Hearing part 3 Flashcards
What are the two theories for how we perceive sound?
Place and temporal theories of pitch perception
What does the place theory of pitch perception say?
Frequency of sound determines location of greatest movement along basilar membrane –> determines which auditory nerves have peak activity –> determines perceived pitch
What is an issue for place theory?
Effect of the missing fundamental
Why is the effect of the missing fundamental an issue for place theory?
Pitch is the same despite missing fundamental frequency of 100 Hz
No longer peak activity at a place for 100 Hz but same perceived pitch
What is another issue for place theory?
Amplitude modulation
What is amplitude modulation?
fluctuating level (amplitude) of sound at specific frequencies
How does amplitude modulation have an issue for place theory?
Amplitude modulation changes pitch perception despite same frequencies of sound
What does the temporal theory for pitch perception argue?
It doesn’t matter where along the basilar membrane is activated, it depends on the rate it is getting activated
What is the temporal theory of pitch perception?
timing or repetition rate of a sound is available even when the fundamental (200 Hz) is missing and with amplitude modulation – solves the issues of the place theory
According to the temporal theory of pitch perception, why do the sounds with the missing fundamental sound so similar?
it leads to phase locking still at 200 Hz because repetition is the same
What does the place theory of pitch perception depend on?
which auditory nerves are active - place along basilar membrane
What does the temporal theory of pitch perception depend on?
timing of when auditory nerves are active
Temporal pattern of activation
What is most important for pitch perception?
likely both location and timing of activation matters
What is the acronym for remembering the auditory pathway?
SONIC MG
What are the steps in the auditory pathway? Say where those nuclei are located?
Auditory nerve
Cochlear nuclei (medulla)
Superior olivary nucleus (pons)
Inferior colliculus (midbrain)
Medial Geniculate nucleus (thalamus)
Primary auditory cortex
What are the three parts of auditory cortex?
Core, belt, parabelt
Where is the primary auditory receiving area located? (what lobe)
temporal lobe
What is the core?
A1/ primary auditory cortex
What does the belt surround?
the core
Is the tonotopic map also represented in A1?
Yes
What is a tonotopic map?
arrangement based on length of cochlea from low to high frequency
Does the tonotopic mapping get repeated past primary auditory cortex?
yes
Where are pitch neurons located?
in primary auditory cortex
What did the study on pitch neurons in auditory cortex of marmoset monkeys do?
recorded from a single neuron and played different groups of harmonics of the fundamental frequency - each composition has the same repetition rate (at the missing fundamental)
What did the study on pitch neurons find?
neuron responds to groups of harmonics that present the same pitch (182 Hz) - pitch neurons respond to subjective perception of sound
What effect did the study on pitch neurons demonstrate?
the effect of the missing fundamental
What happened when they played a pure tone to the pitch neuron? (2 things it showed)
frequency selective (182 Hz/ fundamental frequency)
does not respond to individual harmonics (only groups) - only responds alone to the fundamental frequency –> need repetition at fundamental
What do pitch neurons respond to overall?
subjective perception of pitch
What else did the study on pitch neurons do?
Mapped out where pitch neurons are found
What do the large and small dots represent?
Small dots represent neurons that only respond to pure tones at characteristic frequencies (basic)
Large dots represent neurons responding to pitch of complex tones with missing fundamental (more subjective perception)
What is our subjective interpretation of sound frequency?
pitch
What are cochlear implants used for? What is still intact?
address hearing loss due to damaged or nonworking hair cells
auditory nerve still intact
How many people have cochlear implants?
300000
What happens with language skills from cochlear implants?
majority of deaf children who receive cochlear implants before 18 months of age had language skills similar to their hearing peers
What are the three external components of cochlear implants?
Microphone
Processor
Transmitter
What are the two internal components of cochlear implants?
Receiver and electrodes
What does the microphone do?
Transduces sounds into electricity
What does the processor do?
Analyzes sound into frequency bands
What does the processor simulate?
Simulates place specific activation of basilar membrane –> like cochlea
What does the transmitter do?
sends signals and power to internal implant
What does the receiver do?
Receives signals and power and transmits to electrodes
What do the electrodes do?
Stimulate different auditory nerves along length of cochlea
Where does the electrode array go?
implanted into the cochlea
What is the issue with the implantation of the cochlear implant?
doesn’t make it to the apex - can’t activate those locations
What would a spectogram look like for cochlear implants?
low frequencies missing
What are the three types of concerns about the cochlear implant?
ableist concerns, cultural concerns, developmental concerns
What are the ableist concerns of cochlear implants?
Cochlear implants imply that deafness is a medical disability that should
be cured
What are the cultural concerns of cochlear implants?
reduces the number of ASL speakers
What are the developmental concerns of cochlear implants?
brain must learn to interpret the signal as language - this process can be difficult and may lead to impaired language abilities compared to ASL
