14. Ear ch. 10

amplitude=

Patterns of activity across nerve fibers, The amplitude measures the height of the crest of the wave from the midline. (loudness)

cochlea 1. if uncoiled 2. three parts 3. basilar membrane separates ... 4. Reissner membrane separates.... 5. what is filled with fluid? 6. resting on the basilar membrane is the _____ responsible for auditory transduction

coiled tube within the temporal bone of the head 1. if uncoiled it is a tapered tube 2. three parts: *- vestibular canal* *- cochlear duct* *- tympanic canal* 3. Basilar membrane separates the *tympanic canal and cochlear duct* 4. Reissner membrane separates *vestibular canal and cochlear duct* 5. *Tympanic and vestibular* canals filled with perylimph or fluid 6. resting on the basilar membrane is the *organ of corti* responsible for auditory transduction

Eustachian tube

connects the middle ear with throat, normally closed but can be briefly opened by swallowing or yawning- equalizing pressure between middle ear and outside and allows passage of air

____ and _____ membrane have different anchor points when one moves, the other moves in a different way, creating a sharing force that causes the stereocilia of the ____ ____ to bend. The stereocilia of the ___ ___ bend as they sweep through the endolymph as a result of the movement of the _____ membrane

*basilar and tectoral* membrane have different anchor points when one moves, the other moves in a different way, creating a sharing force that causes the stereocilia of the *outer hair cells* to bend. The stereocilia of the *inner hair cells* bend as they sweep through the endolymph as a result of the movement of the *basilar* membrane

How do the ossicles amplify sound or accommodate for loss of sound between air waves and fluid (cochlear fluid) ? (2 things)

1. *the size difference between tympanic membrane to stapes -> oval window amplifies the forces* 2. they have a lever action so small force applied to the maleus can produce large force on stapes.

1. sound waves are transmitted by vibrations of the tympanic membrane, and the ossicles, 2. into the _____ where they cause pressure waves in the perilymph, resulting in traveling waves in the basilar membrane, which are amplified and sharpened by the effeects of the ____ response in the ____ hair cells 3. The movment of basilar membrane results in ____ ____ on the stereocilia of the __ and ___ hair cells in the _____ ___ ___ ____ 4. ___ ____: the bending of the stereocilia (the motile response going back and amplifying the bacilar membrane) 5. The ___ _____ ___ (type 1 auditory nerve fibers) the bending of hair in ___ ____ ____-> releases neurotransmitters, generating action potentials in ____ ____

1. sound waves are transmitted by vibrations of the tympanic membrane, and the ossicles, 2. into the *cochlea* where they cause pressure waves in the perilymph, resulting in traveling waves in the basilar membrane, which are amplified and sharpened by the effects of the *motile* response in the *outer* hair cells 3. The movment of basilar membrane results in *shearing forces* on the stereocilia of the *inner and outer* hair cells in the *organ of the corti* 4. *Outer hair*: the bending of the stereocilia (the motile response going back and amplifying the bacilar membrane) 5. *The inner hair cells* (type 1 auditory nerve fibers) the bending of hair in *inner hair cells*-> releases neurotransmitters, generating action potentials in *auditory nerve.*

Masking effects consistent with _____ of ______ of traveling wave

Masking effects consistent with *shapes* of *envelopes* of traveling wave

Each location on basilar membrane has a characteristic frequency, near the base of the membrane, responds best to ____ frequency waves, near the apex responds to ____ frequency waves (meaning there is greater ____ at these areas)

Each location on basilar membrane has a characteristic frequency, near the base of the membrane, responds best to *high* frequency waves, near the apex responds to *low* frequency waves (means there is greater *displacement* at these areas).

What type of frequency does temporal code frequency work for?

For low frequencies, timing information is available in addition to place. That is useful because the displacement envelopes are very broad at low frequencies. For high frequencies, only place coding can be used. But the displacement envelopes are very narrow for high frequencies.

How sound waves affect the basilar membrane: 1. pressure waves in air cause vibration of the ____(1)___ 2. vibration of ___(1)___ cause vibration of the __(2)___ 3. vibration of ____(3)____ against the oval window cases pressure wave in the perilymph (aka....) 4. pressure wave in perilymph causes traveling wave in the ___(4)_____ 5. In the middle portion of __(4)__ mid frequency pressure waves cause greatest ____ 6. a thinner, wider, more flexible apex of ____(4)___, low frequency pressure waves cause greatest displacement

How sound waves affect the basilar membrane: 1. pressure waves in air cause vibration of the ____(1)___ 2. vibration of ___(1)___ cause vibration of the __(2)___ 3. vibration of ____(3)____ against the oval window cases pressure wave in the perilymph (aka....) 4. pressure wave in perilymph causes traveling wave in the ___(4)_____ 5. In the middle portion of __(4)__ mid frequency pressure waves cause greatest ____ 6. a thinner, wider, more flexible apex of ____(4)___, low frequency pressure waves cause greatest displacement

Listeners presented with one of six target tones at amplitude just high enough to make the tone easily detectable against a silent background, 1. When the center frequency of a masker is very near the frequency of the target tone the masker threshold is (high/low) 2. that is that the amplitude of the masker has to be _____ decibles greater than the amplitude of target tone to prevent detection of the tone 3. as center frequency of masker gets farther away, the masker must be _____ (louder/quieter) to _____ detection of target tone.

Listeners presented with one of six target tones at amplitude just high enough to make the tone easily detectable against a silent background, 1. When the center frequency of a masker is very near the frequency of the target tone the masker threshold is *low* 2. that is that the amplitude of the masker has to be *just a few* decibles greater than the amplitude of target tone to prevent detection of the tone 3. as center frequency of masker gets farther away, the masker must be *louder* to *prevent* detection of target tone.

There is a density mismatch between what parts of ear? How do the ossicles help this problem?

Outer ear (air) middle ear (air) Inner ear (cochlear fluid) Ossicles help because the area of tympanic membrane is large-> gets translated into a small area on the stapes footplate : the size difference amplifies the forces

Support for place coding: 1. Sharpness of _____ consistent with sharpness of tuning of *________*. 2. Fibers presumably originate from _____ locations along ____ ____.

Support for place coding: 1. Sharpness of *tuning* consistent with sharpness of tuning of *basilar membrane movements*. 2. Fibers presumably originate from *different* locations along *basilar membrane*

Temporal code for frequency 1. _____ ____ can match frequency, within a limited range of low frequencies (up to a few hundred Hz). 2. _____ _____ (phase locking) can extend this range (up to 4000 - 5000 Hz).

Temporal code for frequency 1. *Firing rate* can match frequency, within a limited range of low frequencies (up to a few hundred Hz). 2. *Phase synchronization* (phase locking) can extend this range (up to 4000 - 5000 Hz).

The helicotrema is found in ___. it is an ____ in the partitioning membranes of the apex of the cochlea, providing a _____ pathway for _____ to carry vibrations through cochlea...

The helicotrema is found in *cochlea*. it is an *opening* in the partitioning membranes of the apex of the cochlea, providing a *open* pathway for *fluid* to carry vibrations through cochlea...

The inner hair cells (aka type _ auditory nerve fibers) transmit information about sound to the ...... The outer hair cells (type _ auditory nerve fibers) have another function......

The inner hair cells (aka type *1* auditory nerve fibers) transmit information about sound to the *BRAIN* (transducing them to neural signals) The outer hair cells (type *2* auditory nerve fibers) have another function--> *serve to amplify and sharpen the responses of inner hair cells*

The shearing force on stereocilia in contact with ____ _____ shearing force on stereocilia due to resistance of ______

The shearing force on stereocilia in contact with *tectorial membrane* shearing force on stereocilia due to resistance of *endolymph*

organ of corti

a structure in the cochlea of the inner ear- situated on the basilar membrane; consists of 3 critical points: inner hair cells, outer hair cells, tectorial membrane.

What is shearing force?

basilar and tectorail membrane have different anchor points when one moves, the other moves in a different way, creating a sharing force that causes the tsereocilia of the outer hair (the type 2 auditory nerve) to bend.

Why does the patterns that generate center frequency tuning curves closely resemble frequency tuning curves of auditory nerve fibers?

because listeners perceptual udgements are based on response of type 1 auditory nerve fibers, that is when noise masker has center frequency at or near frequency of target tone, the masker activates type 1 nerve fibers in the region of the basilar membrane with the characteristic frequecny corresponding to frequency of target tone.... but as the center frequency of masker moves away from the target tone (to different frequency hz) then the nerve fibers of that region are freed up to respond to target tone,

what does "displacement of basilar membrane from base to apex over time" mean?

experiment which shows how characteristic frequencies and traveling waves differ over the membrane over time. each location along the basilar membrane has a characteristic frequency, or the frequency to which it responds most readily. -- determines displacement of membrane at that location in response to incoming sounds

frequency=

place and timing/the rate at which something occurs or is repeated over a particular period of time or in a given sample.

Movement of the ____ and ____membrane resulting in a shearing force on the stereocilia

movement of the *basilar and tectoral membrane* resulting in shearing force on *stereocilia*

White noise along with target tone is called...

noise masker

stereocilia are

small hairlike projections on the tops of inner and outer hair cells

why did evolution evolve to have such a complicated and delicate process for ears to include the ossicles?

sound cant be transferred from tympanic membrane to the cochlear fluid -> *the sound vibrations in air have insufficient energy to cause significant vibrations in the fluid*

because the frequency tuning curves of type 1 auditory nerve fibers + the basilar membrane are nearly identical, what does this suggest?

suggest that the tuning of type 1 auditory nerve fibers can be almost entirely accounted for by the frequency tuning of the basiclar membrane (a purely mechanical factor)

The size difference between tympanic membrane and the stapes footplate does what?

the area of tympanic membrane is large-> gets translated into a small area on the stapes footplate : *the size difference amplifies the forces*

what is the motile response of outer hair cells?

the bending of the stereocilia of outer hair cells, leads to motile response, which amplifies and sharpens the movement of the basilar membrane...

characteristic frequency of basilar membrane:

the frequency to which that location on the membrane responds most readily

THe masked threshold is

the level where the white noise just barely prevents someone from hearing the tone

vibrations of the tympanic membrane travels to...

vibrations are transferred from the tympanic membrane to the auditory ossicles to the oval window The tympanic membrane touches the *maleus* (part of the ossicles)

place coding for frequency=

the tuning of type 1 auditory nerve fibers can be almost entirely accounted for by the frequency tuning of the basiclar membrane (a purely mechanical factor)

Why does frequency tuning curves have evidence for place code frequency?

type 1 auditory nerve fibers, that is when noise masker has center frequency at or near frequency of target tone, the masker activates type 1 nerve fibers in the region of the basilar membrane with the characteristic frequecny corresponding to frequency of target tone.... but as the center frequency of masker moves away from the target tone (to different frequency hz) then the nerve fibers of that region are freed up to respond to target tone.... when the masker is louder, it activates nearby auditory fibers including those sensitive to target tone, thus the curves have evidence for place coding frequency.

How to determine psychophysical frequency tuning curves in humans?

use the white noise/ target tone experiment - do pure tone at frequency of 1000hz, at low amplitude (10dB above absolute threshold)