Hearing Science Exam 2-- Quizzes

functions of the outer ear

protects middle ear, amplify mid frequencies, differentiates sounds from front and behind, helps localize sound

Interaural Time Differences

most relevant at low frequencies

Interaural Level Differences

most relevant at high frequencies

Which of the following contributes to the acoustic gain provide by the outer ear?

Pinna Flange, Ear Canal, Concha, Head, Torso and Neck

In measuring head related transfer functions (HRTFs) for the two ears, the sound source (input) at 4000 Hz is 60 dB SPL. The sound level measured at the entrance to the left ear canal is 45 dB SPL. The dB gain value of the left-ear HRTF is:

15 dB

In measuring head related transfer functions (HRTFs) for the two ears, the sound source (input) at 4000 Hz is 60 dB SPL.  The sound level measured at the entrance to the left ear canal is 45 dB SPL, and is 55 dB SPL at the entrance to the right ear. The interaural level difference at 4000 Hz is:

10 dB

Which of the three pathways for getting energy into the cochlea is most effective for normal hearing?

Ossicular chain vibration

Which of the middle-ear pressure amplification factors provides the most gain?

area transformer

Match the impedance factor with the most relevant frequency region

Low Frequencies: Stiffness

High Frequencies: Mass

Mid Frequencies: Damping

Which of the following is not a limit of the middle-ear acoustic reflex?

Only works to change the mass of the system

Identify whether these parts of the inner ear are part of the vestibular system, the auditory system, or both:

• Vestibular System: 

  • Saccule, Otolith Organs, Semicircular Canals

• Auditory System:

  • Organ of Corti, Cochlea

• Both:

  • Cranial Nerve VIII, Endolymph, Hair cells

Reissner's membrane

Separates the scala vestibuli from the scala media

Modiolus

The central axis around which the cochlear spiral winds

Basilar Membrane

Supports the organ of Corti

Organ of Corti

Contains the cochlear sensory hair cells

Helicotrema

The very apex of the cochlea

Hair cells

Sensory cells of the inner ear

Tectorial membrane

Gelatinous structure that sits atop the sensory hair cells

Which impedance factor varies along the basilar membrane and is the primary determinant of how resonant frequency changes along the length of the cochlea?

stiffness

scala media

Which scala contains the hairs (stereocilia) of the cochlear sensory cells?

Inner hair cells

which hair cells are closer to the modiolus

You observe that the motion of the basilar membrane is maximal 30 mm from the stapes.  If the basilar membrane responds to frequencies over the range from 20 to 20000 Hz, which of the following tones was most likely the stimulating tone?

75 Hz

A particular stimulus causes three places of maximal displacement of basilar-membrane motion.  What is most likely true about the stimulus?

It's a complex sound with three frequency components

The basilar membrane is _____ in the base of the cochlea compared to the apex, where the basilar membrane is _____.

narrower;wider

Which feature of the cochlea helps to establish its tonotopic (frequency-specific) organization?

Variations in basilar membrane stiffness

The basilar membrane is tonotopically organized, with low frequencies represented at the _____ and high frequencies represented at the _____.

apex,base

Because a traveling wave causes displacement at a range of locations on the basilar membrane, each location acts as a ______.

band pass filter

Inner hair cells are connected to the tectorial membrane and the basilar membrane, unlike the outer hair cells which are connected to the basilar membrane only.

false

Select all that apply to Type I afferent auditory neurons

comprise 95% of the auditory nerve, myelinated, innervate inner hair cells, larger

Select all that apply to Type II afferent auditory neurons

comprise 5% of the auditory nerve, smaller, unmyelinated, innervate outer hair cells

What motor protein changes configuration and causes outer hair cell length to change?

prestin

Which of the following structures helps to improve sound detection and frequency selectivity in the cochlea?

outer hair cells

Inner hair cells convey information to the brain via _____ neurons. Outer hair cells receive information from the brain via _____ neurons

afferent, efferent

match the independent-variable units with the neural response-plot type

Rate-Level function: dB SPL

Turning Curve: Hertz

Post-stimulus time histogram: milliseconds

Match the dependent variable units with the neural response plot type

Rate level function, post stimulus time, post stimulus time histogram:spike/second, turning curve: dB SPL

the full range of sound intensities can be coded by a single auditory nerve fiber

false

For which neural code is tonotopic organization most important? 

place code

What is the limit of phase locking in a single auditory nerve fiber?

5000 Hz

Match each auditory nerve fiber threshold range to the associated spontaneous rate

Low rate: high threshold

medium rate: medium threshold

high rate: low threshold

Which of the following are advantages of having multiple auditory nerve fibers respond to the same sound signal, rather than relying on a single fiber?

Allows for representation of a wider range of sound intensities

improves the reliability of sound encoding

preserves information about sound frequency when individual fibers reach their firing limit

enables more precise timing information to be conveyed through phase locking across fibers 

Which of the following characteristics of a neural threshold tuning curve changes with OHC loss?

Bandwidth, neural threshold

put the structures of the auditory pathway in order from bottom to top

cochlea, auditory nerve, cochlear nucleus, super olivary complex, lateral lemniscus,  inferior colliculus, medial geniculate body, auditory cortex

which of the following structures are organized into a core region and a belt region

auditory cortex, medial geniculate body, inferior colliculus

which of the following structures makes the first place where information from both ears is combined

super olivary complex

match the 2 subdivisions of the SOC with their description

LSO: better at processing interaural level differences, has high frequency bias

MSO: better at processing interaural time differences, has low frequency bias 

there is an ipsilateral bias along the auditory pathway 

false

the belt regions of the upper brain structure are tonotopically organized

false

what is the first brainstem structure on which afferent AN fibers synapse

cochlear nucleus

match the region with the type of information it processes 

auditory information: core regions of the upper brainstem structures

poly-sensory information: belt regions of the upper brainstem structures 

computing resonance frequency

v= speed of sound (305/ length of canal m)

How are ILDs created, why are they most prevalent at high frequencies  

differences in sound intensities arriving at 2 ears.Created by the acoustic shadow cast by the head. when sound hits the ear, it must travel around the head to get to the other ear. The head is the primary physical barrier w intensity reduction at the far ear. most prevalent at high frequencies because they have shorter wavelengths compared to head dimension. 

calculating for interaural time differnence

ITD= distance (m) / speed of sound (350) 

what is an HRTF (head related transfer function)

a measurement that describes how the outer ear, torso, and head transform a soundwave as it travels from sound source to eardrum. makes the brain able to localize sound. stimulates spatial hearing by filtering sounds for each ear.

3 mechanisms by which the ear provides pressure amplification 

1. area transformer— main contributor to middle ear impedance mismatch (25 dB, x17) 

2. lever transformer— lever action of middle ear bones (2 dB x1.3)

3. buckling motion— eardrum increases force transfer to malleus (6dB x2)

sequence of events when ear pops 

1. after ascent, pressure decreases

2. eardrum is pushed outward

3. hearing is reduced

4. ear pops (swallow/yawn)= eustachian tube opening

5. hearing returns to normal

why do middle ear pathologies create low frequency hearing loss

the involve increased stiffness (creating low freq hearing loss)

what scala is connected to sapes through oval window

scala vestibuli

what scala is bordered by reissners membrane , organ of corti, and stria vascularis

scala media

what 2 scala are connected by helicotrema 

scala vestibuli and scala tympani

what is meant by tonotopic representation

frequency sensitivity varies along the BM due to variations in resonance. spatial mapping of sound by frequency localization along the BM. maximal motion near base, low frequency at apex

label 16, 21, 2

oval window, stapes footplate, eustachian tube/ facial nerve

label D, E, F, G

tect. membrane, basilar membrane, scala tympani, OHC

label A,C,D,G,H,I,K,A

resissners membrane, tectorial membrane, spiral limbus, organ of corti, basilar membrane, spiral ligament, scala vascularis

what is the difference between DC and AC potential

DC— steady/non alternating, doesnt change with stimulus

AC— alternate at same frequency as sound stimulus , phase locked

where is endocochlear potential located, what is the normal resting rate

located in the scala media within the endolymph, resting potential is +80 mV maintained by the stra vascularis

what HCs have motile repsonses

OHCs have motile responses , fast motility is mediated by prestin

which hair cells send a majority of afferent messages to auditory nerve

IHCs

steps between stapes to neural impulses of ANF 

1. sound travels thru air as a vibration

2. vibration reaches ear, tympanic membrane opens

3. ossicles vibrate, stapes footplate pushes in and out on oval window

4. fluid in cochlea moves, BM vibrates at frequency of the sound

5. HCs are depolarized w/ upward motion of BM

6. auditory nerve sends info about sound that was heard to CNS 

ANF rate of discharge 

not silent— they have spontaneous activity

low SR < 0.5 spikes

medium SR >0.5 to 18 spikes

high SR many up to 100 spikes 

neural saturation

when a neuron has reached its maximal firing rate and cant increase its rate anymore

dynamic range vs spontaneous rate

inversely related—

high SR= low threshold, narrow range

low SR= high threshold, wide range

neural threshold turning curve 

threshold for each frequency to make neuron respond , shows lowest threshold and where its most sensitive, typically V shaped 

neural frequency response area

shows the firing rate of a neuron to many combinations of frequency and level

place code

freq of sound can be determined by noting which fiber fires the greatest relative discharge rate, place along BM and auditory nerve budle

temporal code 

timing of AN discharges are used to determine frequency of input stimulus 

volley theory

combining spikes across multiple fibers fills the temporal code , the time between spikes tells the brain about sound frequency

phase locking

ability to synchronize firing to a particular phase of a stimulus degrades above 5 kHz in ANFs. firing ANFs at a consistent phase of the stimulating sound waves cycle . for low freq sounds it can fire consistently and maintain timing w peaks of the sound wave. as freq increases, the cycles become too fast for the ANFs to fire a spike for every cycle

list components of central auditory system in order starting w auditory nerve

1. auditory nerve— sound from cochlea to brainstem

2. cochlear nucleus— processing

3. SOC (superior olivary cortex)— first binaural integration and localization

4. LL (lateral lemniscus)— temporal and spatial cues

5. IC (inferior colliculus)— first place for sensory info

6. MGB (medial geniculate body)— thalamic relay

7. auditory cortex— perceptual analysis and interpretation

core vs belt 

core= direct input and precise tonotopy, simple info 

belt= indirect input and broader frequency, complex

why are outer hair cells referred to as the “cochlear amplifier”

they help amplify low level sounds to increase sensitivity and sharpen tuning

which is an otoacoustic emission 

DPOAE— 2 main types of OAEs : distortion produced (pure and continuous) and transient evoked (clicks) 

what plot is used to measure threshold as a function of frequency

tuning curve, which illustrates auditory thresholds across varying frequencies.

a patient that has a middle ear pathology producing low frequency hearing loss would see an increase in what

stiffness

what mechanism does the ear canal use to help provide amplification

acoustic resonance — ear canal acts as a resonance tube to amplify sound pressure

what properties limits a single ANFs ability to encode intensity

limited dynamic range, spontaneous firing rate

what frequencies are most sensitive to ILDs

high frequencies

main function of inner hair cells

transduce signals from mechanical to electrical impulses

main function of outer hair cells

sensitivity and frequency selectivity