4 - Hearing & Speech Development Flashcards
when in gestation does the structure of the ear develop?
20 weeks gestation
at how many weeks gestation is there a functional auditory system?
25 weeks
how does the auditory system develop from 25 weeks gestation to 5-6 months?
- hair cells of cochlea, axons of auditory nerve, neurons of temporal lobe are tuned to receive signals of specific frequencies and intensities
unlike the visual system, what does the auditory system require?
- outside auditory stimulation
- speech, music, meaningful sounds from the environment
how large is the tympanic membrane?
8 x 10mm diameter
what is the organ of hearing?
the cochlea
what is the weakest quadrant of the tympanic membraen?
posterosuperior quadrant
what CN runs through the middle ear?
facial nerve (CN VII)
what are the 4 main roles of the middle ear?
- conduction
- protection
- transducer
- amplifier
why is the middle ear a conducter?
conducts sound from the outer ear to the inner ear
why is the middle ear a transducer?
- converts acoustic energy to mechanical energy
- converts mechanical energy to hydraulic energy
without middle ear function, how much acoustic energy in the air would be transmitted to inner ear fluid?
1/1000
which part of the cochlea can hear the highest frequency sound? which can hear the lowest?
highest - base
lowest - apex
why do different regions of the cochlear hear different frequencies of sounds?
the basilar membrane has different levels of stiffness at different points, so it creates a different response when fluid hits it.
which area is responsible for speech comprehension?
wernicke’s area
which are is responsible for production of speech?
broca’s area
consonants are often high/low in frequency?
high
what is the hearing threshold level for normal hearing?
<20dB
what is the hearing threshold level for mild hearing loss?
20-40dB
what is the hearing threshold level for moderate hearing loss?
40-70dB
what is the hearing threshold level for severe hearing loss?
70-90dB
what is the hearing threshold level for profound hearing loss?
> 90dB
how do you test the hearing of children 6-24 months?
visual reinforcement audiometry
how do you test hte hearing of children >24 months?
conditioned play audiometry
how do you test the hearing of a child >36 months?
conventional audiometry
how do you test the hearing of a child <6 months?
objective measures such as OAE or ABR
what is visual reinforcement audiometry?
- tester puts toy in front of child + child focuses attention on it
- sound produced to side
- hearing - child turns to sound + positively reinforced by seeing another light up toy
- conditions child
- can establish what level child can hear
what is an issue with visual reinforcement audiometry?
free field testing - not ear specific
what is conditioned play audiometry?
child is conditioned to perform a task when they hear a sound
what is good about conventional audiometry?
it is ear specific
what does speech audiometry test?
ability to recognise and understand speech
what does the speech discrimination assessment measure?
functional hearing ability
how do otoacoustic emissions work?
- small probe placed in ear
- creates sound
- sound stimulates the cochlea
- outer hair cells vibrate
- produces nearly inaudible sound that echoes back into middle ear
- the sound that echoes back is measured
how are otoacoustic emissions graded?
pass/fail response
what happens if a baby fails OAE?
- indicates need for more testing
- could be hearing loss, ear wax, fluid, infection, malformed middle ear
how are auditory brainstem responses performed?
- electrodes placed on skin of head and connected to a computer
- records brain wave activity in response to sounds through earphones
- tests how cochlea and brain pathways work
list the 5 nerves involved in the auditory pathway:
E - 8th nerve
C - cochlear nucleus
O - superior olivary nucleus
L - lateral lemniscus
I - inferior colliculus
what is the difference between speech and language?
speech - the way we say something
language - form, meaning and use of words and utterance
what is neuroplasticity?
brains ability to change through experience
describe the different stages of language development
- <6 months - pre-verbal
- 6-10 months - babbling
- 6-12 months - detect phonemes
- 1 year - one word morphemes
- 18 months- two word phrases
- 2.5 years - simple sentences that lack tenses and have errors in syntax
- pre school - improve phonemes, pronunciation and articulation
- primary school - master syllable stress
what can be the outcome if a child fails to get support as a language learner in early childhood?
- aggressive behaviours
- withdrawn into silence
- reading and educational difficulties
what two categories of deaf people benefit from cochlear implants?
- pre-lingually deaf children - encourages auditory input
- post-lingually deaf adults - have sound memory and speech is developed
when should pre-lingually deaf children be prescribed hearing aids? when should they have a CI?
- hearing aids before 3 months
- implants before age 4, ideally at 12 months
after what period does CI not improve hearing or speech?
after the period of neuroplasticity
