Chapter 11: Auditory Brain

Question 1

The Auditory Nerve

Answer 1

• 50, 000 fibers
• 95% from the 3500 inner hair cells
• 5% from the 12,000 outer hair cells
• like other cells we have learned about, each fiber has a limited range of frequencies that will evoke a response (tuning curve)

Question 2

characteristic frequency

Answer 2

preferred frequency

Question 3

Auditory Pathway: Right ear to Right Brain

Answer 3

Auditory nerve–> R. cochlear nucleus–>
R. superior olivary nucleus
–> R. inferior colliculus
R. medial geniculate nucleus (MGN)

Question 4

Auditory Pathway: Right ear to Left Brain

Answer 4

Auditory nerve–>R. cochlear nucleus–>L. Trapezoid body–>
L. superior olivary nucleus
–>L. inferior colliculus
–> L.medial geniculate nucleus (MGN)

Question 5

Descending pathways

Answer 5

Carry signals between auditory cortex
Modulate motile response
Protect ear from damage through acoustic reflex activation
Block task-irrelevant ascending auditory signals and pass task-relevant ones
feedback-related MGB activity correlates with the ability to discriminate different syllables

Question 6

Auditory cortex

Answer 6

Coding within the cortex is tonotopic
shows “frequency magnification”
damage does not affect detection or discrimination of pure tones

Question 7

Ventral Stream

Answer 7

• What or ventral stream starts in the anterior portion of the core and belt and extends to the prefrontal cortex
• It is responsible for identifying sounds

Question 8

Dorsal Stream

Answer 8

• Where or dorsal stream starts in the posterior core and belt and extends to the parietal and prefrontal cortices
• It is responsible for locating sounds

Question 9

3 Coordinantes

Answer 9

Azimuth coordinates 
-position left to right
Elevation coordinates 
-position up and down
Distance coordinates 
-position from observer

Question 10

Binaural cues

Answer 10

location cues based on the comparison of the signals received by the left and right ears

Question 11

Interaural intensity (or level) difference

Answer 11

• difference in sound pressure level reaching the two ears
• Reduction in intensity occurs for high frequency sounds for the far ear
• The head casts an acoustic shadow
• This effect is minimal for low frequency sounds

Question 12

Interaural time difference

Answer 12

• difference between the times sounds reach the two ears
• When the source is to the side of the observer, the times will differ
• This effect is minimal for high frequency sounds

Question 13

Monaural Cue for Sound Location

Answer 13

• The pinna and head affect the intensities of frequencies
• The difference is called the head-related transfer function (HRTF)
• This is a spectral cue since the information for location comes from the spectrum of frequencies

Question 14

Judging Distance

Answer 14

Loudness/amplitude
-familiarity
-inverse square law (Amplitude of sound decreases in proportion to the square of the distance to the source)
.
.
Spectral Cues
-“blurring” (reduction in relative loudness of higher frequency components of sound)
-Proportion of sound reflected from surfaces
-Doppler effect (The frequency of a sound emitted by a moving sound source is higher in front of the sound source than behind it)

Question 15

Auditory Scene

Auditory Scene Analysis

Answer 15

• the array of all sound sources in the environment

- process by which sound sources in the auditory scene are separated into individual perceptions

Question 16

Auditory Grouping

Answer 16

-Heuristics that help to perceptually organize stimuli
>Location - a single sound source tends to come from one location and to move continuously
>Similarity of timbre and pitch - similar sounds are grouped together
>Auditory stream segregation - separation of stimuli into different perceptual streams

Question 17

Interactions Between Vision and Sound

Answer 17

• Visual capture or the ventriloquist effect - an observer perceives the sound as coming from the seen location rather than the source for the sound
• Balls moving without sound appeared to move past each other
• Balls with an added “click” appeared to collide

Question 18

Simultaneous Sounds: 4

Answer 18

Grouping by Temporal Proximity
Grouping by Frequency Similarity
Grouping by Harmonic Coherence
Grouping by Synchrony or Asynchrony