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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 • • • • • 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 • • Sensorineural hearing loss can be caused by – – – – – 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: – – – – – 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 – electrodes implanted in cochlea to stimulate auditory nerve – microphone in a BTE hearing aid connected to sound processor which translates microphone signal into electrical signals • • – – 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 • • • • 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 – – – – 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 – – – – – 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 – – – – 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