Auditory Flashcards
audiogram
sound “area” of hearing
smallest bone in the body
stapes
smallest muscle in the body
stapedius
reference pressure
corresponds to threshold; lowest sound pressure normal hearing adults can detect
presbycusis
high frequency hearing loss with aging
severe hearing loss
~45dB
spectrum
pattern of sound frequency
3 parts of ear
outer ear, middle ear, inner ear
outer ear
pinna – like a funnel; amplifies the sound
middle ear
- deep to tympanic membrane
- contains 3 ossicles
- muscles: stapedius and tensor tympanii
goal of middle ear
- overcome “problem”
- cochlea filled with fluid
Impedence mismatch
g
conductive loss
- mechanical type of hearing loss
- many subtypes
- example: otitis media with inclusion; obstruction of canal with mass and limits motion of tympanic membrane
Perilymph
high Na, low K; in Scala vestibule and scala tympani
Endolymph
High K+, low Na; in scala media
Endocochlear potential
powers transduction of sound energy into electrical activity
congenital hearing loss
due to collapse of endocochlear potential
characteristic frequency
frequency at which threshold the lowest
Intensity
encoded by rate at which auditory nerve fibers fire APs
- louder sound – more action potentials
auditory neuropathy
problem with transmission of info from hair cells to auditory nerve
- pts present with normal or near-normal audiogram and OAEs but abnormal or absent Auditory brainstem responses (ABRs)
- have difficulty with speech and temporal processing)
Prosthetic devices
hearing aid, middle ear implant, cochlear implant, bone-anchored hearing aid
middle ear implant
- transducers that vibrate vesicular chain
- implanted in ear
cochlear implant
- bypass acoustic conductive apparatus of external//inner ear
- stimulate electrically by array of electric contacts implanted into cochlea
- trying to stimulate auditory nerve fiber using htis principle
3 main acoustical cues to location
interaural time delay (ITD), interaural level of differences (ILD), spectral cues (>5kHz)
Duplex theory of sound
Low frequencies- ITDs
High frequencies - ILDs
Tonotopic organization
as nerve fibers preserve topographic mapping of sound frequency in all neural structures so that adjacent neurons sensitive to slightly different adjacent sound frequencies
parallel processing
one common input separated into pieces
- starts in cochlear nucleus
Subnuclei of cochlear nucleus
Dorsal Cochlear Nucleus, anteroventral cochlear nucleus, posterovenral cochlear nucleus
Coincidence model in the Medial Superior Olive (Jeffress model)
afferent projections keeping track of timing, delay lines created by different lengths of axons projecting to medial superior olive, neurons with property of coincidence detection
- acoustic timing delay if sound from one side
- only occurs in low frequencies less than 1500 Hz
Auditory part of thalamus
medial geniculate
primary cortex is in which Broadmann area?
41
Wernicke’s area
important for speech comprehension; in Secondary auditory cortex
Broca’s area
Broadmann’s area 44/45; if problem with this area, can understand but not produce speech?
