Hearing Science Terms & Definitions | Lecture 7 Study Guide

hydraulic

mechanical

chemo-electrical

what are the three modes of cochlear physiology?

1. begins with mechanical stimulation--stapedial footplate at the oval window

2 mechanical energy is transduced into hydraulic motion of the perilymph--made possible by the polarization effect

3. hydraulic action in the bony labyrinth mechanically causes motion of the edolymph which stimulaties corti's organ--soft tissue is displaced by wave motion

4. the motion of the sensory cells creates chemo-electrical response

how do sound waves travel through the cochlea?

explain the cochlear physiology

Georg von Bekesy

who was the first person to study the function of the auditory organ experimentally... took theoretical considerations and used empirical evidence to make conclusions?

George von Bekesy

-won Nobel prize in medicine for discoveries about cochlear mechanics

-first to study the function of the auditory organ (cochlea) experimentally, replacing theoretical consideration with empirical evidence

George von Bekesy

-conducted research on the temporal bones

-discovered the traveling wave in the cochlea

1. deflecting of the basilar membrane

2. height of discplacement/ deflection

3. point of maximal displacement is frequency specific

4. frequency specifity is a passive feature

what were georg von beskeys four observations based on the traveling wave of the cochlea

base to apex

the hydraulic motion in one direction from ________ to __________

as the stapes stimulates the perilymph at the oval window the basilar membrane pushes downward by the pressure of the hydraulic wave

-hydraulic motion travels from base to apex (one-way direction)

what was observed to determine the defleciton of the basilar membrane?

height of the displacement gradually increases as the wave travels to the apex. this is die to the close match between the frequency of the wave's vibrations and the resonance characteristics of the basilar membrane

-the traveling wave reaches maximum amplitude, then it quickly dimenishes

what was observed to determine the height of displacement/deflection

-it occurs at the place where the frequency of the wave matches the resonant characterisitcs of the basilar membrane

-basilar membrane acts as a series of passband filters

what was observed to determine the point of maximal displacement is frequency specific?

basal

the highest frequencies are at the ________ end

apical

the lowest frequencies are at the _________end

gets wider and loses stiffness from base to apex

what happens to the basilar membrane from base to apex?

due to a gradient change in stiffness of the basilar membrane from base to apex

what was observed to determine that frequency specifity is a passive feature?

hydro-mechanical energy in the cochlea

mechanical vibrations of the ossicular chain are transformed into what?

hydro- fluid in the cochlea

mechanical- motion of the structures of the cochlea

what does the word hydro-mechanical mean when referring to the cochlea?

frequency specific

maximum displacement of the basilar membrane is _______

later

low frequency sounds are detected _________than high frequency sounds

because of the incompressible nature of the fluid-filled cochlea

how come when the stapes moves back and forth in all locations along the basilar membrane recieves the same vibrational input at the same time?

-it moves in response to an applied force, the narrower and stiffer base will always vibrate before the wider and less stif apex----this is because there is less inertia (less mass) to overcome at the base

why does the traveling wave of the cochlea always travel from base to apex?

the amplitude is relatively low at the base and grows to its peak at the stimulus frequency location, then decays rapidly

explain how the amplitude (amount of displacement) grows and decays in the traveling wave of the cochlea?

the excitory phase of the hair cells

when the steorcilia bends towards the tallest row (away from the modilus) this triggers the ______________, this occurs when the basilar membrane moves toward the scala vestibuli

not travel very far

will travel further

if the sound has a high frequency content the wave will ___________ if the sound has a low frequency content it will __________________

due to the increasing resistance caused by an increasing impedence mismatch

why doesnt the traveling wave go beyond the location of "best resonance"?

-observation of basilar membrane motion at a specific frequency location/region

-psychological tuning curve

-Psychoachoustic tuning curve

types of tuning curves

psychological tuning curve

observing of firing of a specific afferent neuron (frequency specific)

psychological tuning curve

lowest level of sound to signal firing rate

-measure range of frequencies that produce a criterion increase in the discharge rate for a particular neur

psychoacoustic tuning curve

observation of the stimulus levels and frequencies required to mask a probe tone

psychoacoustic tuning curve

-play a sound at one frequency and then play other varying frequencies over it and determine what the lowest level required to mask the initial sound is

-measuring the range of frequencies that can interfere with (mask) the perception of a target tone near threshold

characteristic frequency

the frequency to which each location on the basilar membrane responds best

tuning curve

a graph of the responses of a single auditory nerve fiber or neuron to sounds that vary in frequency and intensity

hearing test

a tuning curve is not a ___________

1. experimenter picks a frequency

2. experimenter plays the frequency starting at the lower level and then proceded to raise the level until the basilar membrane vibrates

3. repeat this process

4. plot the points on the graph and connect the dots

5. what you then have plotted is the threshold of where the BM vibrates at a certain frequency

how is the y-axis determined for the tuning curve?

thomas gold

English physicist who went to Bekesy in the late 40s to discuss certain attributes of the hearing mechanism:

1) high sensitivity

2) sharp frequency tuning--people could distinguish between slightly different frequencies

3) wide dynamic range of hearing

*From these observations suggested there must be a POSITIVE INNER EAR FEEDBACK MECHANISM

thomas gold

*From these observations suggested there must be a POSITIVE INNER EAR FEEDBACK MECHANISM

upward spread of excitation

where a high level, low frequency tone will cause a higher frequency portion of the BM to vibrate?

OHC

what acts as a cochlear amplifier so it amplifies the motion of the BM?

1. death

2. high level sounds

3. age

4.ototoxcicity

what factors can cause the OHC's to hault function?

tester chooses

where does the value of the x-axis come from?

ear plugs

how to get rid of the upward spread of masking?

upward spread of masking

Masker of a given frequency masks higher-frequency signals more than lower-frequency signals

dip

the CF is represented by the __________ in the tuning curve

shape of the filter (shape of the tuning curve)

frequency selectivity or tuning

the combination of the frequencies and the intensities that produce a response (vibration) for a particular location on the BM provide an estimate of the _________________ associated witht that location: this is termed _____________________

frequency selectivity

the auditory system's ability to respond differentially to different frequencies and bands of frequencies

physiological or neural tuning curves

what tuning curve is obtained by measuring the range of frequencies that produce the criterion increase in the discharge rate for a particular motion?

psychoacoustic tuning curve

what tuning curve is obtained by measuring the range of frequencies that can interfere with (or mask) the perception of a target tone near the threshold

tuning was much broader

bekesy measured the tuning of the BM in human cadavers and found that ___________________ than the tuning curves measured from individual auditory nerve fibers of the 8th nerve in living animals or in psychoacoustic experiments

passive process in the cochlea

-broad tuning curve of the BM was related tot he traveling wave that ocurs becuase of the width and stiffness of the BM

active process in the cochlea

a relatively sharp BM tunign is dependent on ________________

-only seen in a healthy normal cochlea

character frequency

each location along the bm responds best to a specific frequency called the _____________

motility

active process is due to the __________of the OHCs

sharp frequency tuning

gold concluded that some active energy process would be needed in the cochlea in order to have_________________

active feedback loop

what generates vibratory energy in the cochlea

active feedback loop

cold determined that the active energy process would include___________

Kemp

who discovred the phenomenon of otoacoustic emissions (OAEs)

OHCs

OAE instruments are used today to determine the funciton of ______________________

active cochlear process

kemp postulated that these emissions are from some _____________that generates additional mechanical on the BM

middle ear

the energy generated by the active cochlear process can travel back out through the _____________and can generate very low level acoustic sounds in the ear canal

william brownell

discovered hair cell motility

electrical currents

what causes OHC motility?

stimulating position

at low to moderate sound pressure levels the motion of the BM is not sufficient to make the sterocilia of the IHCs move to the ___________________

amplifies the displacement of the BM through the motility of the OHCS

what is the function of the active cochlear process of the OHCs?

cochlear amplifier

Outer hair cells, including the motor proteins in the outer hair cell membrane, that amplify displacements of the basilar membrane in the cochlea

cochlear amplifier

OHCs are also called __________

active process in the cochlea

when damage to the OHCs occus the __________________is damaged often resulting in mild hearing loss

OHCs

middle ear or

outer ear

absense of OAEs suggests some abnormality in auditory function either in the _______________________________

background noise

Zhao and Stephens found that for individuals with normal audiograms, OHCs appear to be related to a decreased ablity to recognize speech in the presence of _______________