Transcript chapter 9

CHAPTER 9
Hearing and Language
Hearing loss
Hearing loss
• Three kinds of hearing loss
– conductive loss
– sensorineural loss
– mixed
Conductive Loss
• Occurs when sound is not conducted
efficiently through
– the outer ear canal to
– the eardrum and ossicles of the middle ear.
• Conductive hearing loss usually involves
– reduction in sound level,
– Lose the ability to hear faint sounds.
• This type of hearing loss can often be
medically or surgically corrected.
Conductive Loss
• Examples of conditions that may cause a conductive hearing loss
include:
– Conditions associated with middle ear pathology
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fluid in the middle ear from colds, allergies
otitis media
poor eustachian tube function,
perforated eardrum
benign tumors
– Impacted earwax (cerumen)
– Infection in the ear canal (external otitis)
– Presence of a foreign body
– Ossification of the ossicle chain (otosclerosis)
– Absence or malformation of the outer ear, ear canal, or middle ear
Sensorineural and Mixed loss
• Sensorineural loss
– occurs when there is damage to the inner ear
(cochlea) or to the nerve pathways from the inner ear
(retrocochlear) to the brain.
– Sensorineural hearing loss cannot be medically or
surgically corrected. It is a permanent loss.
• Sensorineural hearing loss involves both
– a reduction in sound level, or ability to hear faint
sounds,
– speech understanding, or ability to hear clearly.
Sensorineural and Mixed loss
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• Sensorineural hearing loss can be caused by
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Diseases and tumors, viruses
birth injury, head trauma
drugs that are toxic to the auditory system, and
genetic syndromes.
noise exposure
• Mixed loss
– conductive hearing loss in combination with a
sensorineural hearing loss.
– damage to outer or middle ear and
– the inner ear (cochlea) or auditory nerve.
What does hearing loss sound like?
• Degree of hearing loss refers to the severity of the loss.
– five broad categories that are typically used.
– Numbers representative of the patient's thresholds
– softest intensity that sound is perceived:
• Range of hearing loss:
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Normal range or no impairment = 0 dB to 20 dB
Mild loss = 20 dB to 40 dB
Moderate loss = 40 dB to 60 dB
Severe loss = 60 dB to 80 dB
Profound loss = 80 dB or moreMild loss
• Also Tinnitus
• What does hearing loss sound like? http://www.hearit.org/forside.dsp?forside=yes&area=244
Treating Hearing Loss
• Hearing aids
– analog: just make sounds louder
– digital: programmed to increase loudness of
specific range of sounds
• Several kinds:
– behind the ear: BTE
– ear canal: large and small
– Bone anchored heairng aid (BAHA)
Treating Hearing Loss
• Cochlear implants:
– use for sensory/neural loss: for people lost ability to translate
sound into electrical signals to brain
– Loss is due to hair cell damage in basilar membrane:
• Cochlear implants bypass external/middle ears
and just stimulate inner ear
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electrodes implanted in cochlea to stimulate auditory nerve
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microphone in a BTE hearing aid connected to sound processor
which translates microphone signal into electrical signals
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These signals directed to auditory nerve via electrode array
implanted in cochlea
About 16-22 “channels” for 120-240 inputs
Elicit patterns of nerve activity that brain interprets as sound
Not completely “normal”- but close enough
CHAPTER 9
Hearing and Language
Language
Language
• Is this just a human behavior?
• Language = extremely complex perceptual ability
– not limited to speech
– includes the generation and understanding of
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Written
Spoken
Gestural communication.
Non verbal communication
• Expressive vs. receptive language:
– Expressive: spoken and written produced language
– Receptive: ability to receive or understand spoken and written
language
Language production
aphasias
• Aphasia = brain problem, not “hearing” problem
• Aphasia:
– In 1861 the French physician Paul Broca first reported aphasia
– language impairment caused by damage to the brain
– results from damage to the frontal area anterior to the motor
cortex, now known as Broca’s area.
• Broca’s aphasia:
– language impairment caused by damage to Broca’s area and
surrounding cortical and subcortical areas.
– It is also referred to as expressive aphasia.
– Unable to produce clear language
Receptive Language
aphasia
• Nine years after Wernicke’s work: German doctor named
Carl Wernicke identified a second site
– damage produced a different form of aphasia- more with
“understanding”
– located in the posterior portion of the left temporal lobe, now
known as Wernicke’s area.
• Wernicke’s aphasia:
– the person has difficulty understanding and producing spoken and
written language.
– Often called receptive aphasia
– term is misleading: Same problems with understanding language
also show up when producing it.
– If can’t understand, then can’t produce!
Dyslexia, Alexia and
Agraphia:
• Alexia: inability to read.
• Agraphia: inability to write.
• Are aphasias, in that are disruption of language
• Presumably due to disruption of pathways in the
angular gyrus of the temporal lobe
– connect the visual projection area with the auditory and
visual association areas in the temporal and parietal
lobes.
– Results in inability to integrate two perceptual
activities
Dyslexia, Alexia and
Agraphia:
• Dyslexia: used as a GENERAL term for a learning disorder, but
incorrect
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Dyslexia impairment of reading
Dysgraphia: difficulty in writing
Dyscalculia: disability with arithmetic.
Dyslexia can be acquired, but it is more often developmental.
• In most people the planum temporale, where Wernicke’s area is
located, is larger in the left than in the right.
– in dyslexics, it is more frequently equal in size or larger on the right.
– Suggests that language area is not sufficiently developed, or developed
differently
• Also: may be due to problems in Basal ganglia and Cerebellum
– Problem with inhibiting inappropriate behaviors while engaging in
academic behavior
– Can’t walk and chew gum and read at same time!
How Diagnosis Language
Disorders?
• Rasmussen and Milner (1977) used the Wada technique
– involves anesthetizing one hemisphere at a time by
injecting a drug into each carotid artery;
– when the injection is into the language-dominant
hemisphere, language is impaired.
– Risky to say the least!
• Also used electrical stimulation to produce similar effects
• Alternative: determined location of language control in
seizure patients before removing lesioned tissue that was
causing epileptic seizures.
Right Hemisphere: ALSO
important for Language
• Prosody : important right hemisphere language function!
– use of intonation, emphasis and rhythm to convey meaning
in speech.
– Most obvious right-hemisphere role in language
• The right hemisphere : Important in understanding
information from language that is NOT specifically
communicated by word meaning
– E.g., when the meaning must be inferred from an entire
discourse or when the meaning is figurative rather than
literal.
– Think of idioms; sarcasm, intonation and inflection
– Very difficult: must compare words to tone
What if damage the left
hemisphere?
• Severe damage to left hemisphere = severe disruption in
language
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Extent of damage depends on age
Younger = more flexibility
Before 3:can recover most, if not all abilities
Before 12: can recover many abilities
Age 12 or older: more difficult and less successful recovery
• The right hemisphere can take over language functions
following left-hemisphere damage
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As long as the injury occurs early in life
Good results below age 6; okay results pre-puberty
Hemispherectomy patients
https://www.youtube.com/watch?v=7zBrY77mBNg&list=PLjx0
NOT_kNrKoguxJ9DXwCLyb6AF8OSsj&index=3
Why Language?
• Darwin:
– suggested we have an instinctive tendency to speak
– What mean?
• infants seem very ready to engage in language
• Language learning is innate
• learn with minimal instruction.
• Noam Chomsky (1980) and later Steven Pinker (1994):
– interpreted children’s readiness to learn language as evidence of
a language acquisition device
– part of the brain hypothesized to be dedicated to learning and
controlling language.
Language
• Is nurture not important?
– Not all researchers agree with innate language theory
– E.g., Skinner
– Most accept that there are biological reasons why language
acquisition is so easy.
• Why ease of children’s language acquisition?
– Due to a brain-based sensitivity to rhythmic language patterns
– Sensitivity does not depend of the form of language.
– Whatever language you are exposed to, your brain becomes
“tuned” to
– Think about in terms of cochlear implants!
Imitation and Language
• Researchers believe that the ability to imitate gestures
was critical to the development of language in humans.
– Recent evidence: infants who point/gesture learn language
faster
– Baby sign
• Some language theorists may have identified
mechanism for the imitative development of language:
– mirror neurons
– respond both when engage in specific acts and while
observing the same act in others.
Animal Language
• Why study Animal language:
– intrigues us: We want to know whether we have any company “at the
top,”
– trace the evolutionary roots of language.
• The rationale behind animal language research:
– any behavior or brain mechanism we share with genetically related
animals must have originated in those common ancestors.
– Evidence of language in other animals?
• Many animals studied:
– dolphins, elephants, whales, and gorillas
– Major contender for a co-possessor of language has been the chimpanzee
because is closest genetically
• That not necessarily best organism , however,.
Many animals have
rudimentary language
• Examine animal language from animal point of view
• See if can determine syntax, semantics from recordings of ongoing
language
• Good evidence for language in several animals
– Tamarins
– Sea mammals
– Elephants
• Can determine whether other animals share brain organization
associated with human language.
• But remember: Presence of similar brain structures in other animals
does not mean that they use those structures for language.
– Correlation does not equal Causation
– Must proceed with caution