auditory I-III

Question 1

What is intensity of sound

Answer 1

Perceived loudness, measured by the pressure at the peak of compression. The more forcefully air is compressed, the more intense the sound. Measured as decibels of sound pressure level (dB SPL) on a logarithmic scale

Question 2

How are dB SPL measured/calculated

Answer 2

dB SPL = 20 x log [p1/ 20 x 10^-6 Newtons/m2], where p1 is the pressure (N/m2) of the tested sound

Question 3

what is rarefaction

Answer 3

the opposite of compression- becoming less dense

Question 4

What is frequency of sound

Answer 4

The number of times per second that a sound wave reaches the peak of rarefaction (or compression). Measured in Hertz (cycles/sec). Aka pitch.

Question 5

How is the wavelength of sound calculated

Answer 5

wavelength= velocity/frequency

Question 6

2. What is auditory threshold, how is it measured in the audiogram?

Answer 6

Audiologists quantify hearing loss by determining for
each ear, and at different frequencies the smallest dB SPL that a subject can just detect (called the threshold). The threshold is represented on the audiogram (dB SPL vs frequency) as a curveAudiologists quantify hearing loss by determining for
each ear, and at different frequencies the smallest dB SPL that a subject can just detect (called the threshold). The threshold is represented on the audiogram (dB SPL vs frequency) as a curveAudiologists quantify hearing loss by determining for
each ear, and at different frequencies the smallest dB SPL that a subject can just detect (called the threshold). The threshold is represented on the audiogram (dB SPL vs frequency) as a curveAudiologists quantify hearing loss by determining for
each ear, and at different frequencies the smallest dB SPL that a subject can just detect (called the threshold). The threshold is represented on the audiogram (dB SPL vs frequency) as a curveAudiologists quantify hearing loss by determining for
each ear, and at different frequencies the smallest dB SPL that a subject can just detect (called the threshold). The threshold is represented on the audiogram (dB SPL vs frequency) as a curve

Question 7

Most common cause of hearing loss and what type of sound is lost

Answer 7

age- we lose high frequency hearing (presbycusis) which is most problematic for perception of speech (b/c consanants such as t, p, s, f are distinguished by high frequency components)

Question 8

Transmission of sound to the cochlea takes place through __________ means

Answer 8

mechanical

Question 9

components of the external ear

Answer 9

composed of the pinna and external auditory meatus (ear canal) bounded by the tympanic membrane

Question 10

components of the middle ear

Answer 10

3 middle ear bones, malleus, incus and stapes

Question 11

components of the inner ear

Answer 11

cochlea and the semicircular canals

Question 12

pinna function

Answer 12

funnels sound toward opening of auditory meatus, thus providing some directional amplification, filters incoming sound wave providing cues to spatial location of the sound.

Question 13

Tympanic membrane function

Answer 13

rarefaction causes it to bulge out, and compression to press in. At this point the airborne pressure wave is transformed into a vibration of the bones in the ossicular chain, which are connected mechanically to the tympanic membrane.

Question 14

Which part of the ear functions as an impedance matcher- explain

Answer 14

Middle ear- the air filled outer ear has low impedence and the water filled inner ear has high impedance, resulting in an impedence mismatch. The middle ear bones translate the airborne pressure waves into motion of the fluid of the inner ear, alleviating the impedance mismatch. Since Pressure= Force/ area, increased force or decreased area will increase pressure. Stapes footplate is 20 times smaller than the tympanic membrane and the orientation of the bones creates a lever action which results in larger force.

Question 15

4. Understand the difference between sensorineural and conductive hearing loss.

Answer 15

Conductive: mechanical transmission of sound energy through middle ear is degraded. Sensorineural: damage to or loss of hair cells/nerve fibers.

Question 16

Causes of conductive hearing loss

Answer 16

1) filling of the middle ear with fluid during otitis media (i.e., ear infection); 2) otosclerosis, in
which arthritic bone growth impedes the movement of the ossicles; 3) malformations of the ear canal (atresia), including “swimmer’s” and “cauliflower” ear; 4) perforation/rupture of the tympanic membrane; 5) interruption of the ossicular chain; 6) static pressure in middle ear. Losses of 10-60 dB can occur in these cases.1) filling of the middle ear with fluid during otitis media (i.e., ear infection); 2) otosclerosis, in
which arthritic bone growth impedes the movement of the ossicles; 3) malformations of the ear canal (atresia), including “swimmer’s” and “cauliflower” ear; 4) perforation/rupture of the tympanic membrane; 5) interruption of the ossicular chain; 6) static pressure in middle ear. Losses of 10-60 dB can occur in these cases.1) filling of the middle ear with fluid during otitis media (i.e., ear infection); 2) otosclerosis, in
which arthritic bone growth impedes the movement of the ossicles; 3) malformations of the ear canal (atresia), including “swimmer’s” and “cauliflower” ear; 4) perforation/rupture of the tympanic membrane; 5) interruption of the ossicular chain; 6) static pressure in middle ear. Losses of 10-60 dB can occur in these cases.1) filling of the middle ear with fluid during otitis media (i.e., ear infection); 2) otosclerosis, in
which arthritic bone growth impedes the movement of the ossicles; 3) malformations of the ear canal (atresia), including “swimmer’s” and “cauliflower” ear; 4) perforation/rupture of the tympanic membrane; 5) interruption of the ossicular chain; 6) static pressure in middle ear. Losses of 10-60 dB can occur in these cases.1) filling of the middle ear with fluid during otitis media (i.e., ear infection); 2) otosclerosis, in
which arthritic bone growth impedes the movement of the ossicles; 3) malformations of the ear canal (atresia), including “swimmer’s” and “cauliflower” ear; 4) perforation/rupture of the tympanic membrane; 5) interruption of the ossicular chain; 6) static pressure in middle ear. Losses of 10-60 dB can occur in these cases.

Question 17

Causes of sensorineural hearing loss

Answer 17

Occurs from damage to or the loss of hair cells and or nerve fibers. Common causes are 1) excessively loud sounds (iPod!!); 2) exposure to ototoxic drugs (diuretics, aminoglygocide antibiotics, aspirin, cancer therapy drugs); and 3) age (presbycusis).

Question 18

how do we distinguish conductive from sensorineural hearing loss on exam

Answer 18

in Conductive hearing loss, a tuning fork pressed against the bone will be heard (because the bone transmits the sound past the middle ear into fluid filled inner ear), while tuning fork in the air will not be heard

Question 19

components of the cochlea

Answer 19

in cross section, the cochlea contains 3 fluid filled membranous compartments scala vestibuli, scala media and scala tympani. scala media and tympani are separated by basilar membrane (but connected by the helicotrema, a hole in the BM at the apex of the cochlea to relieve pressure), and sitting within the media and on top of the basilar membrane is the organ of Corti containing inner hair cells

Question 20

Function of cochlea

Answer 20

inner hair cells transduce sound into electrical signals.

Question 21

describe how sound is transmitted to electrical signals in the inner ear

Answer 21

sound wave moves the basilar membrane, which in turn moves the inner hair cells in the organ of corti

Question 22

5. How does sound elicit movement of the BM?

Answer 22

As sound waves enter the inner ear, the oval window is compressed by the ossicles and bulges into the scala vestibulli, causing the basilar membrane to bulge into the scala tympani, then the compression in the scala tympani results in bulging of the round window into the middle ear. During rarefaction, the opposite will happen (ie. round window bulges towards scala tympani and oval window bulges out towards middle ear)

Question 23

What is the tonotopic map?

Answer 23

At the base of the cochlea (the end near the oval
and round windows), the BM is thinner, narrower and more rigid, while at the apex the BM is more flexible, wider and thicker. The BM vibrates to high frequencies towards the base and to low frequencies towards the apex, creating a tonotopic map along the length of the BM. At the base of the cochlea (the end near the oval
and round windows), the BM is thinner, narrower and more rigid, while at the apex the BM is more flexible, wider and thicker. The BM vibrates to high frequencies towards the base and to low frequencies towards the apex, creating a tonotopic map along the length of the BM. At the base of the cochlea (the end near the oval
and round windows), the BM is thinner, narrower and more rigid, while at the apex the BM is more flexible, wider and thicker. The BM vibrates to high frequencies towards the base and to low frequencies towards the apex, creating a tonotopic map along the length of the BM. At the base of the cochlea (the end near the oval
and round windows), the BM is thinner, narrower and more rigid, while at the apex the BM is more flexible, wider and thicker. The BM vibrates to high frequencies towards the base and to low frequencies towards the apex, creating a tonotopic map along the length of the BM.

Question 24

Why do hair cells located along the length of the BM respond maximally to different frequencies?

Answer 24

Due to the tonotopic map: Each IHC will respond best to a certain frequency determined by the mechanical properties of the BM at that particular location. ie. IHC at the apex will vibrate more with a low frequency sound b/c the BM at this location vibrates more to low frequency sounds. Thus the primary stimulus attribute that is mapped along the cochlea is sound frequency (and intensity).

Question 25

6. How does the IHC respond to bending of the stereocilia?

Answer 25

The apical surface of a hair cell has an array of stereocilia varying in length. Movement of the stereocilia bundle towards the longest stereocilia causes depolarization of the hair cell, movement towards the smallest stereocilia causes hyperpolarization.

Question 26

What is the normal membrane potential of the hair cell

Answer 26

It is -50mV. It is never at rest (ie. At the K eq potential

Question 27

What are the properties of the transduction channels located at the tips of the stereocilia?

Answer 27

Bending of the stereocilia results in altered gating of transduction channels located near the tips of the individual hairs.The transduction channel is a non-specific cation channel that is voltage-insensitive. The apical end of the IHC is in the scala media which is filled with K rich, Na poor endolymph. The basal end of the IHC is near the basilar membrane in the scala tympani which is filled wtih High Na low K perilymph.

Question 28

How is the endolymph created

Answer 28

The stria vascularis, an epithelium on the side of the scala media actively pumps K+ into the endolymph maintaining a high K+ concentration

Question 29

What is the endonuclear potential

Answer 29

Active pumping of K+ by the stria vascularis results in a positive potential inside the scala media. This potential, the endocochlear potential, has a magnitude of +80 mV (endolymph positive with respect to perilymph)

Question 30

collapse of the endonuclear potential causes what. Give example

Answer 30

sensorineural hearing loss b/c there is a loss in driving force for transduction. Mutation in gap junction subunit connexin 32 causes collapse of endonuclear potential by reducing active transport of K in the stria vascularis. This is major cause of congenital deafness

Question 31

which ion is involved in hair cell depolarization

Answer 31

K influx

Question 32

describe opening/closing of the hair cell transducer channel

Answer 32

Tip links (thread-like connections) attach the apex of each sterocilium to the shank of the next. Bending the stereocilia towards the longer cilia causes the tip links to pull on the tops of the cilia, mechanically opening the channels, causing depolarization. When the bundle is pushed towards the shortest stereocilia, the channels are closed and the cell is hyperpolarized.

Question 33

hair cell membrane potential follows the movement of what?

Answer 33

Basilar membrane- up to 3kHz, any frequency of sound will cause an oscillating membrane potential of the same frequency. Above 3KHz there is temporal integration of the membrane potential leading to large depolarizations

Question 34

How does BM movement translate into hair bundle displacement

Answer 34

The hair cells are attached at the apical end to the tectorial membrane (on the scala media side) and at the basal end are attached to the basilar membrane (on the scala tympani side). The BM and TM are attached at different points on cochlear wall, so their pivot points are different. As the membranes move up-down together, lateral shearing forces occur btw the membranes, so the ciliary bundles are pushed from side to side as a consequence of the shearing.

Question 35

List steps in transduction of sound energy into electrical signals

Answer 35

Vibrations of eardrum > ossicles vibrate > Vibrations of the stapes on oval window cause traveling waves in cochlear fluids> vertical displacement of the basilar and tectorial membranes > shearing force between membranes bends the ciliary bundles of the hair cells > Ciliary bending leads to depolarization or hyperpolarization of the membrane potential >
increased or decreased rates of transmitter release >
Transmitter (aspartate or glutamate) causes depolarization of the afferent auditory nerve fiber > action potentials sent to second order neurons in the brainstem.Vibrations of eardrum > ossicles vibrate > Vibrations of the stapes on oval window cause traveling waves in cochlear fluids> vertical displacement of the basilar and tectorial membranes > shearing force between membranes bends the ciliary bundles of the hair cells > Ciliary bending leads to depolarization or hyperpolarization of the membrane potential >
increased or decreased rates of transmitter release >
Transmitter (aspartate or glutamate) causes depolarization of the afferent auditory nerve fiber > action potentials sent to second order neurons in the brainstem.Vibrations of eardrum > ossicles vibrate > Vibrations of the stapes on oval window cause traveling waves in cochlear fluids> vertical displacement of the basilar and tectorial membranes > shearing force between membranes bends the ciliary bundles of the hair cells > Ciliary bending leads to depolarization or hyperpolarization of the membrane potential >
increased or decreased rates of transmitter release >
Transmitter (aspartate or glutamate) causes depolarization of the afferent auditory nerve fiber > action potentials sent to second order neurons in the brainstem.

Question 36

discuss innervation of hair cells. What are the types

Answer 36

inner and outer hair cells are innervated by VIIIth cranial nerve, or spiral ganglion. They are called auditory nerve fibers. Type I ANFs innervate the IHCs and are myelinated and Type II innervate the OHCs and are not myelinated. A single IHC is innervated by 10-30 type I ANFs, while a single type II ANF innervates ~10 different OHCs.

Question 37

outer hair cells types of channels

Answer 37

OHCs bear stereocilia with mechanotransducing channels. However, unlike IHCs, OHCs are poorly
innervated by afferent ANFs, and are not thought to act as transducers. Rather, the efferent innervation from the central auditory system act upon OHCs to amplify the movements of the BM. OHCs respond
to changes in voltage with a change in length – they are “electromotileOHCs bear stereocilia with mechanotransducing channels. However, unlike IHCs, OHCs are poorly
innervated by afferent ANFs, and are not thought to act as transducers. Rather, the efferent innervation from the central auditory system act upon OHCs to amplify the movements of the BM. OHCs respond
to changes in voltage with a change in length – they are “electromotileOHCs bear stereocilia with mechanotransducing channels. However, unlike IHCs, OHCs are poorly
innervated by afferent ANFs, and are not thought to act as transducers. Rather, the efferent innervation from the central auditory system act upon OHCs to amplify the movements of the BM. OHCs respond
to changes in voltage with a change in length – they are “electromotile

Question 38

How are outer hair cells electromotile and what is the resuult of this characteristic

Answer 38

OHCs have a motor protein, prestin, which is voltage sensitive. In response to sound, the motor proteins change the length of the hair cell and because th OHCs are attached to the BM, the chang in length of the OHC pulls the BM towards or away from the tectorial membrane, changing the mechanical frequency selectivity of the BM

Question 39

function of medial olivocochlear neurons

Answer 39

These are efferent neurons that innrvate the OHCs. The sense the frequency and intensity of sound and act as feed-back control devices to change the
cochlear sensitivity via the OHCs. The motor proteins of the OHC are frequency tuned as well, so that the OHC will undergo th largest length changes when stimulated by the appropriate frequency. These are efferent neurons that innrvate the OHCs. The sense the frequency and intensity of sound and act as feed-back control devices to change the
cochlear sensitivity via the OHCs. The motor proteins of the OHC are frequency tuned as well, so that the OHC will undergo th largest length changes when stimulated by the appropriate frequency. These are efferent neurons that innrvate the OHCs. The sense the frequency and intensity of sound and act as feed-back control devices to change the
cochlear sensitivity via the OHCs. The motor proteins of the OHC are frequency tuned as well, so that the OHC will undergo th largest length changes when stimulated by the appropriate frequency.

Question 40

7. What is understood by the “cochlear amplifier”?

Answer 40

the OHC enhances the movement of the BM
in a frequency-dependent manner, which results in a larger and sharper response of the BM to pure tone soundsthe OHC enhances the movement of the BM
in a frequency-dependent manner, which results in a larger and sharper response of the BM to pure tone soundsthe OHC enhances the movement of the BM
in a frequency-dependent manner, which results in a larger and sharper response of the BM to pure tone sounds

Question 41

clinical importance of the cochlear amplifier

Answer 41

sensorineural deafness can be caused by damage of OHCs. 1. Ototoxic antibiotics, such as streptomycin and gentamycin, can block the transduction channel of the OHCs and, with prolonged action, can kill them resulting in deafness. OHCs are more sensitive to these ototoxic antibiotics than IHCs. 2. OHCs are more sensitive than IHCs to damage due to prolonged exposure to loud sounds.

Question 42

What are otoacoustic emissions

Answer 42

The active OHCs can also create sounds, the so-called otoacoustic emissions (OAEs). Spontaneous or sound evoked movements of the OHCs set into motion the BM, which essentially causes the tympanic membrane to act as a loudspeaker. Miniature microphones placed in the ear canal can pick up these faint sounds created in the cochlea. OAEs are one of the main methods by which the hearing in newborn infant is tested. Lack of normal OAEs in infants can indicate sensorineural hearing loss.

Question 43

what is frequency tuning

Answer 43

When number of Action potentials fired by a single ANF is plotted against sound frequency, there is a peak called the characteristic frequency. This is th frequency at which that fiber is maximally sensitive, and higher or lower frequencies result in fewer APs per second. This frequency tuning of ANFs arises directly from the mechanical frequency selectivity of the BM.

Question 44

How is frequency and intensity encoded for in ANFs for high frequency sounds

Answer 44

frequency of sound is partly encoded by the place along the cochlea where the afferent fiber innervates an IHC. sound intensity is encoded via increases in the rate at which the neuron fires action potentials as the SPL is increased (rate code)

Question 45

How is frequency and intensity encoded for in ANFs for low frequency sounds

Answer 45

ANFs “phase lock” their action potentials. They tend to fire action potentials only at particular phases (i.e., compression or rarefaction) of the ongoing sound waveform. Phase locking in ANFs results directly from the oscillating membrane potential of the IHCs and the tendency for IHCs to release excitatory neurotransmitter only during the depolarizing phase. Behaviorally, we use the temporal pattern of action potentials in ANFs to determine the “pitch” of sounds with frequencies below ~1 kHz.

Question 46

compare perceptions of loudness and pitch

Answer 46

loudness= rate coding. Pitch: temporal coding of timing (phase locking)

Question 47

auditory neuropathy

Answer 47

Type of sensorineural hearing disorder that is not necessarily accompanied by hearing loss. results from some problem with neural transmission from IHC to ANFs, or in the ANF function itself. Patients present with normal OAEs and even normal tone thresholds. One problem appears to be that ANFs have lost the ability to phase lock, leading to deficits in discriminating or even understanding speech

Question 48

9. Describe the anatomical pathway for the auditory system in the brainstem. Where do axons decussate in this pathway?

Answer 48

ANF collects sound info at cochlea > cell body in spiral ganglion > axons form auditory portion of VIIIth nerve > bifurcate upon entering brainstem > 1. ventral cochlear nucleus or 2. dorsal cochlear nucleus (both in inferior cerebellar peduncles) > some axons cross midline in the dorsal acoustic stria (from DCN) or trapezoid body (from VCN) in mid pons > some fibers synapse at superior olive in mid pons, some continue without synapsing > fibers regroup as lateral lemniscus and ascend> some fibers synapse in nucleus of lateral lemniscus in pons-midbrain junction, others coninue on > inferior colliculus of midbrain

Question 49

What neurons are located in the superior olivary nucleus

Answer 49

medial olivocochlear neurons- these feed back to the OHCs

Question 50

Discuss consequence of unilateral lesions rostral and caudal to the cochlear nuclei

Answer 50

Because some axons from cells in the cochlear nucleus join the ipsilateral lateral lemniscus while
others join the contralateral lateral lemniscus, unilateral lesions rostral to the cochlear nuclei do not produce unilateral deafness, whereas lesions caudal to and including the Cochlear Nuclei produce unilateral deafness. Lesions central to Cochlear Nuclei are often accompanied by deficits in sound source localization Because some axons from cells in the cochlear nucleus join the ipsilateral lateral lemniscus while
others join the contralateral lateral lemniscus, unilateral lesions rostral to the cochlear nuclei do not produce unilateral deafness, whereas lesions caudal to and including the Cochlear Nuclei produce unilateral deafness. Lesions central to Cochlear Nuclei are often accompanied by deficits in sound source localization

Question 51

9. Describe the anatomical pathway for the auditory system in the diencephalons and cerebral cortex.

Answer 51

Inferior colliculus (midbrain) receives input from cochlear nuclei and pontine nuclei (nuclei of superior olive) > fibers project mainly to ipsilateral medial geniculate where they synapse (thalamus), but some to contralateral inferior colliculus and medial geniculate > primary auditory cortex (A1, in superior temporal gyrus) via auditory radiations. > Regions of auditory cortex are linked by association fibers (on same side) an anterior commisure (for opposite sides)

Question 52

two functions of auditory system

Answer 52

determine what it was in the environment that produced a sound while the second is to determine where in space the sound occurred

Question 53

How do we determine what a sound is?

Answer 53

This is done using a combination of both rate coding of sound intensity and temporal coding (phase locking) of the periodicity of sounds. The population of ANFs, each ANF sensitive to a different range of frequencies (frequency tuning curve), acts essentially as a spectrum analyzer; measuring what frequencies are present, their intensities, and their relative times of arrival. This information is preserved in the
responses of the ventral cochlear nucleus neurons and ultimately transmitted to the auditory cortex where the pattern of neural activity is perceived and recognized as speech.This is done using a combination of both rate coding of sound intensity and temporal coding (phase locking) of the periodicity of sounds. The population of ANFs, each ANF sensitive to a different range of frequencies (frequency tuning curve), acts essentially as a spectrum analyzer; measuring what frequencies are present, their intensities, and their relative times of arrival. This information is preserved in the
responses of the ventral cochlear nucleus neurons and ultimately transmitted to the auditory cortex where the pattern of neural activity is perceived and recognized as speech.

Question 54

List 3 main acoustical cues for sound source localization

Answer 54

Interaural time delays, interaural level differences, and monaural spectral shape

Question 55

What are interaural time delays

Answer 55

Sound will arrive at each ear at different times, giving a clue as to where the sound came from

Question 56

What are interaural level differences

Answer 56

For sounds of high frequency (short wavelength), the head creates an acoustic shadow for the far ear because sounds with wavelengths the diameter of the head and smaller are refelcted off the near side of the head, attenuating the sound arriving at the ear farthest from the source.

Question 57

What are monaural spectral shapes

Answer 57

Help with localization of source elevation and in distinguishing btw sources in front of or behind observer. Direction and frequency dependent reflection and diffraction of pressure waveforms by pinna result in broadband spectral patterns, shapes, that change with location.

Question 58

Auditory neuropathy and localization

Answer 58

Patients with auditory neuropathy cannot use ITDs for sound localization because ITD coding relies on phase-locking, but can use ILDs, which use rate coding

Question 59

Where are interaural time delays and interaural level differences processed

Answer 59

ITDs: medial superior olive. ILDs: lateral superior olive

Question 60

Describe pathway of interaural time delays

Answer 60

ANFs send info to anteroventral cochlear nucleus > phase-locked neural responses carrying info on times of occurrence arrive at medial superior olive nucleus > MSO neurons behave like coincidence dtectors, responding maximally only when AP’s from L and R ears arrive simultaneously > AVCN axons form delay lines due to diff in neural path lengths (from ITD delays)

Question 61

When are ITDs most useful

Answer 61

for localization of low frequency sounds (<1.5kHz) where phase locking is best.

Question 62

Describe pathway of interaural level differences

Answer 62

ipsilateral ear input is conveyed via ANF synapses with AVCN cells which send an excitatory projection to ipsilateral lateral superior olive. Contralateral ear input comes from the ACVN but projects across midline to neurons of the medial nucleus of trapezoid body. AVCN cells synapsing on MNTB neurons forms the massive calyx of Held. MNTB neurons are glycinergic, so their projection to the LSO is inhibitory. The combo of ipsilateral excitation and contralateral inhibition allow LSO neurons to encode ILDs by a rate code (number of AP’s is proportional to sPL of the sound). LSO neurons then send excitatory projections to the contralateral dorsal nucleus of lateral lemniscus and inferior colliculus to acheive contralateral representation

Question 63

When are ILDs most useful

Answer 63

for localization of high frequency sounds

Question 64

List all the nuclei that converge on the inferior colliculus

Answer 64

cochlear nucleus, MSO, LSO, dorsal nucleus of lateral lemniscus

Question 65

Neurons at the level of the inferior colliculus represents sounds in the ipsilateral or contralateral hemisphere? Why

Answer 65

contralateral- the right IC represents sound sources on the left side of the body. B/c neurons from the MSO, LSO and DCN reconverge at the contralateral IC

Question 66

Clinical consequence of unilateral lesions above the IC, in the IC,

Answer 66

unilateral lesions in the IC or above result in deficits in sound source localization for sources contralateral to the lesion. And because the IC is heavily innervated by neurons from both ears, unilateral lesions at the IC or more central do not result in unilateral deafness.

Question 67

What does the medial geniculate body connect with

Answer 67

The MGB projects to the amygdala (auditory fear conditioning), then to the auditory cortical areas in the superior temporal gyrus.

Question 68

Primary auditory cortex layout

Answer 68

This is broadmanns area 41- arranged in a tonotopic map with neurons responding to lower frequencies located anteriorly and neurons responding to higher frequencies more posterior.

Question 69

Secondary auditory cortex

Answer 69

Broadmanns area 42- surrounds primary auditory cortex and includes Wernikes area (cortical area for understanding and processing spoken language)

Question 70

Damage to Wernikes area results in…

Answer 70

wernikes aphasia. General impairment in language comprehension but not language production.

Question 71

brocas area function

Answer 71

formation of spoken language