Neurolinguistics and Language Acquisition

7/28/2019 Neurolinguistics and Language Acquisition

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Neurolinguistics Goals:

By the end of this section you should beable to:

identify the main language centers of thebrain

describe effects of injuries to languagecenters

explain how certain types of specific braindamage provide evidence about howlanguage is processed in the brain


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Neurolinguistics: the branch of linguistics concerned with thebiological and neural foundations of language.

Modularity: brain isstructured and subdivided into specific

areas that control particular faculties.

Aphasia: a specificlanguage disorder following brain lesionscaused by stroke, tumor, gunshot wounds, or severe

infections.

Lesion: A circumscribed pathological alteration of braintissue. (appears as a scar on the brain)

Definitions


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Neurolinguistics

Neurolinguists investigate

How the brain processes language

Where the brain processes language

Who neurolinguists study

Normal subjects

Abnormal subjects

patients with brain injury (e.g. stroke)

patients who have had brain surgery


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The part of the brain with greatest mass is

called the cerebrum.

the cerebrum is made up of two hemispheres,

the left and right hemispheres

which are connected by nerve fibers called the

corpus callosum

Brain structure


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Right hemisphere specialties

Holistic, spatial processing

pattern-matching (e.g. recognizing faces)

spatial relations

emotional reactions

music (processing by musically naive

individuals)linguistic intonation (but not lexical tone!)


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Left hemisphere specialties

Sequential processing

rhythm temporal, relations, analyticalthinking, music (processed by musically

sophisticated individuals), mathematics,intellectual reasoning

language, speech sounds

especially so for adult, male, right-handed, literate, monolingual subjects


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Language:left hemisphere

Evidence: dichotic listening experimentsThai tonal contrasts

[na@] aunt (high) [na^] face(falling)

[na#] field (mid) [na&] thick (rising)[na$] (nickname) (low)

Thai speakers process tone with lefthemisphere

English speakers presented with tonalcontrasts process tone with righthemisphere


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Language:left hemisphere

Evidence from split-brain patients

Severe cases of epilepsy treated by

severing corpus callosum

Task of naming object held in left hand(right brain)

left eye open (right brain), right eye covered

much harder than

right eye open (left brain), left eye covered


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corpus

callosum

(connectshemispheres)


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Lateralization: Caveats

Lesser left hemisphere specialization for

language if:

left-handed

female

illiterate

multilingual


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Modality and lateralization

No effect of language modality on

lateralization for language

Left hemisphere specialization forlanguage even for signed languages


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QuickTime an d a

Cinepak decompressorare needed to see this picture.

language centers (left hemisphere)

Brocas

Wernickes

Arcuate

fasciculus


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Broca's area lesions result in Broca's aphasia (a.k.a.expressive aphasia, motor aphasia)

Characteristics of Brocas aphasia

basic message of meaning clear but

speech is not fluent

phrases are telegraphic (absence of function words)

incorrect production of sounds

Cinderella, as told by a Brocas aphasic

Cinderella...poor...um dopted her...scrubbed floor, um,tidy...poor, um...dopted...si-sisters and mother...ball.Ball, prince um...shoe.

Evidence for localization: aphasia


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Wernickes area lesions

Characteristics of Wernickes aphasia

speech is fluent, but

often nonsensical or circuitousDescription of a knife by a Wernickes aphasic

Thats a resh. Sometimes I get one around here that Ican cut a couple regs. Theres no rugs around here and

nothing cut right. But thats a rug and I had some nicerekebz. I wish I had one now. Say how Wishi idaw, uh

windy, look how windy. Its really window isnt it?


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Lesions at arcuate fasciculus (subcortexnerve fibers connecting Brocas, Wernickesareas)

Conductive/conduction aphasia

Characteristicsusually good comprehension, fluent speech but

difficulty repeating

difficulty reading out loud

difficulty writing


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DISORDERS OF SPEECH: APHASIAS

Approximate left hemisphere area where acute

lesions almost always produce language

disorders


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Aphasia is caused by a brain injury, which may occur during a

traumatic accident or when the brain is deprived of oxygen during

a stroke. It may also be caused by abrain tumor, a disease such as

Alzheimer's, or an infection, like encephalitis. Aphasia may be

temporary or permanent.
http://www.ehendrick.org/healthy/001288.htmhttp://www.ehendrick.org/healthy/000226.htmhttp://www.ehendrick.org/healthy/000226.htmhttp://www.ehendrick.org/healthy/001288.htm


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Study of brain damaged patients

Paul Broca 18241880

Damage in Brocas area

- Problems in production:

articulation, poor use of

grammatical features

- Understanding of speech

fairly normal


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Carl Wernicke 18481904

Damage in Wernickes area

- Prosody and pronunciation

intact, speech is fluent but

empty, but a lot of different

word distortions and difficulties

finding the right word

- Severe comprehension deficits


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The classical view of language in the brain

- Two language centres, for production and comprehensionrespectively: Brocas and Wernickes area.

- The arcuate fasciculus: a bundle of nerve fibers connecting

Wernickes area to Brocas,

is essential for normallanguage function. Damage

to it causes conduction

aphasia:

speech fluent, auditorycomprehension relatively

good, butrepetition of heard

words is impaired.


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Samples of spontaneous speech:

"Yes ... Monday ... Dad, and Paul ... hospital, and ... Wednesday,

Wednesday, nine o'clock and ... Thursday, ten o'clock ... doctors,two, two ... doctors and ... teeth, yah. And a doctor ... girl, and gums,

and I."

"Me ... build-ing ... chairs, no, no cab-in-ets. One, saw ... then, cutting

wood ... working ..."

Performance profile- Production difficulty: slow speech, articulation difficulties

- Little intonation present (dysprosody)

- Often agrammatism: 1) sentence construction deficit,

2) possibly selective impairment of grammaticalelements, or

3) difficulty in understanding syntactically

complex sentences.

- Comprehension relatively good

Non-fluent aphasia

Brocas aphasia


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The brain of a patient who suffered from Wernickes

aphasia due to a stroke in the left middle cerebral artery

W i k h i


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A sample of conversational speech

Examiner: What kind of work have you done?

Patient: We, the kids, all of us, and I, we were working for a long timein the ... you know ... it's the kind of space, I mean place rear to the

spedawn ...

Examiner: Excuse me, but I wanted to know what work you have

been doing.

Patient: If you had said that, we had said that, poomer, near thefortunate, porpunate, tamppoo, all around the fourth of martz. Oh, I

get all confused.

Performance profile

- fluent but meaningless speech

- auditory comprehension deficit

- word-finding difficulties, word substitutions and made-up

words

- normal prosody, syntactic processing relatively normal

Wernickes aphasia

C d ti h i


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Conduction aphasia

Example of conduction aphasics

repetition performance:

BEDbed PRESIDENT

peh-tn HIPPOPOTAMUS?

Performance profile

- Repetition disproportionately severely

impaired, speech fluent and auditory

comprehension relatively good

- Word-finding difficulties, sometimes semantic

difficulties

- Outstanding difficulty is in the proper choice

and sequencing of phonemes in speech output,

leading to numerous phonological errors


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Other types of aphasias

- Global aphasia: wide-spread left-hemisphere damage, all basiclanguage functions are affected, some more than others.

- Anomic aphasia:primarily influences an individual's ability to findthe right name for a person or object. As a result, an object may

be described rather than named. Often results from damage in

inferior temporal areas.

Some less common types of aphasias:

- Transcortical sensory aphasia

- Transcortical motor aphasia

- Subcortical aphasia

- Crossed aphasia


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Clinical characterizations of aphasic syndromes

Fluency of Language Repetition Name of

Output Comprehension Aphasic Syndrome

-----------------------------------------------------------------------------------------

Bad Good Moderate BROCA

Good Bad Bad WERNICKE

Good Good Bad CONDUCTION

Bad Good Good TRANSCORT.MOTOR

Good Bad Good TRANSCORT.SENSORY

Bad Bad Bad GLOBAL

--------------------------------------------------------------------------------------------------------------


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Neurolinguistics summary

Hemispheres of brain have differentspecialties, including language (most clearlyfor right-handed (etc.) individuals)

Lateralization is not affected by languagemodality

Language centers within the brain: Broca's,

Wernicke's areas especially importantNeurolinguistics provides evidence for humanspecialization for language


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Acquisition Goals:

By the end of this section you should beable to:

explain what is meant by innateness oflanguage

identify the major milestones of 1stlanguage acquisition

describe major similarities and differencesbetween 1st and 2nd language acquisition


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Innateness hypothesisInnateness (Lennenberg)

humans are genetically predisposed to aquirelinguistic competence (though not in any specificlanguage)

humans are born with the knowledge thatlanguage has systematic and unique patterns

humans are born with the critical abilities that

enable them to learn linguistic patternspatterns that are common to language ingeneral are considered parts of universalgrammar


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Innateness hypothesis

charactistics of innate behaviorinnately determined behavior is common,especially in species specific communication

emerges before its necessary

emergence not triggered by specific event

little effect of direct teaching and overt practice

regular sequence of milestones correlated with

maturationcritical period after which behavior cannot beadequately acquired (note difference betweenbabies and adults learning a language)

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Neurolinguistics and Language Acquisition