Auditory Tracts (Dennis)

Question 1

Where do cochlear fibers enter into the brainstem?

Answer 1

Cerebellopontine angle

Question 2

How is auditory information received in the CNS

Answer 2

Fibers of the cochlear nerve (CN VIII) synapse in the cochlear nucleus. Fibers then split into ascending and descending bundles

Question 3

Where do the ascending and descending bundles of primary afferent CN VIII synapse?

Answer 3

• Ascending Bundle: Anterior subdivison of anterior/ventral cochlear nucleus
• Descending Bundle: Posterior subdvision of anterior/ventral cochlear nucleus and posterior part of posterior cochlear nucleus

Question 4

How is the cochlear nucleus distributed

Answer 4

1. Posterior/dorsal cochlear nucleus
2. Anterior/ventral cochlear nucleus

• Anterior part
• Posterior part

Question 5

What is the function of the monaural tract?

Answer 5

Information about sounds at a single ear routed to contralateral side

Question 6

Where are the primary cell bodies located in the monaural tracts?

Answer 6

Posterior/Dorsal Cochlear Nucleus in the Medulla

Question 7

Where does the monaural tract cross to the contralateral side?

Answer 7

Pons via posterior/dorsal acoustic stria

Question 8

What are the points of synapse in the monaural tracts?

Answer 8

1. Inferior Colliculus
2. Medial Geniculate Nucleus
3. Layer IV of Primary Auditory Cortex (Heschl’s Gyrus)

Question 9

What is the Route of the Monaural Tract

Answer 9

1. Fibers ascend from the posterior cochlear nucleus (medulla) and travel contralateral through the posterior acoustic stria.
2. Fibers then ascend through the lateral lemniscus and synapse at the inferior colliculus (midbrain).
3. Fibers then ascend through the branchium of the inferior colliculus and synapse at the medial geniculate nucleus (thalamus).
4. Fibers then finish by synapsing at the primary auditory cortex.

Question 10

What is the function of the binaural tract?

Answer 10

Manages information about differences between sounds at both ears

Role in localization of sound

Question 11

What are the points of synapse of the binaural tract?

Answer 11

1. Superior Olivary Nucleus
2. Inferior Colliculus
3. Medial Geniculate Nucleus
4. Layer IV of Primary Auditory Cortex (Heschl’s Gyrus)

Question 12

Where are the primary cell bodies for the Binural Tract and where do they synapse

Answer 12

Anterior Cochlear Nucleus

Synapse at both the Ipsilateral and Contralateral superior olivary complex

Question 13

What structure does the binaural fibers pass through to reach the contralateral superior olivary complex?

Answer 13

Trapezoid body in the pons

Question 14

Where is the first place that information from both ears converge

Answer 14

Superior Olivary Nucleus

Divided into medial & lateral parts

Question 15

What input does the Medial Superior olivary nucleus receive

Answer 15

Receives excitatory input from both the ipsilateral and contralateral anterior cochlear nucleus of both ears

Question 16

What input does the lateral superior olivary nucleus receive?

Answer 16

Excitatory input from ipsilateral anterior cochlear nucleus and inhibitory input from contralateral anterior cochlear nucleus

Question 17

Fibers from the medial and lateral superior olivary nuclei ascendind and syanpse ______, then ascend further to synapse at the ________

Answer 17

Lateral leminiscus

inferior colliculus

Question 18

Where does the central nucleus of the lateral leminiscus send fibers

Answer 18

Inferior colliculus

Question 19

Where does the posterior nucleus of the lateral leminiscus receive and send it’s fibers

Answer 19

Receives fibers from: lateral superior olivary nucleus

Sends some fibers: Inferior Colliculus on the opposite side via the posterior tegmental commissure

Question 20

Where do fibers of the binaural tract go to from the inferior colliculus

Answer 20

Ascend via the brachium of the inferior colliculus to synapse in the medial geniculate nucleus which then send fibers to the primary auditory cortex in the temporal lobe.

Question 21

What happens if there’s damage to the auditory central pathways

Answer 21

Rarely results in ipsilateral deafness. Results in difficulty processing where sound is coming from and differentiating it.

Question 22

What is sensorineural deafness

Answer 22

Ipsilateral deafness from damage to the cochlea or chochlear nerve root of CN VIII which can be due to antibiotics, tumors or repeated exposure to loud noises.

Question 23

What is conduction deafness

Answer 23

Obstructed or altered transmission of sound to the tympani membrane or through ossicle chain of middle ear which can be caused by damage to the pinna, damge to the tympanic membrane or excess ear wax

Question 24

What supplies the cochlea and auditory nuclei of pons and medulla?

Answer 24

Basilar Artery

Question 25

What is the blood supply to the inner ear and cochlear nuclei

Answer 25

Internal auditory (labyrinthine) artery (usually a branch of anterior inferioir cerebellar artery (AICA)

Question 26

Occlusion of what branch of the Basilar Artery will cause monaural hearing loss? What are the symptoms?

Answer 26

AICA *Can also damage Facial Nerve* monaural hearing loss with ipsilateral facial paralysis and inability to look toward the side of the lesion

Question 27

What supplies the superior olivary complex and lateral lemniscus?

Answer 27

Short circumferential branches of Basilar Artery

Question 28

What supplies the inferior colliculus?

Answer 28

Superior Cerebellar Artery Quadrigeminal Artery from PCA

Question 29

What supplies the medial geniculate body?

Answer 29

Thalamogeniculate Artery from PCA

Question 30

What supplies the primary auditory and association cortices?

Answer 30

M₂ segment of Middle Cerebral Artery

Question 31

What is the dominant hemisphere

Answer 31

The hemisphere that controls language which is typically the left in 95% of cases

Question 32

What is Broca's Area

Answer 32

* Area that controls production of **language** (spoken, written and signed). * Works with the **frontal lobe** which adds syntax, grammar and higher order motor aspects of speech

Question 33

What is Wernicke's Area

Answer 33

* Brain region that controls comprehension of language (spoken and signed). * Also works with parietal and temporal lobe which adds lexicon (vocabulary) and attaching sounds to their meaning.

Question 34

What is the Arcuate Fasciculus

Answer 34

Connecting network between Broca's and Wernicke's areas. Allows the combination of speaking coherently, understanding what is being said to us, and then responding appropriately.

Question 35

What is the non-dominant auditory hemisphere

Answer 35

Typically the right hemisphere. Responsible for **non-verbal** communication. * Tone of voice * Prosody (normal melodious intonation of speech that helps convery meaning) * Imparting emotional significance to language

Question 36

What is the Area Analogous to Broca's What would happen if there was a lesion to this area?

Answer 36

Brain area that allows for the production of non-verbal communication (one's own prosody of speech) Motor aprosodia (Example: wouldn't be able to be sarcastic)

Question 37

What is the Area Analogous to Wernicke's? What would happen to a lesion in this area?

Answer 37

Brain area that allows for the comprehension of non-verbal communication (other's prosody of speech) A lesion would cause sensory aprosodia (Example: wouldn't understand the meaning of a shrug)

Question 38

What is the language pathway and their function?

Answer 38

**1. Primary auditory cortex -** differentiates where and when sound is coming from **2. Auditory association cortex -** classifies the sound as what it is **3. Wernicke's area -** comprehending what is being said **4. Arcuate fasciculus -** Connects Wernicke's and Broca's **5. Broca's area -** Instructions for speech output **6. Motor cortices -** Send information to speech muscles to move accordingly

Question 39

What is Auditory Agnosia

Answer 39

Inability to identify something but still perceive it which is caused by bilateral lesions to the anterior superior temporal lobes. ## Footnote *Individual can perceive the sound, but cannot describe the sound (hearing someone speak another language that you don't understand)*

Question 40

Characteristics of Broca's Aphasia

Answer 40

* "Broken Speech" * Caused by tumors and occlusions of frontal M4 branches of middle cerebral artery * Can understand but have difficulty expressing themselves. * **No repetition** * Difficulty writing * Severe forms are mute

Question 41

Characteristics of Wernicke's Aphasia

Answer 41

* "Happy babblers" * Caused by occlusion of temporal and parietal M4 branches of the middle cerebral artery as well as hemorrhages into the thalamus --\> extends lateral and caudually to invade subcortical white matter * Defect in **comprehension** of speech * Unable to understand what is said to them * Unable to read, write comprehensible language and display fluent paraphasic speech * **No repetition**

Question 42

Characteristics of Global Aphasia

Answer 42

* Occlusion of left internal carotid or proximal portion of M1 middle cerebral artery resulting in damage to Broca's and Wernicke's * Loss of complete language

Question 43

What is conduction aphasia

Answer 43

* Interruptions of the connections linking Broca and Wernicke areas (arcuate fasciculus) * Comprehension is normal; speech is fluent, but patient has difficulty translating what someone has said to him/her in appropriate reply

Question 44

What is Transcorticol motor (Pericentral aphasia)

Answer 44

* Contralateral paresis and expressive language deficits similar to Broca's except that **repetition is maintained** * Caused by anterior watershed infract (anterior cerebral and middle cerebral artery)

Question 45

What is transcortical sensory (Pericentral aphasia)

Answer 45

* Partial visual field deficit and receptive language deficit similar to Wernicke's except that **repetition is maintained**. * Caused by posterior watershed infract (middle cerebral artery and posterior cerebral artery)

Question 46

What is mixed transcortical aphasia

Answer 46

Similar to global aphasia. Some expressive and some comprehension deficits. Difference is **repetition is maintained**.