Auditory Pathways

Question 1

Auditory information is received by what?

Answer 1

The cochlear nucleus by fibers in the cochlear nerve

These fibers then enter the brainstem at the cerebellopontine angle and split into ascending and descending bundles

Question 2

Where does the ascending bundle of the auditory pathway synapse?

Answer 2

At the anterior part of the anterior cochlear nucleus

Question 3

Where does the descending bundle of the auditory pathway synapse?

Answer 3

At the posterior part of the anterior cochlear nucleus and posterior part of the posterior cochlear nucleus

Question 4

Describe the monaural tract

Answer 4

Receives information about sounds at a single ear (routed to contralateral side)
Posterior cochlear nucleus -> posterior acoustic stria -> lateral lemniscus -> inferior colliculus -> medial geniculate nucleus -> primary auditory cortex

Question 5

The binaural tract manages information about what?

Answer 5

Differences between sounds at both ears

Handled by central pathways that receive, compare and transmit this input

Question 6

Describe the pathway for the binaural tract

Answer 6

Anterior cochlear nucleus (ACN) -> trapezoid body -> superior olivary nucleus (medial and lateral superior olivary nucleus) -> lateral lemniscus (central and posterior nucleus) -> inferior colliculus -> MGN -> primary auditory cortex

Question 7

What is the medial superior olivary nucleus (MSO) associated with?

Answer 7

Time

Question 8

What is the lateral superior olivary nucleus (LSO) associated with?

Answer 8

Intensity

Question 9

The central nucleus of the lateral lemniscus sends fibers to what?

Answer 9

The contralateral IC via the commissure of the inferior colliculus

Question 10

The posterior nucleus of the lateral lemniscus receives fibers from what?

Answer 10

The LSO

Also sends fibers across central nucleus of contralateral inferior colliculus

Question 11

What is central deafness?

Answer 11

Caused by damage to central pathways
Rarely results in ipsilateral deafness
Causes difficulty processing where sound is coming from and differentiating it

Question 12

What is sensorineural deafness?

Answer 12

Caused by damage to the cochlea or cochlear root of CN VIII
Damage can be due to abx, tumors or repeated exposure to loud noises
Results in ipsilateral deafness of structure affected

Question 13

What is conduction deafness?

Answer 13

Obstructed or altered transmission of sound to TM or through ossicle chain of middle ear
Damage to pinna -> cannot conduct sound properly
Excess ear wax
Damage to TM

Question 14

What provides blood supply to the cochlea and auditory nuclei of the pons and medulla?

Answer 14

Basilar artery

Question 15

What provides blood supply to the inner ear and cochlear nuclei?

Answer 15

Internal auditory (labyrinthe) artery (usually a branch of AICA)

Question 16

Occlusion of the internal auditory (labyrinthe) A results in what?

Answer 16

Monaural hearing loss
Can also damage fibers of facial nerve and pontine gaze center -> monaural hearing loss with ipsilateral facial paralysis and inability to look toward the side of the lesion

Question 17

What provides blood supply to the superior olivary olivary complex and lateral lemnsicus?

Answer 17

Short circumferential branches of basilar A

Question 18

What provides blood supply to the inferior colliculus?

Answer 18

Superior cerebellar and quadrigeminal arteries

Question 19

What provides blood supply to the medial geniculate bodies?

Answer 19

Thalamogeniculate arteries

Question 20

What provides blood supply to the primary auditory and association cortices?

Answer 20

Branches of M2 segment of middle cerebral A

Question 21

What is the dominant hemisphere?

Answer 21

Hemisphere that controls language

Question 22

What is Broca’s area?

Answer 22

Brodmann areas 44 and 45
Production of language (spoken, written, signed)
Also works with the frontal lobe which adds syntax, grammar and higher order motor aspects of speech

Question 23

What is Wenicke’s area?

Answer 23

Brodmann areas 39 and 40
Comprehension of language (spoken and signed)
Works along with parietal and temporal lobe which add lexicon (vocabulary) and attaching sounds to their meaning

Question 24

What is the arcuate fasciculus?

Answer 24

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

Question 25

Describe the non-dominant hemisphere

Answer 25

Typically the right hemisphere Responsible for non-verbal communication such as tone of voice, prosody (normal melodious intonation of speech that helps convey meaning), imparting emotional significance to language Contains areas analogous to Broca’s and Wernicke’s

Question 26

What is the area analogous to Broca’s?

Answer 26

Producing non-verbal communication (one’s own prosody of speech) Lesion results in motor aprosodia (inability to produce emotional indications with vocal inflection and facial gesturing)

Question 27

What is the area analogous to Wernicke’s?

Answer 27

Comprehending non-verbal communication (other’s prosody of speech) Lesion -> sensory aprosodia (ex. Not understanding when a person shrugs their shoulders they’re conveying idk)

Question 28

Describe the language pathway

Answer 28

Primary auditory cortex -> auditory association cortex -> Wernicke’s area -> arcuate fasciculus -> Broca’s area -> motor cortices

Question 29

What is the function of the primary auditory cortex?

Answer 29

Differentiates where and when sound is coming from

Question 30

What is the function of the auditory association cortex?

Answer 30

``` Classifies sound (with assistance from primary auditory cortex along with visual and somesthetic info) as what it is Ex. Hearing a lion roar and recognizing that is a lion making the noise ```

Question 31

What is the role of the motor cortices during that language pathway?

Answer 31

Send info to speech muscles to move accordingly

Question 32

What is auditory agnosia?

Answer 32

The inability to ID something but can still perceive it Caused by bilateral lesions to anterior superior temporal lobes Individual can perceive the sound but cannot describe the sound Ex. Someone talking in a language you don’t understand

Question 33

What is Broca’s aphasia?

Answer 33

Caused by tumors and occlusions of frontal M4 branches of MCA Expressive aphasia, difficulty turning concept/thought into meaningful sounds; difficulty writing; no repetition Pts are often very frustrated bc comprehension of speech is intact Severe forms are mute but can still swallow and breathe normally Typically use short phrases and often leave out non-essential words (responds mostly with um, yes or no)

Question 34

What is Wernicke’s aphasia?

Answer 34

Caused by occlusion of temporal and parietal M4 branches of the MCA as well as hemorrhages into the thalamus -> extends lateral and caudally to invade subcortical white matter Defect in comprehension of speech; unable to understand what is being said to them; unable to read (alexia); unable to write comprehensible language (agraphia) and display fluent paraphrasing speech; no repetition

Question 35

What is global aphasia?

Answer 35

Occlusion of left internal carotid or proximal portion of MCA (M1) —> results in damage to Broca’s and Wernicke’s areas Virtually complete loss of language

Question 36

What is conduction aphasia?

Answer 36

Interruptions of the connections linking the Broca’s and Wernicke’s areas (arcuate fasciculus) Comprehension is normal; speech is fluent but pt has difficulty translating what someone has said to him/her in appropriate reply Not able to repeat

Question 37

What is transcortical motor (pericentral) aphasia?

Answer 37

Caused by anterior watershed infarct (b/w anterior cerebral artery and middle cerebral artery) results in contralateral paresis and expressive language deficits similar to Broca’s Differs from Broca’s bc repetition is maintained

Question 38

What is transcortical sensory aphasia?

Answer 38

Caused by posterior watershed infarct (bw MCA and PCA) Results in partial visual field deficit and receptive language deficit similar to Wernicke’s Differs from Wernicke’s bc repetition is maintained

Question 39

What is mixed transcortical aphasia?

Answer 39

Similar to global aphasia -> some expressive and some comprehension deficits Differs bc repetition is maintained