill to learn more than one language mediated to functional or structural change in the brain?

* Learning a second language increases the density of Learning a second language increases the density of the left inferior partial cortex. the left inferior partial cortex.

* The degree of structural reorganization in this region is modulated by the proficiency attained and the age at acquisition.

So far…

Brain divided into two hemispheres.Primary language functions (syntax, phonology, morphology) appear to be mostly dealt with by the left hemisphere.Looking at linguistic deficits (aphasias) and the corresponding physiological causes (lesions) can help determine what parts of the brain appear to be functionally responsible for what parts of the language system.

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Broca’s area and “function areas”Lichtheim (1885)

Concepts

Verbal motor memory Acoustic word memory

Some attested aphasia types

L1 and L2 seem to be able to recover independently.It appears to sometimes make a difference whether the language was learned by reading or speaking (implicit vs. explicit long term memory?)Cases so far: recovering non-communication languages first, differential effects from the same lesion, pathological code-mixing, alternating antagonism.

Child aphasia

Acquired aphasia during childhood is almost never fluent (mutism), but they recover rapidly (lasting effects generally only slight word-finding and vocabulary difficulties).Recovery is faster, better than in adult acquired aphasia, but not complete.Early enough, right hemisphere can take over language functions after a serious loss in the left hemisphere, but it doesn’t do as good a job.

Child aphasia

Lenneberg’s summary of the results of left hemisphere lesions as a function of age:• 0-3mo: no effect• 21-36mo: all language accomplishments disappear;

language is re-acquired with repetition of all stages.• 3-10ye: aphasic symptoms, tendency for full recovery• 11ye on: aphasic symptoms persist.

Basis for his view that lateralization was tied to critical period.

Translation

Aphasic deficits in translation capabilities suggest that translation too might be a separate system.Reported cases of loss of ability to translate (though retaining some abilities in each language).Other reported cases of loss of ability not to translate; Case: Perecman (1984): patient would always spontaneously translate German (L1) sentences uttered into English (L2) immediate afterward, yet could not perform translation task on request.

TranslationTranslation

Sometimes this can happen even without comprehension; Case: Veyrac(1931): patient (English L1, French dominant L2), could not understand simple instructions in French, but when instructed in English would spontaneously translate them to French and then fail to carry them out.

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Paradoxical translationParadoxical translation

Case: Paradis et al. (1982). Patient switched (by day) between producing Arabic and producing French. When producing only Arabic, she could only translate from Arabic into French; when producing only French, she could only translate from French into Arabic.

Gomez-Tortosa et al. (1995)

22 yo, RH woman raised until 10 in Bolivia (Spanish L1), in US for past 12 years (fluent English L2). Had a brain problem which required surgery in a language area. Wada test in English showed LH dominance.2mo: Had trouble finding words in Spanish, frequently used nonwords approximating Spanish words. No noticable problems with English. Tests confirmed.Conclude: both languages in dominant hemisphere. Each language in different area?

Bilingual representationBilingual representationA number of dissociated phenomena in bilingual aphasia studies.• Sometimes only one language returns, not always

the L1• production and comprehension and translation

seem to be separable, and even by language.• Monolingual aphasia studies seem to correlate

lesion localization with function.• Not much evidence for localization differences

between multiple languages per se.• Some evidence for localization differences

between types of learning? (written, conscious vs. unconscious, implicit vs. explicit memory?)

Bilingual representation

Given the postmortem studies showing no real morphological differences between monolinguals and polyglots, the most consistent picture seems to be one of shared neural architecture with inhibition between languages.Choice of language A inhibits access to grammar, vocabulary of language B during production.Comprehension is often spared even in the face of production inability, suggesting that the same kind of inhibition does not hold of comprehension.

Bilingual representationBilingual representation

Many of the aphasic symptoms in production can be described in terms of changing inhibitions; the lesion disrupts the balance of inhibition and excitation between neural structures, leading to:• loss of inhibition (pathological mixing)• heightened invariant inhibition (fixation)• shifting inhibition (alternating antagonism)• psychological inhibition (repression)

SubsystemsSubsystems

There also seem to be several subsystems which can be individually impaired.• Naming, concepts• Fluency of production• Ability to retain and repeat• Translation from L1 to L2• Translation from L2 to L1

Some of these seem to correlate with localization differences.

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More modern methods and results

Recording electrical activity in the brain can also help us see which parts are used in language tasks• Electroencephalogram (EEG)• Event-related potentials (ERP).• Magnetoencephalogram (MEG)

Functional brain imaging• Computer axial tomography (CT) (X-rays)• Positron emission tomography (PET)• Functional magnetic resonance imaging (fMRI)

Findings and Evidence from

Functional Brain Imaging

Dimensions of the Territoryof

Neurolinguistics

Language and music (PET)

http://encarta.msn.com/media_461519549_761555359_-1_1/Positron_Emission_Tomography.html

More modern methods and results

Recording electrical activity in the brain can also help us see which parts are used in language tasks• Electroencephalogram (EEG)• Event-related potentials (ERP).• Magnetoencephalogram (MEG)

Functional brain imaging• Computer axial tomography (CT) (X-rays)• Positron emission tomography (PET)• Functional magnetic resonance imaging (fMRI)

MEG at Harvard/MGH

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MEGex. Pylkkänen, Stringfellow, Kelepir, & Marantz (2000)

BELL RTstimulus

M180: A visual response unaffected by stimulus properties such as frequency (Hackl et al, 2000), repetition (Sekiguchi et al, 2000, Pylkkänenet al 2000) and phonotacticprobability/density. Clearly posterior dipolar pattern.

M250: A component between the M180 and M350. Also insensitive to variations in stimulus properties that affect lexical access. Clearly distinct from the M350 as these two responses have opposite polarities. Processing of orthographic forms?

M350: The first MEG component sensitive to manipulations of stimulus properties affecting lexical activation. Working hypothesis: this component reflects automatic spreading activation of the lexicon –at signal maximum all the competitors are activated.

Postlexical processes including the word/nonword decision of the lexical decision task.

Imaging methods compared Temporal Resolution of MEG

The temporal order of activation of areas in a pattern can be discernedThe temporal resolution of MEG is excellent, as compared to fMRI or PET, which both carry a delayOnly with MEG can we detect the activation of several brain regions as they become active from moment to moment during a complex function such as recognition

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Time course of activation (MEG)

The magnetic fields recorded in MEG are evokedActivation at each point in time is recorded (millisecond sensitivity)We can follow the activation of a source across timeSources of early components of Evoked Fields circumscribe the modality-specific sensory areasSources of late components circumscribe different sets of brain regions (mostly association cortex)• - These sets or activation patterns are function- (or

task-) specific

An MEG study

Levelt, Praamstra, Meyer, Helenius & Salmelin, J.Cog.Neuroscience 1998

Naming animals from visual (picture) input

L

R

Speech recognition: MEG results

Hemispheric Asymmetry Wernicke's Area

Variability in location of Wernicke’s area(different subjects)

From MEG lab, UT Houston

Wernicke’s area in bilinguals

From MEG lab, UT Houston

MEG and localization of phonemes

Claim: The relative positions of neural representations for vowels in Wernicke’s area correlate with the relative positions of the vowels in articulatory space• Obleser, Elbert, Lahiri, & Eulitz, 2003• Obleser, Lahiri, & Eulitz, 2004• Obleser, Elbert, & Eulitz, 2004• Shestakova, Brattico, Soloviev, Klucharec, &

Huotilainen, 2004• Eulitz, Obleser, & Lahiri, 2004

This finding needs to be replicated!

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MEG and localization of phonemes

Wernicke’s area may be organized phonemotopicallyThe anterior-posterior axis corresponds to the backness of a vowel – the more back the vowel, the more posterior the source locationThe superior-inferior axis corresponds to the height of a vowel (inverse relationship) – the higher the vowel, the more inferior the source location of that vowel

From: Ladefoged, P. (2001). Vowels and Consonants: An Introduction to the Sounds of Languages. Malden, Massachusetts: Blackwell Publishers, Inc.

An MEG Study of Neural Plasticity(in progress at UT Houston)

Investigation of the reorganization of the brain following stroke

Language, motor, somatosensory, attention

Subjects tested at 3 months and 10 months post-stroke (within the acute period)

Some of the aphasic subjects will undergo constraint-induced language therapy (CILT) during the chronic period (10 months on)

Testing before, immediately after, and then one month after the CILT

Cortical Processing of Real Words, Pseudowords, and Nonwords (Novak 2006)

Rice Linguistics dissertation, Barbra NovakMEG study of speech perceptionCompared three kinds of speech input• Real English words – phonotactically and

semantically acceptable• Pseudowords – phonotactically acceptable, but

meaningless – e.g. bleem• Nonwords – phonotactically unacceptable and

meaningless – e.g. mzop

Novak 2006 – General Method

Passive listening taskLooking for differences in the localization of processing in two time periods (e.g., early (low-level) vs. late (higher-level) processing)

Real words, Pseudowords and Nonwords: Previous research

Increased left superior temporal gyrus (STG) activity in response to pseudowords as opposed to real words

• Kotz et al., 2002; Wydell et al., 2003; Simos et al., 2000

Increased left middle temporal gyrus (MTG) activity in response to real words

• Binder et al., 2000; Kotz et al.; Xiao et al., 2005; Sarkari et al., (in press); Papanicolaou et al. (in press)

Increased left inferior frontal gyrus (IFG) activity in response to pseudowords as opposed to real words

• Xiao et al., 2005

Methodology

Six subjects (3 females) ranging in age from 50 to 56 years (mean = 53) Right-handed • Edinburgh Handedness Inventory (Oldfield,

1971) No history of neurological diseaseNormal hearing Native English speakersAll “linguistically naïve” in that they never received any formal linguistics trainingSubjects familiar with Polish or any other Slavic language were not included in this study

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Methodology

Passive listening task during which they were asked to listen very carefully and pay close attention to auditorilypresented words

All stimuli were monosyllabic with an initial consonant cluster• Because MEG is temporally sensitive, the

difference between the phonotacticallyacceptable words (real words and pseudowords) and the phonotacticallyunacceptable nonwords needed to occur at the same point in time (the difference being the phonotactic legality of a consonant cluster)

Methodology

The pseudowords were developed by manipulating one or two of the phonemes of the real words• None of the pseudowords included a real word (e.g., “trun”

was not used because “run” is included within it)The nonwords used in this study were based on Polish phonology. Polish phonology was chosen for this task because many phonemic combinations allowable in Polish violate English phonotactics• For example, the Polish word bzdura (/bzdura/) has a

consonant cluster bzd (/bzd/), a combination not allowed in English

Any subjects familiar with Polish did not participate in this study, since the use of Polish phonology in the nonwords was reliable only if the subjects had no knowledge of Polish

Methodology

Why a passive listening task?During a typical auditory lexical decision task, the subject is required to respond in some manner (e.g., via pressing a button) when he/she hears one type of word • e.g., in the context of this experiment, pressing the

button in response to the real words as opposed to the pseudowords or the nonwords

However, finger movement associated with the button press causes frontal lobe activityFrontal activity may occur in response to one or more lexical conditions in the present task• Newman & Twieg, 2001; Kotz et al., 2002; Specht et al.,

2003; Xiao et al., 2005It is possible that frontal activity from a button press might have masked frontal activity occurring in response to the stimuli

Methodology

Each subject was tested on five separate occasions

Test sessions separated by at least one week

Auditory stimuli varied across test sessions• The 441 words for each test session were taken from a

pool of 1119 words (373 of each type of word)

These two measures were taken to ensure that learning effects were minimized

Real words, Pseudowords, and Nonwords

Dipolar source localizations of real words, pseudowords, and nonwords in one subject (30-800 ms) (blue = real; green = pseudo; red = non)

Real words, Pseudowords and Nonwords: EARLY

The first 150 ms of activation includes the primary auditory response (N1), which occurs at approximately 100 ms Because the primary auditory response is the most basic and preliminary response to an auditory stimulus, it should remain unaffected by the type of stimulus (e.g., linguistic or nonlinguistic) The processing that differentiates linguistic from nonlinguistic stimuli occurs after the primary auditory response Therefore, the lack of a significant difference among conditions found in the present study is consistent with what is expected to transpire during the most basic level of auditory processing

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Early STG activation

0

5

10

15

20

left right

Hemisphere

mean dipoles

RealPseudoNon

Real words, Pseudowords and Nonwords: LATE

STG, MTG, frontal lobe, and insulaSTG and MTG• main effect of area [F(1,5) = 16.064, p = .010]• no interaction effects of area • no main effects of hemisphere or condition

frontal lobe and insula• no main effect of area [F(1,5) = .169, p = .698]• no main effect of hemisphere [F(1,5) = 2.869, p = .151]• no main effect of condition [F(2,4) = 2.909, p = .166]• no interaction effects

STG was significantly more active than the other areas, indicating that the most robust high-level linguistic processing associated with perceiving auditory stimuli occurred in STG

Late STG, MTG, frontal, insula activation

0

5

10

15

20

25

30

35

40

45

50

STG MTG Fron Insu STG MTG Fron Insu

left right

ROI and hemisphere

mean dipoles

RealPseudoNon

Real words, Pseudowords and Nonwords: LATE

No significant effects of condition or hemisphere were found

However, some very important trends in the activation patterns were apparent

Middle temporal gyrus

Real words and pseudowords activated left MTG more than right MTG

Nonwords produced bilateral MTG activity

Laterality index • Index values closer

to 1 indicate a higher degree of left lateralization; index values closer to 0 indicate bilateral activation

0.069Non

0.650Pseudo

0.546Real

INDEX (L-R)/(L+R)CONDITION

-1

-0.8

-0.6

-0.4

-0.2

0

0.2

0.4

0.6

0.8

1laterality index

RealPseudoNon

Middle temporal gyrus

0

2

4

6

8

10

12

Non Pseudo Real

condition

mean dipoles

leftright

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Middle temporal gyrus

The left lateralization of MTG activity for real words is consistent with previous research • Binder et al., 2000; Kotz et al., 2002; Xiao et al.,

2005; Sarkari et al., in press; Papanicolaou et al., in press

However, the left lateralization of MTG activity for pseudowords has not been previously reportedAforementioned studies found that left MTG activity was greater for real words than pseudowordsNevertheless, in the present study, real words and pseudowords elicited the same level of activity in left MTG

Conclusions

The distinction between nonwords and pseudowords and real words was most apparent in MTG• Only the pseudowords and real words

demonstrated left-lateralized MTG activity• Semantic processing required for

differentiating the semantically void pseudowords from the semantically rich real words occurred in left MTG

• The nonwords did not cause left-lateralized MTG activity, indicating that they were identified as non-linguistic stimuli before reaching the semantic processing stage

More modern methods and results

Wada test.Wada test. Sodium amytal causing temporary neural paralysis can simulate a possible aphasia (in order to avoid it during neurosurgery).Electrical stimulation. Similar but shorter term, more localized.Results are mainly in line with other knowledge, but the problem with these tests is that a) electrical stimulation is hard to repeat (imprecise), b) both methods can only be used on people waiting for neurosurgery who may have abnormal brains.

Ojemann & Whitaker 1978

•Dutch inhibited•English inhibited•Both inhibited•Neither inhibited

•For whatit’s worth…

Differences between bilingual and monolingual representations

Best guess at this point is that there is overlap—the several languages make partial use of physiologically distinct areas of the brain, but also share a lot in common.Some evidence that second language has a right-hemisphere component, more diffuse than first language, although directly contradictory findings have also been reported.The state of things is actually a little bit disappointing—but it turns out to be hard work..!

Hernandez, Martinez, Kohnert (2000)

fMRI study of Spanish-English (before 5) bilinguals. Presented with pictures, and heard either diga or say, and were to name the picture in the language matching the cue.• The results revealed no differences between the two languages in

our our particular regions of interest, which included the dorsolateral prefrontal cortex (areas 46 and 9), the supramarginal gyrus (area 40), the inferior frontal gyrus (areas 44 and 45), and the superior temporal gyrus (area 22). This is consistent with previous studies which have found that bilinguals who learn a second language very early in life show few differences in the pattern of activation for each language.

• The only area that revealed increased activity for language switching relative to singe-language processing was the dorsolateral prefrontal cortex.

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Wuillemin et al. (1994)

36 Papua New Guinean students (gender split, all RH’ed, spoke 2-9 languages, fluent in English, which was language of instruction). Compared across three “English acquisition” age groups (0-4, 5-8, 9-12).Tachistoscopic task. English: Found not much hemisphere difference across groups; RVF was a tiny bit faster, 9-12 overall slower, no longer an RVF advantage. Tok Pisin: 0-4 looks same, 9-12 LVF advantage. Both: increased RH involvement.

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What is Aphasia?Aphasia is a loss of the ability to produce and/or comprehend language, caused by damage to brain areas specialised for these functions. These areas are almost always located in the left hemisphere and this is where the ability to produce and comprehend language is found. However, in a very small number of people language ability is found in the right hemisphere. Most commonly it is seen in adults who have suffered a stroke, a brain tumor, infection or head injury. The type of language disfunction depends on the location and extent of the damaged brain tissue.It is very rare in children.

Symptoms:

Inability to comprehend languageInability to pronounce Inability to form wordsInability to name objectsPersistent repetiotions of phrases Paraphasia (substitution of letters or words)Agrammatism (inability to speak in a grammatically correct form)Uncompleted sentencesInability to writeInability to read

Classification of aphasia

BROCA’S APHASIA & WERNICKE’S APHASIA

Broca’s aphasia(Expressive aphasia)

It is caused by a damage to anterior regions of the brain including the left inferior frontal region known as Broca’s area.Sufferers of this form of aphasia exhibit the common problem of agrammatism. For them speech is difficult to initiate, non fluent. Language is described as telegraphic and reduced to disjointed words. Sentence construction is poor, omitting function words and inflections.

Ex. Yes.. ah.. Monday…Dad and Peter H. and Dad…hospital…and Wednesday.. Wednesday, nine o’clock.. and Thursday.. ten o’clock, ah doctors.. two doctors.. and ah.. teeth.. yah

Here the patient is trying to explain how he came to the hospital for dental surgery. In extreme cases patients may be only able to produce a single word. The most famous case of this was Broca’s patient Leborgne, nicknamed “Tan”, after the only syllable he could say. Comprehension:Patients who recover say that they knew what they wanted to say but could not express themselves.

Wernicke’s aphasia(Receptive aphasia)

It is caused by a damage to posterior part of the of the superior temporal gyrus of the dominant hemisphere.Individuals with Wernicke’s aphasia may speak in long sentences that have no meaning, add unnecessary words, substitute a word for another and even create neologisms.

Ex. I called my mother on the television and did not understand the door. It was too breakfast, but they came from far to near. My mother is not too old for me to be young.

Comprehension:Patients who recover from Wernicke’s aphasia report that, while aphasic, they found the speech of others unintelligible and they could neither stop themselves nor understand their own words.

Anomic aphasia & Global aphasia

Anomic aphasia is the least severe form of aphasia. Patients have difficulty in remembering and using the correct names for particular objects, people, places, or events. The subject speaks fluently and grammatically, the only deficit is trouble with word-finding. Global aphasia is the result of a severe and extensive damage to the language areas of the brain. Patients loose almost all language functions, both comprehension and expression. They cannot speak or understand speech, nor can they read or write.

Primary aphasia & Secondary aphasiaPrimary aphasia & Secondary aphasiaPrimary aphasia is due to problems with language-processing mechanisms.Secondary aphasia is the result of other problems, like memory impairments, attention disorders or perceptual problems.

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Acquired Childhood Aphasia

Acquired childhood aphasia is a child’s partial or total loss of the ability to understand words and use language because of a brain injury. Acquired means that it occurs after the child has begun developing language skills. One form of acquired childhood aphasia is called LKS, Landau-Kleffner syndrome.Aphasia can occur in children who have experienced head trauma, encephalitis, a brain tumor, stroke, or other brain disorders. Researchers have found no connection between aphasia and age and gender. However LKS is usually seen in children between the age of 3 and 7.Symptoms in children can begin with speech delays and progress to the loss of communication skills. Symptoms can be temporary or permanent depending on the damage.

LKS can be difficult to diagnose because its symptoms are similar to many other neurological disorders, such as autism and mental retardation.

Is there any treatment?

In some instances, an individual will completely recover from aphasia without treatment.In most cases language therapy should start as soon as possible and be tailored to the individual needs of the patient.

Rehabilitation with a speech pathologist involves:

Exercises in readingExercises in writingExercises in following directionsRepetitions of what they hearComputer-aided therapy