Chapter 11: Auditory Brain Flashcards
The Auditory Nerve
- 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)
characteristic frequency
preferred frequency
Auditory Pathway: Right ear to Right Brain
Auditory nerve–> R. cochlear nucleus–>
R. superior olivary nucleus
–> R. inferior colliculus
R. medial geniculate nucleus (MGN)
Auditory Pathway: Right ear to Left Brain
Auditory nerve–>R. cochlear nucleus–>L. Trapezoid body–>
L. superior olivary nucleus
–>L. inferior colliculus
–> L.medial geniculate nucleus (MGN)
Descending pathways
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
Auditory cortex
Coding within the cortex is tonotopic
shows “frequency magnification”
damage does not affect detection or discrimination of pure tones
Ventral Stream
- 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
Dorsal Stream
- 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
3 Coordinantes
Azimuth coordinates -position left to right Elevation coordinates -position up and down Distance coordinates -position from observer
Binaural cues
location cues based on the comparison of the signals received by the left and right ears
Interaural intensity (or level) difference
- 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
Interaural time difference
- 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
Monaural Cue for Sound Location
- 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
Judging Distance
Loudness/amplitude
-familiarity
-inverse square law (Amplitude of sound decreases in proportion to the square of the distance to the source)
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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)
Auditory Scene
Auditory Scene Analysis
- the array of all sound sources in the environment
- process by which sound sources in the auditory scene are separated into individual perceptions
