Lecture 7: Auditory Pathway

Question 1

Injury to what area in the ascending pathway of the auditory system will result in unilateral sensorineural hearing loss?

Answer 1

• Cochlear nucleus
• Cochlear nerve
• The only 2 structures that if damagd will result in unilateral sensorineural hearing loss!

Question 2

What is the location of the first-order neurons in the auditory system, what nerve do they travel on and where do they synapse first?

Answer 2

• Spiral ganglion inside the Cochlea
• Leave via Cochlear nerve (CN VIII)
• Terminate in the Cochlear nucleus

Question 3

What are the different nuclei located within the Cochlear nucleus?

Answer 3

• Dorsal Cochlear Nucleus
• Ventral Posterior Cochlear Nucleus
• Anterior Ventral Cochlear Nucleus

Question 4

What are the axons sent from the dorsal cochlear nucleus and describe their route?

Answer 4

• Dorsal acoustic stria
• Decussate in the upper medulla and ascend in the contralateral, lateral lemniscus

Question 5

What are the axons from the ventral posterior cochlear nucleus and describe their route?

Answer 5

• Intermediate acoustic stria
• Decussate in the upper medulla, and ascend in the contralateral, lateral lemniscus

Question 6

What are the axons from the anterior ventral cochlear nucleus, what do they form and where do they go?

Answer 6

• Ventral acoustic stria
• Form the trapezoid body
• Terminate bilaterally in the superior olivary nucleus

Question 7

What is the only way that auditory information can get to the inferior colliculus?

Answer 7

Via the lateral lemniscus

Question 8

What is the connection between the cochlear nucleus and the superior olivary nucleus?

Answer 8

Ventral Acoustic Stria

Question 9

What nucleus of the auditory pathway contains axons from the 2nd, 3rd, and 4th order neurons?

Answer 9

Nucleus lateral lemniscus

Question 10

How are 2nd, 3rd, and 4th order neurons all able to reach the inferior colliculus in the auditory pathway?

Answer 10

• They can bypass the nucleus lateral lemniscus and go straight to the inferior colliculus via the lateral lemniscus tract
• Axons also go to the nucleus lateral lemniscus and can be housed there

Question 11

What are the locations of the 1st, 2nd, 3rd, 4th, and 5th order neurons in the auditory pathway?

Answer 11

1st = Spiral ganglion of Cochlea

2nd = Cochlear nucleus

3rd = Superior Olivary nucleus

4th = Nucleus lateral lemniscus

5th = Inferior colliculis

E COLI

Question 12

How do fibers get from the inferior colliculus to the medial geniculate nucleus?

Answer 12

Brachium of the inferior colliculus

Question 13

How do fibers get from the medial geniculate nucleus to the auditory cortex?

Answer 13

Sublenticular (auditory) radiations

Question 14

Where is the primary auditory cortex located?

Answer 14

Transverse and superior temporal gyri (AKA transverse gyrus of Heschl)

Question 15

Where is the auditory association cortex for processing and integration of sounds located?

Answer 15

Parieto-occipito-temporal (POT) association cortex and Wernicke’s area

Question 16

What is the direct link between the auditory association cortex (Wernicke’s) and Broca’s speech area in the frontal lobe?

Answer 16

Arcuate fasciculus

Question 17

What is Wernicke’s aphasia vs. Broca’s aphasia?

Answer 17

Wernickes: is a fluent apahasia where the patient can talk but give no meaning to what they are saying and will also have trouble comprehending spoken or written word

Broca’s: you can understand what people are saying to you, but will have trouble forming the words you want to say due to damage in the motor area of brain

Question 18

What is conduction aphasia?

Answer 18

• Patient can comprehend speech and is able to talk
• Have trouble repeating phrases

Question 19

What part of the auditory cortex is for high frequencies and which is for low frequencies?

Answer 19

- High frequencies are heard on the interior (medially)

- Low frequencies are heard more exteriorly (laterally)

Question 20

What are the functions of the medial and lateral portions of the Superior Olivary nucleus?

Answer 20

Medial SON: allows us to localize sound based off timing

Lateral SON: allows us to understand the intensity/loudness of sound

Question 21

What is Olivocochlear bundle and its function?

Answer 21

• Projection of efferent fibers from the SON which can dampen sound
• Connects to the outer hair cells in the organ of corti and can elongate them, in turn, pushing the tectorial membrane further away from inner hair cells and decreasing our ability to hear sounds
• Protective mechanism

Question 22

Which nucleus is the superior olivary nucleus able to send fibers to which directly controls muscles of the inner ear?

Answer 22

• Facial nucleus
• Fibers from the facial nucleus go to the inner ear to control the action of the stapedius m. (Stapedius = Seventh CN)

Question 23

What occurs with unilateral lesion of the central auditory pathway?

Answer 23

- Bilateral diminution of hearing

• Structures include: lateral lemniscus, inferior colliculus and brachium, and the medial geniculate body

Question 24

Lesions of the Primary Auditory Cortex result in what; are there hearing deficits?

Answer 24

• Difficulty localizing sounds and tone discrimination
• Does NOT result in hearing deficits

Question 25

Auditory agnosia is caused by lesions where; results in?

Answer 25

• Lesions in the auditory association cortex (POT)
• Inability to comprehend auditory information in general

Question 26

Which Brodmann’s area is Wernicke’s located in?

Answer 26

Brodmann’s area 22

Question 27

Which Brodmann’s area is Broca’s located in?

Answer 27

Area 44 and 45

Question 28

Although similar, what is the difference between Wernicke’s aphasia and auditory agnosia?

Answer 28

• In Wernicke’s a person is unable to comprehend the spoken or written word. Their speech patterns will demonstrate numerous word substitutions, new word creations, and talking a lot.
• In auditory agnosia a person has difficulty distinguishing speech from non-speech sounds (auditory information in general). Spoken and written language may remain intact.