4 - hearing and speech development lecture Flashcards
outline the embryology of the ear
- structure of ear and neurosensory - 20 weeks gestation
- 25 weeks - functional auditory system
- 25 weeks gestation to 5-6 months - hear cells of the cochlea, axons of the auditory nerve, and the neurons of the temporal lobe auditory cortex are tuned to receive signals of specific frequencies and intensities
what does the auditory system require, unlike the visual system?
outside auditory stimulation — speech, music, meaningful sounds from the environment
what is the organ of hearing?
cochlea
label this tympanic membrane
what forms the medial wall of the middle ear?
cochlea/cochlear promontory
describe the chorda tympani
- runs in middle ear
- branch of facial nerve
- innervates taste to the anterior 2/3 of the tongue
what are the roles of the middle ear?
- conduction — conducts sound from the outer ear to the inner ear
- protection — creates a barrier to protect middle and inner ear structures from foreign bodies
- transducer — converts acoustic to mechanical energy and mechanical to hydraulic energy
- amplifier — transformer action of middle ear
only about 1/1000 of the acoustic energy in air would be transmitted to the inner ear fluid (30dB loss) without middle ear function — seen in glue ear
where is the inner ear?
petrous part of temporal bone
what is the inner ear made up of?
cochlea and vestibular system
utricle and saccule vs semicircular canals
vestibule — aids in balance when stable/not moving
semicircular canals — aids in balance with movement
what semicircular canals are there?
posterior/inferior, lateral and anterior/superior
how many turns are there in the cochlea?
2.5
label this cochlea
what separates the vestibule from the middle ear?
oval window
what does the membranous labyrinth consist of?
cochlear duct, semicircular ducts and utricle and saccule
what is the membranous labyrinth filled with?
endolymph
what does the bony labyrinth consist of?
cochlea, vestibule, 3 semi circular canals
what propagates sound waves from the base?
cochlea
the scala vestibuli and scala tympani are _____ filled chambers
perilymph
inner vs outer hair cells in terms of Reissner’s membrane
- hair on IHCs does not touch the membrane
- hair on OHCs are embedded into this membrane
what channel ends at the round window?
scala tympani
what channel is located inferiorly to the cochlear duct?
scala tympani
what channel is continuous with the vestibule?
scala vestibuli
another name for Reissner’s membrane?
vestibular membrane
what does movement of the tympanic membrane in response to impulses from the external ear cause?
vibration of ossicles — mechanical energy
describe the tonotopic arrangement of the inner ear
- hair cells are arranged along the basilar membrane according to what frequencies they pick up
- base — higher frequencies picked up
- apex — lower frequencies picked up
briefly outline the auditory pathway from the cochlear nucleus
cochlear nucleus —> superior olivary nucleus —> inferior colliculus —> medial geniculate nucleus —> auditory cortex
wernicke’s vs broca’s area
wernicke’s area — temporal lobe — speech comprehension
broca’s area — frontal lobe — production of speech
how do you test children’s hearing?
- 6-24 months — visual reinforcement audiometry
- > 24 months — conditioned play audiometry
- > 36 months — conventional audiometry
- <6 months — objective measures
describe visual reinforcement audiometry
- 6-24 months
- child needs to be able to independently turn their head
- toy used to keep attention and focus
- sound made to the side
- +ve reinforcement (eg. toy lights up)
- free-field testing — not ear specific
describe conditioned play audiometry
- > 24 months
- conditioned to perform task when sound plays
- ear specific
describe conventional audiometry
- > 36 months — may be more if child is not mature enough
- patient presses button when they hear a noise
- ear specific
describe speech audiometry
- tests the ability to recognise and understand speech
- speech discrimination assessment measures functional hearing ability
- hearing in noise test (HINT), speech recognition in noise test (SPRINT), words in noise test (WINT) — background noise
describe the newborn hearing screening program
- all newborns
- automated otoacoustic emissions +/- auditory brainstem responses (ABR)
- high failure rate in 1st 24 hours
- can be hard in a noisy setting
- have 2nd OAE if failed. if failed again —> ABR
describe ABR
- assesses brain’s response to sound
- amplitude = no. of neurons firing
- latency = speed of transmission
speech vs language
- speech is the way we say something
- language is the form, meaning and use of words and utterance
what is neuroplasticity?
the brain’s ability to change through experience
speech under 6 months
PRE-VERBAL
- crying, gestures (to get attention)
- hungry, tired, cold, hot, pain
- 2 months : coos and gurgles
- 3 months : fixes on sound
- calms to familiar voices
speech 6-10 months
BABBLING
- 6 months : able to express pleasure and displeasure
- child can distinguish sounds of any language and reproduce this (lost by age 1)
- communicates by sounds and intonations
speech 6-12 months
- begin by detecting very small differences between speech sounds (phenomes)
- at 6 months they can contrast different vowel phenomes eg. a & i
- by 11-12 months they can recognise consonants
- as they get older they learn to ignore other non specific sounds
speech at 1 year
- one word stage — mainly morphemes
- end of 1st year — should understand about 50 words, say about 5
- one word to describe actions - “ball” = “get the ball” - semantics (understanding) develops before word
- learn words which produce effects - “again” “more”
speech at 18 months
= two word phrases
- should have about 20-50 words
- naming
- demanding
- questioning
speech at 2.5 years
- simple sentences
- lacks tenses
- errors in syntax (order of words wrong)
- recognition of rhyme and intonation
- 200-300 words
speech in preschool 2.5-5 years
- improvement in phenomes
- development of pronunciation and articulation
speech in primary school 6-10 years
master syllable stress to distinguish between similar words
what are some of the lifelong consequences someone can face if as a child they fail to get support as a language learner?
- aggressive behaviours
- withdrawn into silence
- reading and educational difficulties
language affects both cognitive growth and social competence!
what are the advantages and disadvantages of multi-lingual children?
advantages:
- greater cognitive flexibility
- better perceptual skills
- divergent thinkers
- better understanding of syntax and language
- delay in dementia onset by almost 5 years
disadvantages:
- smaller vocabulary than peers
- delays in general learning milestones eg. maths and reading in primary school years
who benefits from a cochlear implant?
—> pre-lingually deaf children — prescribe hearing aids before age 3 months. implant before age 4 years, ideally at 12 months
—> post lingually deafened adults — have sound memory. have used hearing aids to optimise hearing. already know how to speak and use language
cochlear implantation does not improve hearing or speech after what period?
the period of neuroplasticity — pathway lost
