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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Evidence for localization: aphasia
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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Evidence for localization: aphasia
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)